Fix Dark eldritch issue with alertorderserializer

Co-authored-by: metalgearsloth <31366439+metalgearsloth@users.noreply.github.com>

MSBuild/Robust.Engine.Version.props

@@ -1,4 +1,4 @@
 <Project>
     <!-- This file automatically reset by Tools/version.py -->
-    <PropertyGroup><Version>0.8.41</Version></PropertyGroup>
+    <PropertyGroup><Version>0.8.67</Version></PropertyGroup>
 </Project>

Robust.Analyzers/Diagnostics.cs

@@ -1,10 +1,14 @@
 using Microsoft.CodeAnalysis;
 
-namespace Robust.Generators
+namespace Robust.Analyzers;
+
+public static class Diagnostics
 {
-    public static class Diagnostics
-    {
-        public static SuppressionDescriptor MeansImplicitAssignment =>
-            new SuppressionDescriptor("RADC1000", "CS0649", "Marked as implicitly assigned.");
-    }
+    public const string IdExplicitInterface = "RA0000";
+    public const string IdSerializable = "RA0001";
+    public const string IdFriend = "RA0002";
+    public const string IdExplicitVirtual = "RA0003";
+
+    public static SuppressionDescriptor MeansImplicitAssignment =>
+        new SuppressionDescriptor("RADC1000", "CS0649", "Marked as implicitly assigned.");
 }

Robust.Analyzers/ExplicitInterfaceAnalyzer.cs

@@ -24,14 +24,14 @@ namespace Robust.Analyzers
             SyntaxKind.OverrideKeyword
         };
 
-        public const string DiagnosticId = "RA0000";
-
-        private const string Title = "No explicit interface specified";
-        private const string MessageFormat = "No explicit interface specified";
-        private const string Description = "Make sure to specify the interface in your method-declaration.";
-        private const string Category = "Usage";
-
-        [SuppressMessage("ReSharper", "RS2008")] private static readonly DiagnosticDescriptor Rule = new DiagnosticDescriptor(DiagnosticId, Title, MessageFormat, Category, DiagnosticSeverity.Warning, isEnabledByDefault: true, description: Description);
+        [SuppressMessage("ReSharper", "RS2008")] private static readonly DiagnosticDescriptor Rule = new(
+            Diagnostics.IdExplicitInterface,
+            "No explicit interface specified",
+            "No explicit interface specified",
+            "Usage",
+            DiagnosticSeverity.Warning,
+            isEnabledByDefault: true,
+            description: "Make sure to specify the interface in your method-declaration.");
 
         private const string RequiresExplicitImplementationAttributeMetadataName =
             "Robust.Shared.Analyzers.RequiresExplicitImplementationAttribute";

Robust.Analyzers/ExplicitVirtualAnalyzer.cs

@@ -0,0 +1,176 @@
+using System.Collections.Immutable;
+using System.Diagnostics.CodeAnalysis;
+using System.Linq;
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CSharp;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
+using Microsoft.CodeAnalysis.Diagnostics;
+
+namespace Robust.Analyzers;
+
+[DiagnosticAnalyzer(LanguageNames.CSharp)]
+public sealed class ExplicitVirtualAnalyzer : DiagnosticAnalyzer
+{
+    internal const string Attribute = "Robust.Shared.Analyzers.VirtualAttribute";
+
+    [SuppressMessage("ReSharper", "RS2008")]
+    private static readonly DiagnosticDescriptor Rule = new(
+        Diagnostics.IdExplicitVirtual,
+        "Class must be explicitly marked as [Virtual], abstract, static or sealed",
+        "Class must be explicitly marked as [Virtual], abstract, static or sealed",
+        "Usage",
+        DiagnosticSeverity.Warning,
+        isEnabledByDefault: true,
+        description: "Class must be explicitly marked as [Virtual], abstract, static or sealed.");
+
+    public override ImmutableArray<DiagnosticDescriptor> SupportedDiagnostics => ImmutableArray.Create(Rule);
+
+    public override void Initialize(AnalysisContext context)
+    {
+        context.ConfigureGeneratedCodeAnalysis(GeneratedCodeAnalysisFlags.None);
+        context.EnableConcurrentExecution();
+        context.RegisterSyntaxNodeAction(AnalyzeNode, SyntaxKind.ClassDeclaration);
+    }
+
+    private static bool HasAttribute(INamedTypeSymbol namedTypeSymbol, INamedTypeSymbol attrSymbol)
+    {
+        return namedTypeSymbol.GetAttributes()
+            .Any(a => SymbolEqualityComparer.Default.Equals(a.AttributeClass, attrSymbol));
+    }
+
+    private static void AnalyzeNode(SyntaxNodeAnalysisContext context)
+    {
+        var attrSymbol = context.Compilation.GetTypeByMetadataName(Attribute);
+        var classDecl = (ClassDeclarationSyntax)context.Node;
+        var classSymbol = context.SemanticModel.GetDeclaredSymbol(classDecl);
+        if (classSymbol == null)
+            return;
+
+        if (classSymbol.IsSealed || classSymbol.IsAbstract || classSymbol.IsStatic)
+            return;
+
+        if (HasAttribute(classSymbol, attrSymbol))
+            return;
+
+        var diag = Diagnostic.Create(Rule, classDecl.Keyword.GetLocation());
+        context.ReportDiagnostic(diag);
+    }
+}
+
+// Doesn't work as I'd hoped: Roslyn doesn't provide an API for global usings and I can't get batch changes to work.
+/*
+[ExportCodeFixProvider(LanguageNames.CSharp)]
+public sealed class ExplicitVirtualCodeFixProvider : CodeFixProvider
+{
+    private const string TitleSealed = "Annotate class as sealed.";
+    private const string TitleVirtual = "Annotate class as [Virtual].";
+    private const string TitleAbstract = "Annotate class as abstract.";
+    private const string TitleStatic = "Annotate class as static.";
+
+    public override async Task RegisterCodeFixesAsync(CodeFixContext context)
+    {
+        var root = await context.Document.GetSyntaxRootAsync(context.CancellationToken);
+
+        foreach (var diagnostic in context.Diagnostics)
+        {
+            var span = diagnostic.Location.SourceSpan;
+            var classDecl = root.FindToken(span.Start).Parent.AncestorsAndSelf().OfType<ClassDeclarationSyntax>()
+                .First();
+
+            context.RegisterCodeFix(
+                CodeAction.Create(
+                    TitleVirtual,
+                    c => FixVirtualAsync(context.Document, classDecl, c),
+                    TitleVirtual),
+                diagnostic);
+
+            context.RegisterCodeFix(
+                CodeAction.Create(
+                    TitleStatic,
+                    c => FixStaticAsync(context.Document, classDecl, c),
+                    TitleStatic),
+                diagnostic);
+
+            context.RegisterCodeFix(
+                CodeAction.Create(
+                    TitleSealed,
+                    c => FixSealedAsync(context.Document, classDecl, c),
+                    TitleSealed),
+                diagnostic);
+
+            context.RegisterCodeFix(
+                CodeAction.Create(
+                    TitleAbstract,
+                    c => FixAbstractAsync(context.Document, classDecl, c),
+                    TitleAbstract),
+                diagnostic);
+        }
+    }
+
+    private async Task<Document> FixVirtualAsync(
+        Document document,
+        ClassDeclarationSyntax classDecl,
+        CancellationToken cancellationToken)
+    {
+        var ns = "Robust.Shared.Analyzers";
+        var attrib = SyntaxFactory.Attribute(SyntaxFactory.ParseName("Virtual"));
+
+        var newClassDecl = classDecl.AddAttributeLists(
+            SyntaxFactory.AttributeList(SyntaxFactory.SeparatedList(new[] { attrib })));
+
+        var root = (CompilationUnitSyntax)await document.GetSyntaxRootAsync(cancellationToken);
+        root = root.ReplaceNode(classDecl, newClassDecl);
+
+        var options = await document.GetOptionsAsync(cancellationToken);
+
+        if (root.Usings.All(u => u.Name.ToString() != ns))
+        {
+            root = root.AddUsings(SyntaxFactory.UsingDirective(SyntaxFactory.ParseName(ns)));
+        }
+
+        return document.WithSyntaxRoot(root);
+    }
+
+    private async Task<Document> FixStaticAsync(
+        Document document,
+        ClassDeclarationSyntax classDecl,
+        CancellationToken cancellationToken)
+    {
+        var newClassDecl = classDecl.AddModifiers(SyntaxFactory.Token(SyntaxKind.StaticKeyword));
+
+        var root = (CompilationUnitSyntax)await document.GetSyntaxRootAsync(cancellationToken);
+        root = root.ReplaceNode(classDecl, newClassDecl);
+
+        return document.WithSyntaxRoot(root);
+    }
+
+    private async Task<Document> FixAbstractAsync(
+        Document document,
+        ClassDeclarationSyntax classDecl,
+        CancellationToken cancellationToken)
+    {
+        var newClassDecl = classDecl.AddModifiers(SyntaxFactory.Token(SyntaxKind.AbstractKeyword));
+
+        var root = (CompilationUnitSyntax)await document.GetSyntaxRootAsync(cancellationToken);
+        root = root.ReplaceNode(classDecl, newClassDecl);
+
+        return document.WithSyntaxRoot(root);
+    }
+
+    private async Task<Document> FixSealedAsync(
+        Document document,
+        ClassDeclarationSyntax classDecl,
+        CancellationToken cancellationToken)
+    {
+        var newClassDecl = classDecl.AddModifiers(SyntaxFactory.Token(SyntaxKind.SealedKeyword));
+
+        var root = (CompilationUnitSyntax)await document.GetSyntaxRootAsync(cancellationToken);
+        root = root.ReplaceNode(classDecl, newClassDecl);
+
+        return document.WithSyntaxRoot(root);
+    }
+
+    public override FixAllProvider GetFixAllProvider() => WellKnownFixAllProviders.BatchFixer;
+    public override ImmutableArray<string> FixableDiagnosticIds => ImmutableArray.Create(Diagnostics.IdExplicitVirtual);
+}
+*/

Robust.Analyzers/FriendAnalyzer.cs

@@ -14,15 +14,15 @@ namespace Robust.Analyzers
     {
         const string FriendAttribute = "Robust.Shared.Analyzers.FriendAttribute";
 
-        public const string DiagnosticId = "RA0002";
-
-        private const string Title = "Tried to access friend-only member";
-        private const string MessageFormat = "Tried to access member \"{0}\" in class \"{1}\" which can only be accessed by friend classes";
-        private const string Description = "Make sure to specify the accessing class in the friends attribute.";
-        private const string Category = "Usage";
-
         [SuppressMessage("ReSharper", "RS2008")]
-        private static readonly DiagnosticDescriptor Rule = new (DiagnosticId, Title, MessageFormat, Category, DiagnosticSeverity.Error, true, Description);
+        private static readonly DiagnosticDescriptor Rule = new (
+            Diagnostics.IdFriend,
+            "Tried to access friend-only member",
+            "Tried to access member \"{0}\" in class \"{1}\" which can only be accessed by friend classes",
+            "Usage",
+            DiagnosticSeverity.Error,
+            true,
+            "Make sure to specify the accessing class in the friends attribute.");
 
         public override ImmutableArray<DiagnosticDescriptor> SupportedDiagnostics => ImmutableArray.Create(Rule);
 

Robust.Analyzers/MeansImplicitAssigmentSuppressor.cs

@@ -1,9 +1,7 @@
-using System;
 using System.Collections.Immutable;
 using System.Linq;
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.Diagnostics;
-using Robust.Generators;
 
 namespace Robust.Analyzers
 {

Robust.Analyzers/Robust.Analyzers.csproj

@@ -2,7 +2,7 @@
 
   <PropertyGroup>
     <TargetFramework>netstandard2.0</TargetFramework>
-    <LangVersion>9</LangVersion>
+    <LangVersion>10</LangVersion>
   </PropertyGroup>
 
   <ItemGroup>

Robust.Analyzers/SerializableAnalyzer.cs

@@ -17,19 +17,21 @@ namespace Robust.Analyzers
     public class SerializableAnalyzer : DiagnosticAnalyzer
     {
         // Metadata of the analyzer
-        public const string DiagnosticId = "RA0001";
 
         // You could use LocalizedString but it's a little more complicated for this sample
-        private const string Title = "Class not marked as (Net)Serializable";
-        private const string MessageFormat = "Class not marked as (Net)Serializable";
-        private const string Description = "The class should be marked as (Net)Serializable.";
-        private const string Category = "Usage";
 
         private const string RequiresSerializableAttributeMetadataName = "Robust.Shared.Analyzers.RequiresSerializableAttribute";
         private const string SerializableAttributeMetadataName = "System.SerializableAttribute";
         private const string NetSerializableAttributeMetadataName = "Robust.Shared.Serialization.NetSerializableAttribute";
 
-        [SuppressMessage("ReSharper", "RS2008")] private static readonly DiagnosticDescriptor Rule = new DiagnosticDescriptor(DiagnosticId, Title, MessageFormat, Category, DiagnosticSeverity.Warning, isEnabledByDefault: true, description: Description);
+        [SuppressMessage("ReSharper", "RS2008")] private static readonly DiagnosticDescriptor Rule = new(
+            Diagnostics.IdSerializable,
+            "Class not marked as (Net)Serializable",
+            "Class not marked as (Net)Serializable",
+            "Usage",
+            DiagnosticSeverity.Warning,
+            isEnabledByDefault: true,
+            description: "The class should be marked as (Net)Serializable.");
 
         public override ImmutableArray<DiagnosticDescriptor> SupportedDiagnostics => ImmutableArray.Create(Rule);
 
@@ -139,7 +141,8 @@ namespace Robust.Analyzers
             return document.WithSyntaxRoot(root);
         }
 
-        public sealed override ImmutableArray<string> FixableDiagnosticIds => ImmutableArray.Create(SerializableAnalyzer.DiagnosticId);
+        public sealed override ImmutableArray<string> FixableDiagnosticIds
+            => ImmutableArray.Create(Diagnostics.IdSerializable);
 
         public override FixAllProvider GetFixAllProvider()
         {

Robust.Benchmarks/NumericsHelpers/AddBenchmark.cs

@@ -1,7 +1,9 @@
 using BenchmarkDotNet.Attributes;
+using Robust.Shared.Analyzers;
 
 namespace Robust.Benchmarks.NumericsHelpers
 {
+    [Virtual]
     public class AddBenchmark
     {
         [Params(32, 128)]

Robust.Benchmarks/Program.cs

@@ -4,7 +4,7 @@ using System;
 
 namespace Robust.Benchmarks
 {
-    internal class Program
+    internal static class Program
     {
         // --allCategories=ctg1,ctg2
         // --anyCategories=ctg1,ctg2

Robust.Benchmarks/Serialization/BenchmarkIntSerializer.cs

@@ -9,7 +9,7 @@ using Robust.Shared.Serialization.TypeSerializers.Interfaces;
 
 namespace Robust.Benchmarks.Serialization
 {
-    public class BenchmarkIntSerializer : ITypeSerializer<int, ValueDataNode>
+    public sealed class BenchmarkIntSerializer : ITypeSerializer<int, ValueDataNode>
     {
         public ValidationNode Validate(ISerializationManager serializationManager, ValueDataNode node,
             IDependencyCollection dependencies, ISerializationContext? context = null)

Robust.Benchmarks/Serialization/Copy/SerializationCopyBenchmark.cs

@@ -2,6 +2,7 @@
 using System.Linq;
 using BenchmarkDotNet.Attributes;
 using Robust.Benchmarks.Serialization.Definitions;
+using Robust.Shared.Analyzers;
 using Robust.Shared.Serialization.Manager;
 using Robust.Shared.Serialization.Markdown;
 using Robust.Shared.Serialization.Markdown.Mapping;
@@ -13,6 +14,7 @@ using YamlDotNet.RepresentationModel;
 namespace Robust.Benchmarks.Serialization.Copy
 {
     [MemoryDiagnoser]
+    [Virtual]
     public class SerializationCopyBenchmark : SerializationBenchmark
     {
         public SerializationCopyBenchmark()

Robust.Benchmarks/Serialization/Definitions/BenchmarkFlags.cs

@@ -3,7 +3,7 @@ using Robust.Shared.Serialization;
 
 namespace Robust.Benchmarks.Serialization.Definitions
 {
-    public class BenchmarkFlags
+    public sealed class BenchmarkFlags
     {
         public const int Zero = 1 << 0;
         public const int ThirtyOne = 1 << 31;

Robust.Benchmarks/Serialization/Definitions/DataDefinitionWithString.cs

@@ -1,8 +1,10 @@
-using Robust.Shared.Serialization.Manager.Attributes;
+using Robust.Shared.Analyzers;
+using Robust.Shared.Serialization.Manager.Attributes;
 
 namespace Robust.Benchmarks.Serialization.Definitions
 {
     [DataDefinition]
+    [Virtual]
     public class DataDefinitionWithString
     {
         [DataField("string")]

Robust.Benchmarks/Serialization/Definitions/SeedDataDefinition.cs

@@ -11,7 +11,7 @@ namespace Robust.Benchmarks.Serialization.Definitions
     ///     Taken from content.
     /// </summary>
     [Prototype("seed")]
-    public class SeedDataDefinition : IPrototype
+    public sealed class SeedDataDefinition : IPrototype
     {
         public const string Prototype = @"
 - type: seed

Robust.Benchmarks/Serialization/Initialize/SerializationInitializeBenchmark.cs

@@ -1,9 +1,11 @@
 using BenchmarkDotNet.Attributes;
+using Robust.Shared.Analyzers;
 using Robust.Shared.Serialization.Manager;
 
 namespace Robust.Benchmarks.Serialization.Initialize
 {
     [MemoryDiagnoser]
+    [Virtual]
     public class SerializationInitializeBenchmark : SerializationBenchmark
     {
         [IterationCleanup]

Robust.Benchmarks/Serialization/Read/SerializationReadBenchmark.cs

@@ -1,6 +1,7 @@
 using System.IO;
 using BenchmarkDotNet.Attributes;
 using Robust.Benchmarks.Serialization.Definitions;
+using Robust.Shared.Analyzers;
 using Robust.Shared.Serialization.Manager.Result;
 using Robust.Shared.Serialization.Markdown;
 using Robust.Shared.Serialization.Markdown.Mapping;
@@ -12,6 +13,7 @@ using YamlDotNet.RepresentationModel;
 namespace Robust.Benchmarks.Serialization.Read
 {
     [MemoryDiagnoser]
+    [Virtual]
     public class SerializationReadBenchmark : SerializationBenchmark
     {
         public SerializationReadBenchmark()

Robust.Benchmarks/Serialization/SerializationArrayBenchmark.cs

@@ -1,5 +1,6 @@
 using BenchmarkDotNet.Attributes;
 using Robust.Benchmarks.Serialization.Definitions;
+using Robust.Shared.Analyzers;
 using Robust.Shared.Serialization.Markdown.Mapping;
 using Robust.Shared.Serialization.Markdown.Sequence;
 using Robust.Shared.Serialization.Markdown.Value;
@@ -7,6 +8,7 @@ using Robust.Shared.Serialization.Markdown.Value;
 namespace Robust.Benchmarks.Serialization
 {
     [MemoryDiagnoser]
+    [Virtual]
     public class SerializationArrayBenchmark : SerializationBenchmark
     {
         public SerializationArrayBenchmark()

Robust.Benchmarks/Serialization/Write/SerializationWriteBenchmark.cs

@@ -2,6 +2,7 @@
 using System.IO;
 using BenchmarkDotNet.Attributes;
 using Robust.Benchmarks.Serialization.Definitions;
+using Robust.Shared.Analyzers;
 using Robust.Shared.Serialization.Manager;
 using Robust.Shared.Serialization.Markdown;
 using Robust.Shared.Serialization.Markdown.Mapping;
@@ -13,6 +14,7 @@ using YamlDotNet.RepresentationModel;
 namespace Robust.Benchmarks.Serialization.Write
 {
     [MemoryDiagnoser]
+    [Virtual]
     public class SerializationWriteBenchmark : SerializationBenchmark
     {
         public SerializationWriteBenchmark()

Robust.Client/Animations/AnimationTrackControlProperty.cs

@@ -3,7 +3,7 @@ using Robust.Shared.Animations;
 
 namespace Robust.Client.Animations
 {
-    public class AnimationTrackControlProperty : AnimationTrackProperty
+    public sealed class AnimationTrackControlProperty : AnimationTrackProperty
     {
         public string? Property { get; set; }
 

Robust.Client/Audio/Midi/MidiManager.cs

@@ -58,7 +58,7 @@ namespace Robust.Client.Audio.Midi
         void Shutdown();
     }
 
-    internal class MidiManager : IMidiManager
+    internal sealed class MidiManager : IMidiManager
     {
         [Dependency] private readonly IEyeManager _eyeManager = default!;
         [Dependency] private readonly IResourceManagerInternal _resourceManager = default!;
@@ -392,7 +392,7 @@ namespace Robust.Client.Audio.Midi
         /// <summary>
         ///     This class is used to load soundfonts.
         /// </summary>
-        private class ResourceLoaderCallbacks : SoundFontLoaderCallbacks
+        private sealed class ResourceLoaderCallbacks : SoundFontLoaderCallbacks
         {
             private readonly Dictionary<int, Stream> _openStreams = new();
             private int _nextStreamId = 1;

Robust.Client/Audio/Midi/MidiRenderer.cs

@@ -180,7 +180,7 @@ namespace Robust.Client.Audio.Midi
         internal void InternalDispose();
     }
 
-    internal class MidiRenderer : IMidiRenderer
+    internal sealed class MidiRenderer : IMidiRenderer
     {
         [Dependency] private readonly IClydeAudio _clydeAudio = default!;
         [Dependency] private readonly ITaskManager _taskManager = default!;

Robust.Client/BaseClient.cs

@@ -20,13 +20,12 @@ using Robust.Shared.Utility;
 namespace Robust.Client
 {
     /// <inheritdoc />
-    public class BaseClient : IBaseClient
+    public sealed class BaseClient : IBaseClient
     {
         [Dependency] private readonly IClientNetManager _net = default!;
         [Dependency] private readonly IPlayerManager _playMan = default!;
         [Dependency] private readonly INetConfigurationManager _configManager = default!;
         [Dependency] private readonly IClientEntityManager _entityManager = default!;
-        [Dependency] private readonly IEntityLookup _entityLookup = default!;
         [Dependency] private readonly IMapManager _mapManager = default!;
         [Dependency] private readonly IDiscordRichPresence _discord = default!;
         [Dependency] private readonly IGameTiming _timing = default!;
@@ -213,7 +212,6 @@ namespace Robust.Client
         {
             _entityManager.Startup();
             _mapManager.Startup();
-            _entityLookup.Startup();
 
             _timing.ResetSimTime();
             _timing.Paused = false;
@@ -224,7 +222,6 @@ namespace Robust.Client
             IoCManager.Resolve<INetConfigurationManager>().FlushMessages();
             _gameStates.Reset();
             _playMan.Shutdown();
-            _entityLookup.Shutdown();
             _entityManager.Shutdown();
             _mapManager.Shutdown();
             _discord.ClearPresence();
@@ -291,7 +288,7 @@ namespace Robust.Client
     /// <summary>
     ///     Event arguments for when something changed with the player.
     /// </summary>
-    public class PlayerEventArgs : EventArgs
+    public sealed class PlayerEventArgs : EventArgs
     {
         /// <summary>
         ///     The session that triggered the event.
@@ -310,7 +307,7 @@ namespace Robust.Client
     /// <summary>
     ///     Event arguments for when the RunLevel has changed in the BaseClient.
     /// </summary>
-    public class RunLevelChangedEventArgs : EventArgs
+    public sealed class RunLevelChangedEventArgs : EventArgs
     {
         /// <summary>
         ///     RunLevel that the BaseClient switched from.
@@ -335,7 +332,7 @@ namespace Robust.Client
     /// <summary>
     ///     Info about the server and player that is sent to the client while connecting.
     /// </summary>
-    public class ServerInfo
+    public sealed class ServerInfo
     {
         public ServerInfo(string serverName)
         {

Robust.Client/ClientIoC.cs

@@ -43,11 +43,10 @@ namespace Robust.Client
             IoCManager.Register<IGameTiming, ClientGameTiming>();
             IoCManager.Register<IClientGameTiming, ClientGameTiming>();
             IoCManager.Register<IPrototypeManager, ClientPrototypeManager>();
-            IoCManager.Register<IMapManager, ClientMapManager>();
-            IoCManager.Register<IMapManagerInternal, ClientMapManager>();
-            IoCManager.Register<IClientMapManager, ClientMapManager>();
+            IoCManager.Register<IMapManager, NetworkedMapManager>();
+            IoCManager.Register<IMapManagerInternal, NetworkedMapManager>();
+            IoCManager.Register<INetworkedMapManager, NetworkedMapManager>();
             IoCManager.Register<IEntityManager, ClientEntityManager>();
-            IoCManager.Register<IEntityLookup, EntityLookup>();
             IoCManager.Register<IReflectionManager, ClientReflectionManager>();
             IoCManager.Register<IConsoleHost, ClientConsoleHost>();
             IoCManager.Register<IClientConsoleHost, ClientConsoleHost>();
@@ -72,7 +71,6 @@ namespace Robust.Client
             IoCManager.Register<IStateManager, StateManager>();
             IoCManager.Register<IUserInterfaceManager, UserInterfaceManager>();
             IoCManager.Register<IUserInterfaceManagerInternal, UserInterfaceManager>();
-            IoCManager.Register<IDebugDrawing, DebugDrawing>();
             IoCManager.Register<ILightManager, LightManager>();
             IoCManager.Register<IDiscordRichPresence, DiscordRichPresence>();
             IoCManager.Register<IMidiManager, MidiManager>();

Robust.Client/Console/ClientConGroupController.cs

@@ -2,7 +2,7 @@
 
 namespace Robust.Client.Console
 {
-    public class ClientConGroupController : IClientConGroupController
+    public sealed class ClientConGroupController : IClientConGroupController
     {
         private IClientConGroupImplementation? _implementation;
         public event Action? ConGroupUpdated;

Robust.Client/Console/ClientConsoleHost.cs

@@ -14,7 +14,7 @@ using Robust.Shared.Utility;
 
 namespace Robust.Client.Console
 {
-    public class AddStringArgs : EventArgs
+    public sealed class AddStringArgs : EventArgs
     {
         public string Text { get; }
 
@@ -30,7 +30,7 @@ namespace Robust.Client.Console
         }
     }
 
-    public class AddFormattedMessageArgs : EventArgs
+    public sealed class AddFormattedMessageArgs : EventArgs
     {
         public readonly FormattedMessage Message;
 
@@ -41,7 +41,7 @@ namespace Robust.Client.Console
     }
 
     /// <inheritdoc cref="IClientConsoleHost" />
-    internal class ClientConsoleHost : ConsoleHost, IClientConsoleHost
+    internal sealed class ClientConsoleHost : ConsoleHost, IClientConsoleHost
     {
         [Dependency] private readonly IClientConGroupController _conGroup = default!;
 
@@ -109,13 +109,13 @@ namespace Robust.Client.Console
             if (AvailableCommands.ContainsKey(commandName))
             {
                 var playerManager = IoCManager.Resolve<IPlayerManager>();
-
+#if !DEBUG
                 if (!_conGroup.CanCommand(commandName) && playerManager.LocalPlayer?.Session.Status > SessionStatus.Connecting)
                 {
                     WriteError(null, $"Insufficient perms for command: {commandName}");
                     return;
                 }
-
+#endif
                 var command1 = AvailableCommands[commandName];
                 args.RemoveAt(0);
                 var shell = new ConsoleShell(this, null);
@@ -209,7 +209,7 @@ namespace Robust.Client.Console
     /// These dummies are made purely so list and help can list server-side commands.
     /// </summary>
     [Reflect(false)]
-    internal class ServerDummyCommand : IConsoleCommand
+    internal sealed class ServerDummyCommand : IConsoleCommand
     {
         internal ServerDummyCommand(string command, string help, string description)
         {

Robust.Client/Console/Commands/ConfigurationCommands.cs

@@ -59,7 +59,7 @@ namespace Robust.Client.Console.Commands
     }
 
     [UsedImplicitly]
-    public class SaveConfig : IConsoleCommand
+    public sealed class SaveConfig : IConsoleCommand
     {
         public string Command => "saveconfig";
         public string Description => "Saves the client configuration to the config file";

Robust.Client/Console/Commands/ConsoleCommands.cs

@@ -6,7 +6,7 @@ using Robust.Shared.Console;
 
 namespace Robust.Client.Console.Commands
 {
-    class ClearCommand : IConsoleCommand
+    sealed class ClearCommand : IConsoleCommand
     {
         public string Command => "cls";
         public string Help => "Clears the debug console of all messages.";
@@ -18,7 +18,7 @@ namespace Robust.Client.Console.Commands
         }
     }
 
-    class FillCommand : IConsoleCommand
+    sealed class FillCommand : IConsoleCommand
     {
         public string Command => "fill";
         public string Help => "Fills the console with some nonsense for debugging.";

Robust.Client/Console/Commands/Debug.cs

@@ -30,7 +30,7 @@ using static Robust.Client.UserInterface.Controls.BoxContainer;
 
 namespace Robust.Client.Console.Commands
 {
-    internal class DumpEntitiesCommand : IConsoleCommand
+    internal sealed class DumpEntitiesCommand : IConsoleCommand
     {
         public string Command => "dumpentities";
         public string Help => "Dump entity list";
@@ -47,7 +47,7 @@ namespace Robust.Client.Console.Commands
         }
     }
 
-    internal class GetComponentRegistrationCommand : IConsoleCommand
+    internal sealed class GetComponentRegistrationCommand : IConsoleCommand
     {
         public string Command => "getcomponentregistration";
         public string Help => "Usage: getcomponentregistration <componentName>";
@@ -93,7 +93,7 @@ namespace Robust.Client.Console.Commands
         }
     }
 
-    internal class ToggleMonitorCommand : IConsoleCommand
+    internal sealed class ToggleMonitorCommand : IConsoleCommand
     {
         public string Command => "monitor";
 
@@ -148,7 +148,7 @@ namespace Robust.Client.Console.Commands
         }
     }
 
-    internal class ExceptionCommand : IConsoleCommand
+    internal sealed class ExceptionCommand : IConsoleCommand
     {
         public string Command => "fuck";
         public string Help => "Throws an exception";
@@ -160,7 +160,7 @@ namespace Robust.Client.Console.Commands
         }
     }
 
-    internal class ShowPositionsCommand : IConsoleCommand
+    internal sealed class ShowPositionsCommand : IConsoleCommand
     {
         public string Command => "showpos";
         public string Help => "";
@@ -168,12 +168,12 @@ namespace Robust.Client.Console.Commands
 
         public void Execute(IConsoleShell shell, string argStr, string[] args)
         {
-            var mgr = IoCManager.Resolve<IDebugDrawing>();
+            var mgr = EntitySystem.Get<DebugDrawingSystem>();
             mgr.DebugPositions = !mgr.DebugPositions;
         }
     }
 
-    internal class ShowRayCommand : IConsoleCommand
+    internal sealed class ShowRayCommand : IConsoleCommand
     {
         public string Command => "showrays";
         public string Help => "Usage: showrays <raylifetime>";
@@ -200,7 +200,7 @@ namespace Robust.Client.Console.Commands
         }
     }
 
-    internal class DisconnectCommand : IConsoleCommand
+    internal sealed class DisconnectCommand : IConsoleCommand
     {
         public string Command => "disconnect";
         public string Help => "";
@@ -212,7 +212,7 @@ namespace Robust.Client.Console.Commands
         }
     }
 
-    internal class EntityInfoCommand : IConsoleCommand
+    internal sealed class EntityInfoCommand : IConsoleCommand
     {
         public string Command => "entfo";
 
@@ -264,7 +264,7 @@ namespace Robust.Client.Console.Commands
         }
     }
 
-    internal class SnapGridGetCell : IConsoleCommand
+    internal sealed class SnapGridGetCell : IConsoleCommand
     {
         public string Command => "sggcell";
         public string Help => "sggcell <gridID> <vector2i>\nThat vector2i param is in the form x<int>,y<int>.";
@@ -313,7 +313,7 @@ namespace Robust.Client.Console.Commands
         }
     }
 
-    internal class SetPlayerName : IConsoleCommand
+    internal sealed class SetPlayerName : IConsoleCommand
     {
         public string Command => "overrideplayername";
         public string Description => "Changes the name used when attempting to connect to the server.";
@@ -333,7 +333,7 @@ namespace Robust.Client.Console.Commands
         }
     }
 
-    internal class LoadResource : IConsoleCommand
+    internal sealed class LoadResource : IConsoleCommand
     {
         public string Command => "ldrsc";
         public string Description => "Pre-caches a resource.";
@@ -370,7 +370,7 @@ namespace Robust.Client.Console.Commands
         }
     }
 
-    internal class ReloadResource : IConsoleCommand
+    internal sealed class ReloadResource : IConsoleCommand
     {
         public string Command => "rldrsc";
         public string Description => "Reloads a resource.";
@@ -404,7 +404,7 @@ namespace Robust.Client.Console.Commands
         }
     }
 
-    internal class GridTileCount : IConsoleCommand
+    internal sealed class GridTileCount : IConsoleCommand
     {
         public string Command => "gridtc";
         public string Description => "Gets the tile count of a grid";
@@ -438,7 +438,7 @@ namespace Robust.Client.Console.Commands
         }
     }
 
-    internal class GuiDumpCommand : IConsoleCommand
+    internal sealed class GuiDumpCommand : IConsoleCommand
     {
         public string Command => "guidump";
         public string Description => "Dump GUI tree to /guidump.txt in user data.";
@@ -512,7 +512,7 @@ namespace Robust.Client.Console.Commands
         }
     }
 
-    internal class UITestCommand : IConsoleCommand
+    internal sealed class UITestCommand : IConsoleCommand
     {
         public string Command => "uitest";
         public string Description => "Open a dummy UI testing window";
@@ -644,7 +644,7 @@ namespace Robust.Client.Console.Commands
         }
     }
 
-    internal class SetClipboardCommand : IConsoleCommand
+    internal sealed class SetClipboardCommand : IConsoleCommand
     {
         public string Command => "setclipboard";
         public string Description => "Sets the system clipboard";
@@ -657,7 +657,7 @@ namespace Robust.Client.Console.Commands
         }
     }
 
-    internal class GetClipboardCommand : IConsoleCommand
+    internal sealed class GetClipboardCommand : IConsoleCommand
     {
         public string Command => "getclipboard";
         public string Description => "Gets the system clipboard";
@@ -670,7 +670,7 @@ namespace Robust.Client.Console.Commands
         }
     }
 
-    internal class ToggleLight : IConsoleCommand
+    internal sealed class ToggleLight : IConsoleCommand
     {
         public string Command => "togglelight";
         public string Description => "Toggles light rendering.";
@@ -684,7 +684,7 @@ namespace Robust.Client.Console.Commands
         }
     }
 
-    internal class ToggleFOV : IConsoleCommand
+    internal sealed class ToggleFOV : IConsoleCommand
     {
         public string Command => "togglefov";
         public string Description => "Toggles fov for client.";
@@ -698,7 +698,7 @@ namespace Robust.Client.Console.Commands
         }
     }
 
-    internal class ToggleHardFOV : IConsoleCommand
+    internal sealed class ToggleHardFOV : IConsoleCommand
     {
         public string Command => "togglehardfov";
         public string Description => "Toggles hard fov for client (for debugging space-station-14#2353).";
@@ -712,7 +712,7 @@ namespace Robust.Client.Console.Commands
         }
     }
 
-    internal class ToggleShadows : IConsoleCommand
+    internal sealed class ToggleShadows : IConsoleCommand
     {
         public string Command => "toggleshadows";
         public string Description => "Toggles shadow rendering.";
@@ -725,7 +725,7 @@ namespace Robust.Client.Console.Commands
                 mgr.DrawShadows = !mgr.DrawShadows;
         }
     }
-    internal class ToggleLightBuf : IConsoleCommand
+    internal sealed class ToggleLightBuf : IConsoleCommand
     {
         public string Command => "togglelightbuf";
         public string Description => "Toggles lighting rendering. This includes shadows but not FOV.";
@@ -739,7 +739,7 @@ namespace Robust.Client.Console.Commands
         }
     }
 
-    internal class GcCommand : IConsoleCommand
+    internal sealed class GcCommand : IConsoleCommand
     {
         public string Command => "gc";
         public string Description => "Run the GC.";
@@ -761,7 +761,7 @@ namespace Robust.Client.Console.Commands
         }
     }
 
-    internal class GcFullCommand : IConsoleCommand
+    internal sealed class GcFullCommand : IConsoleCommand
     {
         public string Command => "gcf";
         public string Description => "Run the GC, fully, compacting LOH and everything.";
@@ -774,7 +774,7 @@ namespace Robust.Client.Console.Commands
         }
     }
 
-    internal class GcModeCommand : IConsoleCommand
+    internal sealed class GcModeCommand : IConsoleCommand
     {
 
         public string Command => "gc_mode";
@@ -816,7 +816,7 @@ namespace Robust.Client.Console.Commands
 
     }
 
-    internal class SerializeStatsCommand : IConsoleCommand
+    internal sealed class SerializeStatsCommand : IConsoleCommand
     {
 
         public string Command => "szr_stats";
@@ -836,7 +836,7 @@ namespace Robust.Client.Console.Commands
 
     }
 
-    internal class ChunkInfoCommand : IConsoleCommand
+    internal sealed class ChunkInfoCommand : IConsoleCommand
     {
         public string Command => "chunkinfo";
         public string Description => "Gets info about a chunk under your mouse cursor.";
@@ -861,11 +861,11 @@ namespace Robust.Client.Console.Commands
             var chunkIndex = grid.LocalToChunkIndices(grid.MapToGrid(mousePos));
             var chunk = internalGrid.GetChunk(chunkIndex);
 
-            shell.WriteLine($"worldBounds: {chunk.CalcWorldAABB()} localBounds: {chunk.CalcLocalBounds()}");
+            shell.WriteLine($"worldBounds: {internalGrid.CalcWorldAABB(chunk)} localBounds: {chunk.CachedBounds}");
         }
     }
 
-    internal class ReloadShadersCommand : IConsoleCommand
+    internal sealed class ReloadShadersCommand : IConsoleCommand
     {
 
         public string Command => "rldshader";
@@ -1036,7 +1036,7 @@ namespace Robust.Client.Console.Commands
 
     }
 
-    internal class ClydeDebugLayerCommand : IConsoleCommand
+    internal sealed class ClydeDebugLayerCommand : IConsoleCommand
     {
         public string Command => "cldbglyr";
         public string Description => "Toggle fov and light debug layers";
@@ -1061,7 +1061,7 @@ namespace Robust.Client.Console.Commands
         }
     }
 
-    internal class GetKeyInfoCommand : IConsoleCommand
+    internal sealed class GetKeyInfoCommand : IConsoleCommand
     {
         public string Command => "keyinfo";
         public string Description => "Keys key info for a key";

Robust.Client/Console/Commands/GridChunkBBCommand.cs

@@ -4,7 +4,7 @@ using Robust.Shared.GameObjects;
 
 namespace Robust.Client.Console.Commands
 {
-    public class GridChunkBBCommand : IConsoleCommand
+    public sealed class GridChunkBBCommand : IConsoleCommand
     {
         public string Command => "showchunkbb";
         public string Description => "Displays chunk bounds for the purposes of rendering";

Robust.Client/Console/Commands/HelpCommands.cs

@@ -5,7 +5,7 @@ using Robust.Shared.Network;
 
 namespace Robust.Client.Console.Commands
 {
-    class HelpCommand : IConsoleCommand
+    sealed class HelpCommand : IConsoleCommand
     {
         public string Command => "help";
         public string Help => "When no arguments are provided, displays a generic help text. When an argument is passed, display the help text for the command with that name.";
@@ -44,7 +44,7 @@ namespace Robust.Client.Console.Commands
         }
     }
 
-    class ListCommand : IConsoleCommand
+    sealed class ListCommand : IConsoleCommand
     {
         public string Command => "list";
         public string Help => "Usage: list [filter]\n" +

Robust.Client/Console/Commands/LogCommands.cs

@@ -4,7 +4,7 @@ using Robust.Shared.Console;
 
 namespace Robust.Client.Console.Commands
 {
-    class LogSetLevelCommand : IConsoleCommand
+    sealed class LogSetLevelCommand : IConsoleCommand
     {
         public string Command => "loglevel";
         public string Description => "Changes the log level for a provided sawmill.";
@@ -40,7 +40,7 @@ namespace Robust.Client.Console.Commands
         }
     }
 
-    class TestLog : IConsoleCommand
+    sealed class TestLog : IConsoleCommand
     {
         public string Command => "testlog";
         public string Description => "Writes a test log to a sawmill.";

Robust.Client/Console/Commands/QuitCommand.cs

@@ -4,7 +4,7 @@ using Robust.Shared.IoC;
 
 namespace Robust.Client.Console.Commands
 {
-    class HardQuitCommand : IConsoleCommand
+    sealed class HardQuitCommand : IConsoleCommand
     {
         public string Command => "hardquit";
         public string Description => "Kills the game client instantly.";
@@ -16,7 +16,7 @@ namespace Robust.Client.Console.Commands
         }
     }
 
-    class QuitCommand : IConsoleCommand
+    sealed class QuitCommand : IConsoleCommand
     {
         public string Command => "quit";
         public string Description => "Shuts down the game client gracefully.";

Robust.Client/Console/Commands/SetInputContextCommand.cs

@@ -6,7 +6,7 @@ using Robust.Shared.IoC;
 namespace Robust.Client.Console.Commands
 {
     [UsedImplicitly]
-    public class SetInputContextCommand : IConsoleCommand
+    public sealed class SetInputContextCommand : IConsoleCommand
     {
         public string Command => "setinputcontext";
         public string Description => "Sets the active input context.";

Robust.Client/Console/Commands/VelocitiesCommand.cs

@@ -4,7 +4,7 @@ using Robust.Shared.GameObjects;
 
 namespace Robust.Client.Console.Commands
 {
-    public class VelocitiesCommand : IConsoleCommand
+    public sealed class VelocitiesCommand : IConsoleCommand
     {
         public string Command => "showvelocities";
         public string Description => "Displays your angular and linear velocities";

Robust.Client/Console/Completions.cs

@@ -11,7 +11,7 @@ using static Robust.Shared.Network.Messages.MsgScriptCompletionResponse;
 
 namespace Robust.Client.Console
 {
-    public class Completions : DefaultWindow
+    public sealed class Completions : DefaultWindow
     {
         private HistoryLineEdit _textBar;
         private ScrollContainer _suggestPanel = new()
@@ -75,7 +75,7 @@ namespace Robust.Client.Console
         }
 
         // Label and ghetto button.
-        public class Entry : RichTextLabel
+        public sealed class Entry : RichTextLabel
         {
             public readonly LiteResult Result;
 

Robust.Client/Console/ScriptClient.cs

@@ -6,7 +6,7 @@ using Robust.Shared.Network.Messages;
 
 namespace Robust.Client.Console
 {
-    public partial class ScriptClient : IScriptClient
+    public sealed partial class ScriptClient : IScriptClient
     {
         [Dependency] private readonly IClientConGroupController _conGroupController = default!;
         [Dependency] private readonly IClientNetManager _netManager = default!;

Robust.Client/Console/WatchWindow.cs

@@ -15,7 +15,7 @@ using static Robust.Client.UserInterface.Controls.BoxContainer;
 
 namespace Robust.Client.Console
 {
-    public class WatchWindow : DefaultWindow
+    public sealed class WatchWindow : DefaultWindow
     {
         private readonly IReflectionManager _reflectionManager;
 

Robust.Client/Debugging/DebugDrawingSystem.cs

@@ -6,17 +6,21 @@ using Robust.Shared.Maths;
 
 namespace Robust.Client.Debugging
 {
-    /// <inheritdoc />
-    public class DebugDrawing : IDebugDrawing
+    /// <summary>
+    /// A collection of visual debug overlays for the client game.
+    /// </summary>
+    public sealed class DebugDrawingSystem : EntitySystem
     {
         [Dependency] private readonly IOverlayManager _overlayManager = default!;
         [Dependency] private readonly IEyeManager _eyeManager = default!;
-        [Dependency] private readonly IEntityLookup _lookup = default!;
         [Dependency] private readonly IEntityManager _entityManager = default!;
+        [Dependency] private readonly EntityLookupSystem _lookup = default!;
 
         private bool _debugPositions;
 
-        /// <inheritdoc />
+        /// <summary>
+        /// Toggles the visual overlay of the local origin for each entity on screen.
+        /// </summary>
         public bool DebugPositions
         {
             get => _debugPositions;
@@ -42,13 +46,13 @@ namespace Robust.Client.Debugging
 
         private sealed class EntityPositionOverlay : Overlay
         {
-            private readonly IEntityLookup _lookup;
+            private readonly EntityLookupSystem _lookup;
             private readonly IEyeManager _eyeManager;
             private readonly IEntityManager _entityManager;
 
             public override OverlaySpace Space => OverlaySpace.WorldSpace;
 
-            public EntityPositionOverlay(IEntityLookup lookup, IEyeManager eyeManager, IEntityManager entityManager)
+            public EntityPositionOverlay(EntityLookupSystem lookup, IEyeManager eyeManager, IEntityManager entityManager)
             {
                 _lookup = lookup;
                 _eyeManager = eyeManager;
@@ -61,13 +65,11 @@ namespace Robust.Client.Debugging
 
                 var worldHandle = (DrawingHandleWorld) args.DrawingHandle;
                 var viewport = _eyeManager.GetWorldViewport();
+                var xformQuery = _entityManager.GetEntityQuery<TransformComponent>();
 
                 foreach (var entity in _lookup.GetEntitiesIntersecting(_eyeManager.CurrentMap, viewport))
                 {
-                    var transform = _entityManager.GetComponent<TransformComponent>(entity);
-
-                    var center = transform.WorldPosition;
-                    var worldRotation = transform.WorldRotation;
+                    var (center, worldRotation) = xformQuery.GetComponent(entity).GetWorldPositionRotation();
 
                     var xLine = worldRotation.RotateVec(Vector2.UnitX);
                     var yLine = worldRotation.RotateVec(Vector2.UnitY);

Robust.Client/Debugging/DebugPhysicsSystem.cs

@@ -209,8 +209,8 @@ namespace Robust.Client.Debugging
 
                     foreach (var fixture in _entityManager.GetComponent<FixturesComponent>(physBody.Owner).Fixtures.Values)
                     {
-                        // Invalid shape - Box2D doesn't check for IsSensor
-                        if (physBody.BodyType == BodyType.Dynamic && fixture.Mass == 0f)
+                        // Invalid shape - Box2D doesn't check for IsSensor but we will for sanity.
+                        if (physBody.BodyType == BodyType.Dynamic && fixture.Mass == 0f && fixture.Hard)
                         {
                             DrawShape(worldHandle, fixture, xform, Color.Red.WithAlpha(AlphaModifier));
                         }

Robust.Client/Debugging/IDebugDrawing.cs

@@ -1,13 +0,0 @@
-namespace Robust.Client.Debugging
-{
-    /// <summary>
-    /// A collection of visual debug overlays for the client game.
-    /// </summary>
-    public interface IDebugDrawing
-    {
-        /// <summary>
-        /// Toggles the visual overlay of the local origin for each entity on screen.
-        /// </summary>
-        bool DebugPositions { get; set; }
-    }
-}

Robust.Client/GameController/GameController.Loader.cs

@@ -7,7 +7,7 @@ namespace Robust.Client
 {
     internal partial class GameController
     {
-        internal class LoaderEntryPoint : ILoaderEntryPoint
+        internal sealed class LoaderEntryPoint : ILoaderEntryPoint
         {
             public void Main(IMainArgs args)
             {

Robust.Client/GameController/GameController.cs

@@ -50,7 +50,6 @@ namespace Robust.Client
         [Dependency] private readonly IClientConsoleHost _console = default!;
         [Dependency] private readonly ITimerManager _timerManager = default!;
         [Dependency] private readonly IClientEntityManager _entityManager = default!;
-        [Dependency] private readonly IEntityLookup _lookup = default!;
         [Dependency] private readonly IPlacementManager _placementManager = default!;
         [Dependency] private readonly IClientGameStateManager _gameStateManager = default!;
         [Dependency] private readonly IOverlayManagerInternal _overlayManager = default!;
@@ -455,6 +454,7 @@ namespace Robust.Client
         private void Tick(FrameEventArgs frameEventArgs)
         {
             _modLoader.BroadcastUpdate(ModUpdateLevel.PreEngine, frameEventArgs);
+            _console.CommandBufferExecute();
             _timerManager.UpdateTimers(frameEventArgs);
             _taskManager.ProcessPendingTasks();
 
@@ -470,7 +470,6 @@ namespace Robust.Client
                 // The last real tick is the current tick! This way we won't be in "prediction" mode.
                 _gameTiming.LastRealTick = _gameTiming.CurTick;
                 _entityManager.TickUpdate(frameEventArgs.DeltaSeconds, noPredictions: false);
-                _lookup.Update();
             }
 
             _modLoader.BroadcastUpdate(ModUpdateLevel.PostEngine, frameEventArgs);
@@ -510,7 +509,7 @@ namespace Robust.Client
             logManager.GetSawmill("discord").Level = LogLevel.Warning;
             logManager.GetSawmill("net.predict").Level = LogLevel.Info;
             logManager.GetSawmill("szr").Level = LogLevel.Info;
-            logManager.GetSawmill("loc").Level = LogLevel.Error;
+            logManager.GetSawmill("loc").Level = LogLevel.Warning;
 
 #if DEBUG_ONLY_FCE_INFO
 #if DEBUG_ONLY_FCE_LOG
@@ -575,7 +574,6 @@ namespace Robust.Client
 
             _networkManager.Shutdown("Client shutting down");
             _midiManager.Shutdown();
-            IoCManager.Resolve<IEntityLookup>().Shutdown();
             _entityManager.Shutdown();
             _clyde.Shutdown();
             _clydeAudio.Shutdown();

Robust.Client/GameControllerOptions.cs

@@ -3,7 +3,7 @@ using Robust.Shared.Utility;
 
 namespace Robust.Client
 {
-    public class GameControllerOptions
+    public sealed class GameControllerOptions
     {
         /// <summary>
         ///     Whether content sandboxing will be enabled & enforced.

Robust.Client/GameObjects/ClientComponentFactory.cs

@@ -6,7 +6,7 @@ using Robust.Shared.Reflection;
 
 namespace Robust.Client.GameObjects
 {
-    internal class ClientComponentFactory : ComponentFactory
+    internal sealed class ClientComponentFactory : ComponentFactory
     {
         public ClientComponentFactory(IDynamicTypeFactoryInternal typeFactory, IReflectionManager reflectionManager, IConsoleHost conHost)
             : base(typeFactory, reflectionManager, conHost)

Robust.Client/GameObjects/ComponentStateApplyException.cs

@@ -4,6 +4,7 @@ using System.Runtime.Serialization;
 namespace Robust.Client.GameObjects
 {
     [Serializable]
+    [Virtual]
     public class ComponentStateApplyException : Exception
     {
         public ComponentStateApplyException()

Robust.Client/GameObjects/Components/Appearance/AppearanceVisualizer.cs

@@ -1,4 +1,5 @@
-using Robust.Shared.GameObjects;
+using System;
+using Robust.Shared.GameObjects;
 using Robust.Shared.Serialization.Manager.Attributes;
 
 namespace Robust.Client.GameObjects;
@@ -14,6 +15,7 @@ public abstract class AppearanceVisualizer
     ///     Initializes an entity to be managed by this appearance controller.
     ///     DO NOT assume this is your only entity. Visualizers are shared.
     /// </summary>
+    [Obsolete("Subscribe to your component being initialised instead.")]
     public virtual void InitializeEntity(EntityUid entity)
     {
     }
@@ -23,6 +25,7 @@ public abstract class AppearanceVisualizer
     ///     Update its visuals here.
     /// </summary>
     /// <param name="component">The appearance component of the entity that might need updating.</param>
+    [Obsolete("Subscribe to AppearanceChangeEvent instead.")]
     public virtual void OnChangeData(AppearanceComponent component)
     {
     }

Robust.Client/GameObjects/Components/Appearance/ClientAppearanceComponent.cs

@@ -1,4 +1,5 @@
 using System.Collections.Generic;
+using Robust.Shared.Analyzers;
 using Robust.Shared.GameObjects;
 using Robust.Shared.Serialization.Manager.Attributes;
 using Robust.Shared.ViewVariables;
@@ -9,39 +10,10 @@ namespace Robust.Client.GameObjects;
 /// This is the client instance of <see cref="AppearanceComponent"/>.
 /// </summary>
 [RegisterComponent]
-[ComponentReference(typeof(AppearanceComponent))]
+[ComponentReference(typeof(AppearanceComponent)), Friend(typeof(AppearanceSystem))]
 public sealed class ClientAppearanceComponent : AppearanceComponent
 {
-    [ViewVariables]
-    private bool _appearanceDirty;
-
     [ViewVariables]
     [DataField("visuals")]
     internal List<AppearanceVisualizer> Visualizers = new();
-
-    protected override void MarkDirty()
-    {
-        if (_appearanceDirty)
-            return;
-
-        EntitySystem.Get<AppearanceSystem>().EnqueueUpdate(this);
-        _appearanceDirty = true;
-    }
-
-    protected override void Initialize()
-    {
-        base.Initialize();
-
-        foreach (var visual in Visualizers)
-        {
-            visual.InitializeEntity(Owner);
-        }
-
-        MarkDirty();
-    }
-
-    internal void UnmarkDirty()
-    {
-        _appearanceDirty = false;
-    }
 }

Robust.Client/GameObjects/Components/Eye/EyeComponent.cs

@@ -9,7 +9,7 @@ using Robust.Shared.ViewVariables;
 namespace Robust.Client.GameObjects
 {
     [ComponentReference(typeof(SharedEyeComponent))]
-    public class EyeComponent : SharedEyeComponent
+    public sealed class EyeComponent : SharedEyeComponent
     {
         [Dependency] private readonly IEyeManager _eyeManager = default!;
         [Dependency] private readonly IEntityManager _entityManager = default!;

Robust.Client/GameObjects/Components/Icon/IconComponent.cs

@@ -12,7 +12,7 @@ using Robust.Shared.Utility;
 namespace Robust.Client.GameObjects
 {
     [RegisterComponent]
-    public class IconComponent : Component, ISerializationHooks
+    public sealed class IconComponent : Component, ISerializationHooks
     {
         public IDirectionalTextureProvider? Icon { get; private set; }
 

Robust.Client/GameObjects/Components/Input/InputComponent.cs

@@ -8,7 +8,7 @@ namespace Robust.Client.GameObjects
     /// <summary>
     ///     Defines data fields used in the <see cref="InputSystem"/>.
     /// </summary>
-    public class InputComponent : Component
+    public sealed class InputComponent : Component
     {
         /// <summary>
         ///     The context that will be made active for a client that attaches to this entity.

Robust.Client/GameObjects/Components/Light/ClientOccluderComponent.cs

@@ -8,7 +8,7 @@ using Robust.Shared.ViewVariables;
 namespace Robust.Client.GameObjects
 {
     [ComponentReference(typeof(OccluderComponent))]
-    internal sealed class ClientOccluderComponent : OccluderComponent
+    public sealed class ClientOccluderComponent : OccluderComponent
     {
         [Dependency] private readonly IMapManager _mapManager = default!;
         [Dependency] private readonly IEntityManager _entityManager = default!;
@@ -40,13 +40,14 @@ namespace Robust.Client.GameObjects
 
         public void AnchorStateChanged()
         {
-            SendDirty();
+            var xform = _entityManager.GetComponent<TransformComponent>(Owner);
+            SendDirty(xform);
 
-            if(!_entityManager.GetComponent<TransformComponent>(Owner).Anchored)
+            if(!xform.Anchored)
                 return;
 
-            var grid = _mapManager.GetGrid(_entityManager.GetComponent<TransformComponent>(Owner).GridID);
-            _lastPosition = (_entityManager.GetComponent<TransformComponent>(Owner).GridID, grid.TileIndicesFor(_entityManager.GetComponent<TransformComponent>(Owner).Coordinates));
+            var grid = _mapManager.GetGrid(xform.GridID);
+            _lastPosition = (xform.GridID, grid.TileIndicesFor(xform.Coordinates));
         }
 
         protected override void Shutdown()
@@ -56,9 +57,10 @@ namespace Robust.Client.GameObjects
             SendDirty();
         }
 
-        private void SendDirty()
+        private void SendDirty(TransformComponent? xform = null)
         {
-            if (_entityManager.GetComponent<TransformComponent>(Owner).Anchored)
+            xform ??= _entityManager.GetComponent<TransformComponent>(Owner);
+            if (xform.Anchored)
             {
                 _entityManager.EventBus.RaiseEvent(EventSource.Local,
                     new OccluderDirtyEvent(Owner, _lastPosition));
@@ -69,13 +71,29 @@ namespace Robust.Client.GameObjects
         {
             Occluding = OccluderDir.None;
 
-            if (Deleted || !_entityManager.GetComponent<TransformComponent>(Owner).Anchored)
+            if (Deleted)
+                return;
+
+            // Content may want to override the default behavior for occlusion.
+            var xform = _entityManager.GetComponent<TransformComponent>(Owner);
+            var ev = new OccluderDirectionsEvent
             {
+                Component = xform,
+            };
+
+            _entityManager.EventBus.RaiseLocalEvent(Owner, ref ev);
+
+            if (ev.Handled)
+            {
+                Occluding = ev.Directions;
                 return;
             }
 
-            var grid = _mapManager.GetGrid(_entityManager.GetComponent<TransformComponent>(Owner).GridID);
-            var position = _entityManager.GetComponent<TransformComponent>(Owner).Coordinates;
+            if (!xform.Anchored)
+                return;
+
+            var grid = _mapManager.GetGrid(xform.GridID);
+            var position = xform.Coordinates;
             void CheckDir(Direction dir, OccluderDir oclDir)
             {
                 foreach (var neighbor in grid.GetInDir(position, dir))
@@ -88,7 +106,7 @@ namespace Robust.Client.GameObjects
                 }
             }
 
-            var angle = _entityManager.GetComponent<TransformComponent>(Owner).LocalRotation;
+            var angle = xform.LocalRotation;
             var dirRolling = angle.GetCardinalDir();
             // dirRolling starts at effective south
 
@@ -103,15 +121,28 @@ namespace Robust.Client.GameObjects
 
             CheckDir(dirRolling, OccluderDir.East);
         }
+    }
 
-        [Flags]
-        internal enum OccluderDir : byte
-        {
-            None = 0,
-            North = 1,
-            East = 1 << 1,
-            South = 1 << 2,
-            West = 1 << 3,
-        }
+    [Flags]
+    public enum OccluderDir : byte
+    {
+        None = 0,
+        North = 1,
+        East = 1 << 1,
+        South = 1 << 2,
+        West = 1 << 3,
+    }
+
+    /// <summary>
+    /// Raised by occluders when trying to get occlusion directions.
+    /// </summary>
+    [ByRefEvent]
+    public struct OccluderDirectionsEvent
+    {
+        public bool Handled = false;
+        public OccluderDir Directions = OccluderDir.None;
+        public TransformComponent Component = default!;
+
+        public OccluderDirectionsEvent() {}
     }
 }

Robust.Client/GameObjects/Components/Light/PointLightComponent.cs

@@ -11,7 +11,7 @@ namespace Robust.Client.GameObjects
 {
     [RegisterComponent]
     [ComponentReference(typeof(SharedPointLightComponent))]
-    public class PointLightComponent : SharedPointLightComponent, ISerializationHooks
+    public sealed class PointLightComponent : SharedPointLightComponent, ISerializationHooks
     {
         [Dependency] private readonly IEntityManager _entityManager = default!;
 
@@ -139,7 +139,7 @@ namespace Robust.Client.GameObjects
         internal RenderingTreeComponent? RenderTree { get; set; }
     }
 
-    public class PointLightRadiusChangedEvent : EntityEventArgs
+    public sealed class PointLightRadiusChangedEvent : EntityEventArgs
     {
         public PointLightComponent PointLightComponent { get; }
 

Robust.Client/GameObjects/Components/Renderable/ISpriteComponent.cs

@@ -119,7 +119,8 @@ namespace Robust.Client.GameObjects
         ///     This is useful to allow layer map configs to be defined in prototypes,
         ///     while still allowing code to create configs if they're absent.
         /// </remarks>
-        void LayerMapReserveBlank(object key);
+        /// <returns>Index of the new layer.</returns>
+        int LayerMapReserveBlank(object key);
 
         /// <summary>
         ///     Adds a layer without texture (thus falling back to the error texture).
@@ -145,8 +146,8 @@ namespace Robust.Client.GameObjects
         void RemoveLayer(int layer);
         void RemoveLayer(object layerKey);
 
-        void LayerSetShader(int layer, ShaderInstance shader);
-        void LayerSetShader(object layerKey, ShaderInstance shader);
+        void LayerSetShader(int layer, ShaderInstance shader, string? prototype = null);
+        void LayerSetShader(object layerKey, ShaderInstance shader, string? prototype = null);
         void LayerSetShader(int layer, string shaderName);
         void LayerSetShader(object layerKey, string shaderName);
 
@@ -217,8 +218,8 @@ namespace Robust.Client.GameObjects
         int GetLayerDirectionCount(ISpriteLayer layer);
 
         /// <summary>
-        ///     Calculate sprite bounding box in world-space coordinates.
+        ///     Calculate the rotated sprite bounding box in world-space coordinates.
         /// </summary>
-        Box2 CalculateBoundingBox(Vector2 worldPos);
+        Box2Rotated CalculateRotatedBoundingBox(Vector2 worldPosition, Angle worldRotation, IEye? eye = null);
     }
 }

Robust.Client/GameObjects/Components/Renderable/ISpriteLayer.cs

@@ -25,8 +25,6 @@ namespace Robust.Client.GameObjects
 
         RSI.State.Direction EffectiveDirection(Angle worldRotation);
 
-        Vector2 LocalToLayer(Vector2 localPos);
-
         /// <summary>
         ///     Layer size in pixels.
         ///     Don't account layer scale or sprite world transform.
@@ -37,6 +35,6 @@ namespace Robust.Client.GameObjects
         ///     Calculate layer bounding box in sprite local-space coordinates.
         /// </summary>
         /// <returns>Bounding box in sprite local-space coordinates.</returns>
-        Box2 CalculateBoundingBox();
+        Box2 CalculateBoundingBox(Angle worldAngle);
     }
 }

Robust.Client/GameObjects/Components/Renderable/SpriteBoundsOverlay.cs

@@ -57,7 +57,7 @@ namespace Robust.Client.GameObjects
         private bool _enabled;
     }
 
-    public class SpriteBoundsOverlay : Overlay
+    public sealed class SpriteBoundsOverlay : Overlay
     {
         public override OverlaySpace Space => OverlaySpace.WorldSpace;
 
@@ -84,10 +84,16 @@ namespace Robust.Client.GameObjects
 
                 foreach (var sprite in comp.SpriteTree.QueryAabb(localAABB))
                 {
-                    var worldPos = _entityManager.GetComponent<TransformComponent>(sprite.Owner).WorldPosition;
-                    var bounds = sprite.CalculateBoundingBox(worldPos);
+                    var (worldPos, worldRot) = _entityManager.GetComponent<TransformComponent>(sprite.Owner).GetWorldPositionRotation();
+                    var bounds = sprite.CalculateRotatedBoundingBox(worldPos, worldRot);
+
+                    // Get scaled down bounds used to indicate the "south" of a sprite.
+                    var localBound = bounds.Box;
+                    var smallLocal = localBound.Scale(0.2f).Translated(-new Vector2(0f, localBound.Extents.Y));
+                    var southIndicator = new Box2Rotated(smallLocal, bounds.Rotation, bounds.Origin);
+
                     handle.DrawRect(bounds, Color.Red.WithAlpha(0.2f));
-                    handle.DrawRect(bounds.Scale(0.2f).Translated(-new Vector2(0f, bounds.Extents.Y)), Color.Blue.WithAlpha(0.5f));
+                    handle.DrawRect(southIndicator, Color.Blue.WithAlpha(0.5f));
                 }
             }
         }

Robust.Client/GameObjects/Components/Renderable/SpriteComponent.cs

@@ -20,6 +20,7 @@ using Robust.Shared.Serialization.TypeSerializers.Implementations.Custom;
 using Robust.Shared.Utility;
 using Robust.Shared.ViewVariables;
 using DrawDepthTag = Robust.Shared.GameObjects.DrawDepth;
+using RSIDirection = Robust.Client.Graphics.RSI.State.Direction;
 
 namespace Robust.Client.GameObjects
 {
@@ -31,6 +32,8 @@ namespace Robust.Client.GameObjects
         [Dependency] private readonly IResourceCache resourceCache = default!;
         [Dependency] private readonly IPrototypeManager prototypes = default!;
         [Dependency] private readonly IEntityManager entities = default!;
+        [Dependency] private readonly IReflectionManager reflection = default!;
+        [Dependency] private readonly IEyeManager eyeManager = default!;
 
         [DataField("visible")]
         private bool _visible = true;
@@ -72,7 +75,11 @@ namespace Robust.Client.GameObjects
         public Vector2 Scale
         {
             get => scale;
-            set => scale = value;
+            set
+            {
+                scale = value;
+                UpdateLocalMatrix();
+            }
         }
 
         [DataField("rotation")]
@@ -83,7 +90,11 @@ namespace Robust.Client.GameObjects
         public Angle Rotation
         {
             get => rotation;
-            set => rotation = value;
+            set
+            {
+                rotation = value;
+                UpdateLocalMatrix();
+            }
         }
 
         [DataField("offset")]
@@ -97,12 +108,18 @@ namespace Robust.Client.GameObjects
         public Vector2 Offset
         {
             get => offset;
-            set => offset = value;
+            set
+            {
+                offset = value;
+                UpdateLocalMatrix();
+            }
         }
 
         [DataField("color")]
         private Color color = Color.White;
 
+        public Matrix3 LocalMatrix = Matrix3.Identity;
+
         [Animatable]
         [ViewVariables(VVAccess.ReadWrite)]
         public Color Color
@@ -134,113 +151,7 @@ namespace Robust.Client.GameObjects
                 Layers.Clear();
                 foreach (var layerDatum in value)
                 {
-                    var anyTextureAttempted = false;
-                    var layer = new Layer(this);
-                    if (!string.IsNullOrWhiteSpace(layerDatum.RsiPath))
-                    {
-                        var path = TextureRoot / layerDatum.RsiPath;
-
-                        if (IoCManager.Resolve<IResourceCache>().TryGetResource(path, out RSIResource? resource))
-                        {
-                            layer.RSI = resource.RSI;
-                        }
-                        else
-                        {
-                            Logger.ErrorS(LogCategory, "Unable to load layer RSI '{0}'.", path);
-                        }
-                    }
-
-                    if (!string.IsNullOrWhiteSpace(layerDatum.State))
-                    {
-                        anyTextureAttempted = true;
-                        var theRsi = layer.RSI ?? BaseRSI;
-                        if (theRsi == null)
-                        {
-                            Logger.ErrorS(LogCategory,
-                                "Layer has no RSI to load states from. Cannot use 'state' property. ({0})",
-                                layerDatum.State);
-                        }
-                        else
-                        {
-                            var stateid = new RSI.StateId(layerDatum.State);
-                            layer.State = stateid;
-                            if (theRsi.TryGetState(stateid, out var state))
-                            {
-                                // Always use south because this layer will be cached in the serializer.
-                                layer.AnimationTimeLeft = state.GetDelay(0);
-                            }
-                            else
-                            {
-                                Logger.ErrorS(LogCategory,
-                                    $"State '{stateid}' not found in RSI: '{theRsi.Path}'.",
-                                    stateid);
-                            }
-                        }
-                    }
-
-                    if (!string.IsNullOrWhiteSpace(layerDatum.TexturePath))
-                    {
-                        anyTextureAttempted = true;
-                        if (layer.State.IsValid)
-                        {
-                            Logger.ErrorS(LogCategory,
-                                "Cannot specify 'texture' on a layer if it has an RSI state specified."
-                            );
-                        }
-                        else
-                        {
-                            layer.Texture =
-                                IoCManager.Resolve<IResourceCache>().GetResource<TextureResource>(TextureRoot / layerDatum.TexturePath);
-                        }
-                    }
-
-                    if (!string.IsNullOrWhiteSpace(layerDatum.Shader))
-                    {
-                        if (IoCManager.Resolve<IPrototypeManager>().TryIndex<ShaderPrototype>(layerDatum.Shader, out var prototype))
-                        {
-                            layer.Shader = prototype.Instance();
-                        }
-                        else
-                        {
-                            Logger.ErrorS(LogCategory,
-                                "Shader prototype '{0}' does not exist.",
-                                layerDatum.Shader);
-                        }
-                    }
-
-                    layer.Color = layerDatum.Color;
-                    layer.Rotation = layerDatum.Rotation;
-                    layer._offset = layerDatum.Offset;
-                    // If neither state: nor texture: were provided we assume that they want a blank invisible layer.
-                    layer.Visible = anyTextureAttempted && layerDatum.Visible;
-                    layer.Scale = layerDatum.Scale;
-
-                    Layers.Add(layer);
-
-                    if (layerDatum.MapKeys != null)
-                    {
-                        var index = Layers.Count - 1;
-                        foreach (var keyString in layerDatum.MapKeys)
-                        {
-                            object key;
-                            if (IoCManager.Resolve<IReflectionManager>().TryParseEnumReference(keyString, out var @enum))
-                            {
-                                key = @enum;
-                            }
-                            else
-                            {
-                                key = keyString;
-                            }
-
-                            if (LayerMap.ContainsKey(key))
-                            {
-                                Logger.ErrorS(LogCategory, "Duplicate layer map key definition: {0}", key);
-                                continue;
-                            }
-
-                            LayerMap.Add(key, index);
-                        }
-                    }
+                    AddLayer(layerDatum);
                 }
 
                 _layerMapShared = true;
@@ -336,11 +247,13 @@ namespace Robust.Client.GameObjects
 
         void ISerializationHooks.AfterDeserialization()
         {
+            IoCManager.InjectDependencies(this);
+
             {
                 if (!string.IsNullOrWhiteSpace(rsi))
                 {
                     var rsiPath = TextureRoot / rsi;
-                    if(IoCManager.Resolve<IResourceCache>().TryGetResource(rsiPath, out RSIResource? resource))
+                    if(resourceCache.TryGetResource(rsiPath, out RSIResource? resource))
                     {
                         BaseRSI = resource.RSI;
                     }
@@ -373,6 +286,8 @@ namespace Robust.Client.GameObjects
                 LayerMap.Clear();
                 LayerDatums = layerDatums;
             }
+
+            UpdateLocalMatrix();
         }
 
         /// <summary>
@@ -390,6 +305,7 @@ namespace Robust.Client.GameObjects
             offset = other.offset;
             rotation = other.rotation;
             scale = other.scale;
+            UpdateLocalMatrix();
             drawDepth = other.drawDepth;
             _screenLock = other._screenLock;
             _overrideDirection = other._overrideDirection;
@@ -415,9 +331,14 @@ namespace Robust.Client.GameObjects
             RenderOrder = other.RenderOrder;
         }
 
+        internal void UpdateLocalMatrix()
+        {
+            LocalMatrix = Matrix3.CreateTransform(in offset, in rotation, in scale);
+        }
+
         public Matrix3 GetLocalMatrix()
         {
-            return Matrix3.CreateTransform(in offset, in rotation, in scale);
+            return LocalMatrix;
         }
 
         /// <inheritdoc />
@@ -462,14 +383,17 @@ namespace Robust.Client.GameObjects
             _layerMapShared = false;
         }
 
-        public void LayerMapReserveBlank(object key)
+        public int LayerMapReserveBlank(object key)
         {
-            if (LayerMapTryGet(key, out var _))
+            if (LayerMapTryGet(key, out var index))
             {
-                return;
+                return index;
             }
 
-            LayerMapSet(key, AddBlankLayer());
+            index = AddBlankLayer();
+            LayerMapSet(key, index);
+
+            return index;
         }
 
         public int AddBlankLayer(int? newIndex = null)
@@ -478,6 +402,19 @@ namespace Robust.Client.GameObjects
             return AddLayer(layer, newIndex);
         }
 
+        /// <summary>
+        ///     Add a new layer based on some <see cref="PrototypeLayerData"/>.
+        /// </summary>
+        public int AddLayer(PrototypeLayerData layerDatum, int? newIndex = null)
+        {
+            var layer = new Layer(this);
+
+            var index = AddLayer(layer, newIndex);
+
+            LayerSetData(index, layerDatum);
+            return index;
+        }
+
         public int AddLayer(string texturePath, int? newIndex = null)
         {
             return AddLayer(new ResourcePath(texturePath), newIndex);
@@ -653,7 +590,144 @@ namespace Robust.Client.GameObjects
             RemoveLayer(layer);
         }
 
-        public void LayerSetShader(int layer, ShaderInstance? shader)
+        /// <summary>
+        ///     Fills in a layer's values using some <see cref="PrototypeLayerData"/>.
+        /// </summary>
+        public void LayerSetData(int index, PrototypeLayerData layerDatum)
+        {
+            if (Layers.Count <= index)
+            {
+                Logger.ErrorS(LogCategory, "Layer with index '{0}' does not exist, cannot set layer data! Trace:\n{1}",
+                    index, Environment.StackTrace);
+                return;
+            }
+
+            var layer = Layers[index];
+
+            var anyTextureAttempted = false;
+
+            if (!string.IsNullOrWhiteSpace(layerDatum.RsiPath))
+            {
+                var path = TextureRoot / layerDatum.RsiPath;
+
+                if (resourceCache.TryGetResource(path, out RSIResource? resource))
+                {
+                    layer.RSI = resource.RSI;
+                }
+                else
+                {
+                    Logger.ErrorS(LogCategory, "Unable to load layer RSI '{0}'.", path);
+                }
+            }
+
+            if (!string.IsNullOrWhiteSpace(layerDatum.State))
+            {
+                anyTextureAttempted = true;
+                var theRsi = layer.RSI ?? BaseRSI;
+                if (theRsi == null)
+                {
+                    Logger.ErrorS(LogCategory,
+                        "Layer has no RSI to load states from. Cannot use 'state' property. ({0})",
+                        layerDatum.State);
+                }
+                else
+                {
+                    var stateid = new RSI.StateId(layerDatum.State);
+                    layer.State = stateid;
+                    if (theRsi.TryGetState(stateid, out var state))
+                    {
+                        // Always use south because this layer will be cached in the serializer.
+                        layer.AnimationTimeLeft = state.GetDelay(0);
+                    }
+                    else
+                    {
+                        Logger.ErrorS(LogCategory,
+                            $"State '{stateid}' not found in RSI: '{theRsi.Path}'.",
+                            stateid);
+                    }
+                }
+            }
+
+            if (!string.IsNullOrWhiteSpace(layerDatum.TexturePath))
+            {
+                anyTextureAttempted = true;
+                if (layer.State.IsValid)
+                {
+                    Logger.ErrorS(LogCategory,
+                        "Cannot specify 'texture' on a layer if it has an RSI state specified."
+                    );
+                }
+                else
+                {
+                    layer.Texture =
+                        resourceCache.GetResource<TextureResource>(TextureRoot / layerDatum.TexturePath);
+                }
+            }
+
+            if (!string.IsNullOrWhiteSpace(layerDatum.Shader))
+            {
+                if (prototypes.TryIndex<ShaderPrototype>(layerDatum.Shader, out var prototype))
+                {
+                    layer.ShaderPrototype = layerDatum.Shader;
+                    layer.Shader = prototype.Instance();
+                }
+                else
+                {
+                    Logger.ErrorS(LogCategory,
+                        "Shader prototype '{0}' does not exist.",
+                        layerDatum.Shader);
+                }
+            }
+
+            if (layerDatum.MapKeys != null)
+            {
+                foreach (var keyString in layerDatum.MapKeys)
+                {
+                    object key;
+                    if (reflection.TryParseEnumReference(keyString, out var @enum))
+                    {
+                        key = @enum;
+                    }
+                    else
+                    {
+                        key = keyString;
+                    }
+
+                    if (LayerMap.TryGetValue(key, out var mappedIndex))
+                    {
+                        if (mappedIndex != index)
+                            Logger.ErrorS(LogCategory, "Duplicate layer map key definition: {0}", key);
+                        continue;
+                    }
+
+                    _layerMapEnsurePrivate();
+                    LayerMap[key] = index;
+                }
+            }
+
+            layer.Color = layerDatum.Color;
+            layer._rotation = layerDatum.Rotation;
+            layer._offset = layerDatum.Offset;
+            layer._scale = layerDatum.Scale;
+            layer.UpdateLocalMatrix();
+
+            // If neither state: nor texture: were provided we assume that they want a blank invisible layer.
+            layer.Visible = anyTextureAttempted && layerDatum.Visible;
+        }
+
+        public void LayerSetData(object layerKey, PrototypeLayerData data)
+        {
+            if (!LayerMapTryGet(layerKey, out var layer))
+            {
+                Logger.ErrorS(LogCategory, "Layer with key '{0}' does not exist, cannot set shader! Trace:\n{1}",
+                    layerKey, Environment.StackTrace);
+                return;
+            }
+
+            LayerSetData(layer, data);
+        }
+
+        public void LayerSetShader(int layer, ShaderInstance? shader, string? prototype = null)
         {
             if (Layers.Count <= layer)
             {
@@ -664,9 +738,10 @@ namespace Robust.Client.GameObjects
 
             var theLayer = Layers[layer];
             theLayer.Shader = shader;
+            theLayer.ShaderPrototype = prototype;
         }
 
-        public void LayerSetShader(object layerKey, ShaderInstance shader)
+        public void LayerSetShader(object layerKey, ShaderInstance shader, string? prototype = null)
         {
             if (!LayerMapTryGet(layerKey, out var layer))
             {
@@ -675,7 +750,7 @@ namespace Robust.Client.GameObjects
                 return;
             }
 
-            LayerSetShader(layer, shader);
+            LayerSetShader(layer, shader, prototype);
         }
 
         public void LayerSetShader(int layer, string shaderName)
@@ -684,10 +759,12 @@ namespace Robust.Client.GameObjects
             {
                 Logger.ErrorS(LogCategory, "Shader prototype '{0}' does not exist. Trace:\n{1}", shaderName,
                     Environment.StackTrace);
+
+                LayerSetShader(layer, null, null);
+                return;
             }
 
-            // This will set the shader to null if it does not exist.
-            LayerSetShader(layer, prototype?.Instance());
+            LayerSetShader(layer, prototype.Instance(), shaderName);
         }
 
         public void LayerSetShader(object layerKey, string shaderName)
@@ -1148,7 +1225,7 @@ namespace Robust.Client.GameObjects
                 return;
             }
 
-            Layers[layer].SetOffset(layerOffset);
+            Layers[layer].Offset = layerOffset;
         }
 
         public void LayerSetOffset(object layerKey, Vector2 layerOffset)
@@ -1230,25 +1307,6 @@ namespace Robust.Client.GameObjects
             RenderInternal(drawingHandle, eyeRotation, worldRotation, worldPosition, overrideDir);
         }
 
-        private void CalcModelMatrix(int numDirs, Angle eyeRotation, Angle worldRotation, Vector2 worldPosition, out Matrix3 modelMatrix)
-        {
-            Angle angle;
-
-            if (_screenLock)
-            {
-                // Negate the eye rotation in the model matrix, so that later when the view matrix is applied the
-                // sprite will be locked upright to the screen
-                angle = new Angle(-eyeRotation.Theta);
-            }
-            else
-            {
-                angle = CalcRectWorldAngle(worldRotation + eyeRotation, numDirs) - eyeRotation;
-            }
-
-            var sWorldRotation = angle;
-            modelMatrix = Matrix3.CreateTransform(in worldPosition, in sWorldRotation);
-        }
-
         private void RenderInternal(DrawingHandleWorld drawingHandle, Angle eyeRotation, Angle worldRotation, Vector2 worldPosition, Direction? overrideDirection)
         {
             // Reduce the angles to fix math shenanigans
@@ -1257,56 +1315,16 @@ namespace Robust.Client.GameObjects
             if (worldRotation.Theta < 0)
                 worldRotation = new Angle(worldRotation.Theta + Math.Tau);
 
-            // sprite matrix, WITHOUT offset.
-            // offset is applied after sprite numDirs snapping/rotation correction
-            // --> apply at same time as layer offset
-            var spriteMatrix = Matrix3.CreateTransform(Vector2.Zero, rotation, scale);
+            // worldRotation + eyeRotation should be the angle of the entity on-screen. If no-rot is enabled this is just set to zero.
+            // However, at some point later the eye-matrix is applied separately, so we subtract -eye rotation for now:
+            var entityMatrix = Matrix3.CreateTransform(worldPosition, NoRotation ? -eyeRotation : worldRotation);
 
+            Matrix3.Multiply(ref LocalMatrix, ref entityMatrix, out var transform);
+
+            var angle = worldRotation + eyeRotation; // angle on-screen. Used to decide the direction of 4/8 directional RSIs
             foreach (var layer in Layers)
             {
-                if (!layer.Visible)
-                {
-                    continue;
-                }
-
-                var numDirs = GetLayerDirectionCount(layer);
-                var layerRotation = worldRotation + layer.Rotation;
-                var layerPosition = worldPosition + layerRotation.RotateVec(layer._offset + offset);
-
-                CalcModelMatrix(numDirs, eyeRotation, layerRotation, layerPosition, out var modelMatrix);
-                Matrix3.Multiply(ref spriteMatrix, ref modelMatrix, out var transformMatrix);
-                drawingHandle.SetTransform(in transformMatrix);
-
-                RenderLayer(drawingHandle, layer, eyeRotation, layerRotation, overrideDirection);
-            }
-        }
-
-        private void RenderLayer(DrawingHandleWorld drawingHandle, Layer layer, Angle eyeRotation, Angle worldRotation, Direction? overrideDirection)
-        {
-            var texture = GetRenderTexture(layer, worldRotation + eyeRotation, overrideDirection);
-
-            if (layer.Shader != null)
-            {
-                drawingHandle.UseShader(layer.Shader);
-            }
-
-            var layerColor = color * layer.Color;
-
-            var position = -(Vector2)texture.Size / (2f * EyeManager.PixelsPerMeter);
-            var textureSize = texture.Size / (float)EyeManager.PixelsPerMeter;
-            var quad = Box2.FromDimensions(position, textureSize);
-
-            // TODO: Implement layer-specific rotation and scale.
-            // Apply these directly to the box.
-            // Oh and when you do update Layer.LocalToLayer so content doesn't break.
-
-            // handle.Modulate changes the color
-            // drawingHandle.SetTransform() is set above, turning the quad into local space vertices
-            drawingHandle.DrawTextureRectRegion(texture, quad, layerColor);
-
-            if (layer.Shader != null)
-            {
-                drawingHandle.UseShader(null);
+                layer.Render(drawingHandle, ref transform, angle, overrideDirection);
             }
         }
 
@@ -1342,27 +1360,6 @@ namespace Robust.Client.GameObjects
             };
         }
 
-        private Texture GetRenderTexture(Layer layer, Angle worldRotation, Direction? overrideDirection)
-        {
-            var texture = layer.Texture;
-
-            if (layer.State.IsValid)
-            {
-                // Pull texture from RSI state instead.
-                var rsi = layer.RSI ?? BaseRSI;
-                if (rsi == null || !rsi.TryGetState(layer.State, out var state))
-                {
-                    state = GetFallbackState(resourceCache);
-                }
-
-                var layerSpecificDir = layer.EffectiveDirection(state, worldRotation, overrideDirection);
-                texture = state.GetFrame(layerSpecificDir, layer.AnimationFrame);
-            }
-
-            texture ??= resourceCache.GetFallback<TextureResource>().Texture;
-            return texture;
-        }
-
         public void FrameUpdate(float delta)
         {
             foreach (var t in Layers)
@@ -1417,12 +1414,14 @@ namespace Robust.Client.GameObjects
 
             Visible = thestate.Visible;
             DrawDepth = thestate.DrawDepth;
-            Scale = thestate.Scale;
-            Rotation = thestate.Rotation;
-            Offset = thestate.Offset;
+            scale = thestate.Scale;
+            rotation = thestate.Rotation;
+            offset = thestate.Offset;
+            UpdateLocalMatrix();
             Color = thestate.Color;
             RenderOrder = thestate.RenderOrder;
 
+
             if (thestate.BaseRsiPath != null && BaseRSI != null)
             {
                 if (resourceCache.TryGetResource<RSIResource>(TextureRoot / thestate.BaseRsiPath, out var res))
@@ -1438,43 +1437,8 @@ namespace Robust.Client.GameObjects
                 }
             }
 
-            // Maybe optimize this to NOT full clear.
-            Layers.Clear();
-            for (var i = 0; i < thestate.Layers.Count; i++)
-            {
-                var netlayer = thestate.Layers[i];
-                var layer = new Layer(this)
-                {
-                    // These are easy so do them here.
-                    Scale = netlayer.Scale,
-                    Rotation = netlayer.Rotation,
-                    Visible = netlayer.Visible,
-                    Color = netlayer.Color
-                };
-                Layers.Add(layer);
-
-                // Using the public API to handle errors.
-                // Probably slow as crap.
-                // Who am I kidding, DEFINITELY.
-                if (netlayer.Shader != null)
-                {
-                    LayerSetShader(i, netlayer.Shader);
-                }
-
-                if (netlayer.RsiPath != null)
-                {
-                    LayerSetRSI(i, netlayer.RsiPath);
-                }
-
-                if (netlayer.TexturePath != null)
-                {
-                    LayerSetTexture(i, netlayer.TexturePath);
-                }
-                else if (netlayer.State != null)
-                {
-                    LayerSetState(i, netlayer.State);
-                }
-            }
+            // Maybe optimize this to NOT fully clear the layers. (see LayerDatums setter function)
+            LayerDatums = thestate.Layers;
         }
 
         private void QueueUpdateIsInert()
@@ -1553,35 +1517,61 @@ namespace Robust.Client.GameObjects
         }
 
         /// <inheritdoc/>
-        public Box2 CalculateBoundingBox(Vector2 worldPos)
+        public Box2Rotated CalculateRotatedBoundingBox(Vector2 worldPosition, Angle worldRotation, IEye? eye = null)
         {
             // fast check for empty sprites
-            if (Layers.Count == 0)
-                return new Box2(worldPos, worldPos);
+            if (!Visible || Layers.Count == 0)
+            {
+                return new Box2Rotated(new Box2(worldPosition, worldPosition), Angle.Zero, worldPosition);
+            }
+
+            // We need to modify world rotation so that it lies between 0 and 2pi.
+            // This matters for 4 or 8 directional sprites deciding which quadrant (octant?) they lie in.
+            // the 0->2pi convention is set by the sprite-rendering code that selects the layers.
+            // See RenderInternal().
+
+            worldRotation = worldRotation.Reduced();
+            if (worldRotation.Theta < 0)
+                worldRotation = new Angle(worldRotation.Theta + Math.Tau);
+
+            eye ??= eyeManager.CurrentEye;
+
+            // Need relative angle on screen for determining the sprite rsi direction.
+            Angle relativeRotation = NoRotation
+                ? Angle.Zero
+                : worldRotation + eye.Rotation;
 
             // we need to calculate bounding box taking into account all nested layers
-            // because layers can have offsets, scale or rotation we need to calculate a new BB
-            // based on lowest bottomLeft and hightest topRight points from all layers
-            var box = Layers[0].CalculateBoundingBox();
+            // because layers can have offsets, scale or rotation, we need to calculate a new BB
+            // based on lowest bottomLeft and highest topRight points from all layers
+            var box = Layers[0].CalculateBoundingBox(relativeRotation);
 
             for (int i = 1; i < Layers.Count; i++)
             {
                 var layer = Layers[i];
-                var layerBB = layer.CalculateBoundingBox();
+                if (!layer.Visible) continue;
+                var layerBB = layer.CalculateBoundingBox(relativeRotation);
 
                 box = box.Union(layerBB);
             }
 
-            // apply sprite transformations and calculate sprite bounding box
-            // we can optimize it a bit, if sprite doesn't have rotation
-            var spriteBox = box.Scale(Scale);
-            var spriteHasRotation = !Rotation.EqualsApprox(Angle.Zero);
-            var spriteBB = spriteHasRotation ?
-                new Box2Rotated(spriteBox, Rotation).CalcBoundingBox() : spriteBox;
+            // Next, what we do is take the box2 and apply the sprite's transform, and then the entity's transform. We
+            // could do this via Matrix3.TransformBox, but that only yields bounding boxes. So instead we manually
+            // transform our box by the combination of these matrices:
 
-            // move it all to world transform system (with sprite offset)
-            var worldBB = spriteBB.Translated(Offset + worldPos);
-            return worldBB;
+            if (Scale != Vector2.One)
+                box = box.Scale(Scale);
+
+            var adjustedOffset = NoRotation
+                ? (-eye.Rotation).RotateVec(Offset)
+                : worldRotation.RotateVec(Offset);
+
+            Vector2 position = adjustedOffset + worldPosition;
+            Angle finalRotation = NoRotation
+                ? Rotation - eye.Rotation
+                : Rotation + worldRotation;
+
+            return new Box2Rotated(box.Translated(position), finalRotation, position);
         }
 
         internal void UpdateBounds()
@@ -1615,10 +1605,11 @@ namespace Robust.Client.GameObjects
             Flip = 3,
         }
 
-        public class Layer : ISpriteLayer
+        public sealed class Layer : ISpriteLayer, ISerializationHooks
         {
             [ViewVariables] private readonly SpriteComponent _parent;
 
+            [ViewVariables] public string? ShaderPrototype;
             [ViewVariables] public ShaderInstance? Shader;
             [ViewVariables] public Texture? Texture;
 
@@ -1628,11 +1619,37 @@ namespace Robust.Client.GameObjects
             [ViewVariables] public float AnimationTime;
             [ViewVariables] public int AnimationFrame;
 
-            [ViewVariables(VVAccess.ReadWrite)]
-            public Vector2 Scale { get; set; } = Vector2.One;
+            public Matrix3 LocalMatrix = Matrix3.Identity;
 
             [ViewVariables(VVAccess.ReadWrite)]
-            public Angle Rotation { get; set; }
+            public Vector2 Scale
+            {
+                get => _scale;
+                set
+                {
+                    if (_scale.EqualsApprox(value)) return;
+
+                    _scale = value;
+                    UpdateLocalMatrix();
+                    _parent.UpdateBounds();
+                }
+            }
+            internal Vector2 _scale = Vector2.One;
+
+            [ViewVariables(VVAccess.ReadWrite)]
+            public Angle Rotation
+            {
+                get => _rotation;
+                set
+                {
+                    if (_rotation.EqualsApprox(value)) return;
+
+                    _rotation = value;
+                    UpdateLocalMatrix();
+                    _parent.UpdateBounds();
+                }
+            }
+            internal Angle _rotation = Angle.Zero;
 
             [ViewVariables(VVAccess.ReadWrite)]
             public bool Visible = true;
@@ -1652,6 +1669,7 @@ namespace Robust.Client.GameObjects
                     if (_offset.EqualsApprox(value)) return;
 
                     _offset = value;
+                    UpdateLocalMatrix();
                     _parent.UpdateBounds();
                 }
             }
@@ -1675,6 +1693,7 @@ namespace Robust.Client.GameObjects
                 if (toClone.Shader != null)
                 {
                     Shader = toClone.Shader.Mutable ? toClone.Shader.Duplicate() : toClone.Shader;
+                    ShaderPrototype = toClone.ShaderPrototype;
                 }
                 Texture = toClone.Texture;
                 RSI = toClone.RSI;
@@ -1682,14 +1701,26 @@ namespace Robust.Client.GameObjects
                 AnimationTimeLeft = toClone.AnimationTimeLeft;
                 AnimationTime = toClone.AnimationTime;
                 AnimationFrame = toClone.AnimationFrame;
-                Scale = toClone.Scale;
-                Rotation = toClone.Rotation;
+                _scale = toClone.Scale;
+                _rotation = toClone.Rotation;
+                _offset = toClone.Offset;
+                UpdateLocalMatrix();
                 Visible = toClone.Visible;
                 Color = toClone.Color;
                 DirOffset = toClone.DirOffset;
                 AutoAnimated = toClone.AutoAnimated;
             }
 
+            void ISerializationHooks.AfterDeserialization()
+            {
+                UpdateLocalMatrix();
+            }
+
+            internal void UpdateLocalMatrix()
+            {
+                LocalMatrix = Matrix3.CreateTransform(in _offset, in _rotation, in _scale);
+            }
+
             RSI? ISpriteLayer.Rsi { get => RSI; set => SetRsi(value); }
             RSI.StateId ISpriteLayer.RsiState { get => State; set => SetState(value); }
             Texture? ISpriteLayer.Texture { get => Texture; set => SetTexture(value); }
@@ -1701,7 +1732,7 @@ namespace Robust.Client.GameObjects
                     Color = Color,
                     Rotation = Rotation,
                     Scale = Scale,
-                    //todo Shader = Shader,
+                    Shader = ShaderPrototype,
                     State = State.Name,
                     Visible = Visible,
                     RsiPath = RSI?.Path?.ToString(),
@@ -1730,7 +1761,7 @@ namespace Robust.Client.GameObjects
                 set => SetAutoAnimated(value);
             }
 
-            public RSI.State.Direction EffectiveDirection(Angle worldRotation)
+            public RSIDirection EffectiveDirection(Angle worldRotation)
             {
                 if (State == default)
                 {
@@ -1751,22 +1782,16 @@ namespace Robust.Client.GameObjects
                 return default;
             }
 
-            public Vector2 LocalToLayer(Vector2 localPos)
-            {
-                // TODO: scale & rotation for layers is currently unimplemented.
-                return localPos;
-            }
-
-            public RSI.State.Direction EffectiveDirection(RSI.State state, Angle worldRotation,
+            public RSIDirection EffectiveDirection(RSI.State state, Angle worldRotation,
                 Direction? overrideDirection)
             {
                 if (state.Directions == RSI.State.DirectionType.Dir1)
                 {
-                    return RSI.State.Direction.South;
+                    return RSIDirection.South;
                 }
                 else
                 {
-                    RSI.State.Direction dir;
+                    RSIDirection dir;
                     if (overrideDirection != null)
                     {
                         dir = overrideDirection.Value.Convert(state.Directions);
@@ -1898,11 +1923,6 @@ namespace Robust.Client.GameObjects
                 _parent.QueueUpdateIsInert();
             }
 
-            public void SetOffset(Vector2 offset)
-            {
-                Offset = offset;
-            }
-
             /// <inheritdoc/>
             public Vector2i PixelSize
             {
@@ -1923,10 +1943,121 @@ namespace Robust.Client.GameObjects
             }
 
             /// <inheritdoc/>
-            public Box2 CalculateBoundingBox()
+            public Box2 CalculateBoundingBox(Angle angle)
             {
-                // TODO: scale & rotation for layers is currently unimplemented.
-                return Box2.CenteredAround(Offset, PixelSize / EyeManager.PixelsPerMeter);
+                // Other than some special cases for simple layers, this will basically just apply the matrix obtained
+                // via GetLayerDrawMatrix() to this layer's bounding box.
+
+                var rsiState = GetActualState();
+
+                var dir = (rsiState == null || rsiState.Directions == RSI.State.DirectionType.Dir1)
+                    ? RSIDirection.South
+                    : angle.ToRsiDirection(rsiState.Directions);
+
+                // special case for simple layers. The vast majority of layers are like this.
+                if (_rotation == Angle.Zero)
+                {
+                    var textureSize = PixelSize / EyeManager.PixelsPerMeter;
+
+                    // this switch block is basically an explicit version of the `rsiDirectionMatrix` in `GetLayerDrawMatrix()`.
+                    var box = dir switch
+                    {
+                        // No rotation:
+                        RSIDirection.South or RSIDirection.North => Box2.CenteredAround(Offset, textureSize),
+                        // rotate 90 degrees:
+                        RSIDirection.East or RSIDirection.West => Box2.CenteredAround(Offset, (textureSize.Y, textureSize.X)),
+                        // rotated 45 degrees (any 45 degree rotated rectangle has a square bounding box with sides of length (x+y)/sqrt(2) )
+                        _ => Box2.CenteredAround(Offset, Vector2.One * (textureSize.X + textureSize.Y) / MathF.Sqrt(2))
+                    };
+
+                    return _scale == Vector2.One ? box : box.Scale(_scale);
+                }
+
+                // Welp we have some non-zero _rotation, so lets just apply the generalized layer transform and get the bounding box from where;
+                GetLayerDrawMatrix(dir, out var layerDrawMatrix);
+                return layerDrawMatrix.TransformBox(Box2.CentredAroundZero(PixelSize / EyeManager.PixelsPerMeter));
+            }
+
+            internal RSI.State? GetActualState()
+            {
+                if (!State.IsValid)
+                    return null;
+
+                // Pull texture from RSI state
+                var rsi = RSI ?? _parent.BaseRSI;
+                if (rsi == null || !rsi.TryGetState(State, out var rsiState))
+                {
+                    rsiState = GetFallbackState(_parent.resourceCache);
+                }
+
+                return rsiState;
+            }
+
+            /// <summary>
+            ///     Given the apparent rotation of an entity on screen (world + eye rotation), get layer's matrix for drawing &
+            ///     relevant RSI direction.
+            /// </summary>
+            public void GetLayerDrawMatrix(RSIDirection dir, out Matrix3 layerDrawMatrix)
+            {
+                if (_parent.NoRotation)
+                    layerDrawMatrix = LocalMatrix;
+                else
+                {
+                    var rsiDirectionMatrix = Matrix3.CreateTransform(Vector2.Zero, -dir.Convert().ToAngle());
+                    Matrix3.Multiply(ref rsiDirectionMatrix, ref LocalMatrix, out layerDrawMatrix);
+                }
+            }
+
+            internal void Render(DrawingHandleWorld drawingHandle, ref Matrix3 spriteMatrix, Angle angle, Direction? overrideDirection)
+            {
+                if (!Visible)
+                    return;
+
+                var rsiState = GetActualState();
+
+                var dir = (rsiState == null || rsiState.Directions == RSI.State.DirectionType.Dir1)
+                    ? RSIDirection.South
+                    : angle.ToRsiDirection(rsiState.Directions);
+
+                // Set the drawing transform for this  layer
+                GetLayerDrawMatrix(dir, out var layerMatrix);
+                Matrix3.Multiply(ref layerMatrix, ref spriteMatrix, out var transformMatrix);
+                drawingHandle.SetTransform(in transformMatrix);
+
+                // The direction used to draw the sprite can differ from the one that the angle would naively suggest,
+                // due to direction overrides or offsets.
+                if (overrideDirection != null && rsiState != null)
+                    dir = overrideDirection.Value.Convert(rsiState.Directions);
+                dir = dir.OffsetRsiDir(DirOffset);
+
+                // Get the correct directional texture from the state, and draw it!
+                var texture = GetRenderTexture(rsiState, dir);
+                RenderTexture(drawingHandle, texture);
+            }
+
+            private void RenderTexture(DrawingHandleWorld drawingHandle, Texture texture)
+            {
+                if (Shader != null)
+                    drawingHandle.UseShader(Shader);
+
+                var layerColor = _parent.color * Color;
+
+                var position = -(Vector2)texture.Size / (2f * EyeManager.PixelsPerMeter);
+                var textureSize = texture.Size / (float)EyeManager.PixelsPerMeter;
+                var quad = Box2.FromDimensions(position, textureSize);
+
+                drawingHandle.DrawTextureRectRegion(texture, quad, layerColor);
+
+                if (Shader != null)
+                    drawingHandle.UseShader(null);
+            }
+
+            private Texture GetRenderTexture(RSI.State? state, RSIDirection dir)
+            {
+                if (state == null)
+                    return Texture ?? _parent.resourceCache.GetFallback<TextureResource>().Texture;
+
+                return state.GetFrame(dir, AnimationFrame);
             }
         }
 
@@ -2034,6 +2165,7 @@ namespace Robust.Client.GameObjects
             return results;
         }
 
+        [Obsolete("Use SpriteSystem")]
         public static IRsiStateLike GetPrototypeIcon(EntityPrototype prototype, IResourceCache resourceCache)
         {
             var icon = IconComponent.GetPrototypeIcon(prototype, resourceCache);

Robust.Client/GameObjects/Components/UserInterface/ClientUserInterfaceComponent.cs

@@ -11,7 +11,7 @@ using Robust.Shared.ViewVariables;
 namespace Robust.Client.GameObjects
 {
     [ComponentReference(typeof(SharedUserInterfaceComponent))]
-    public class ClientUserInterfaceComponent : SharedUserInterfaceComponent, ISerializationHooks
+    public sealed class ClientUserInterfaceComponent : SharedUserInterfaceComponent, ISerializationHooks
     {
         [Dependency] private readonly IReflectionManager _reflectionManager = default!;
         [Dependency] private readonly IDynamicTypeFactory _dynamicTypeFactory = default!;

Robust.Client/GameObjects/EntitySystems/AnimationPlayerSystem.cs

@@ -62,6 +62,12 @@ namespace Robust.Client.GameObjects
             Play(component, animation, key);
         }
 
+        public void Play(EntityUid uid, AnimationPlayerComponent? component, Animation animation, string key)
+        {
+            component ??= EntityManager.EnsureComponent<AnimationPlayerComponent>(uid);
+            Play(component, animation, key);
+        }
+
         /// <summary>
         ///     Start playing an animation.
         /// </summary>
@@ -79,6 +85,14 @@ namespace Robust.Client.GameObjects
                    component.PlayingAnimations.ContainsKey(key);
         }
 
+        public bool HasRunningAnimation(EntityUid uid, AnimationPlayerComponent? component, string key)
+        {
+            if (component == null)
+                TryComp(uid, out component);
+
+            return component != null && component.PlayingAnimations.ContainsKey(key);
+        }
+
         public bool HasRunningAnimation(AnimationPlayerComponent component, string key)
         {
             return component.PlayingAnimations.ContainsKey(key);
@@ -88,6 +102,18 @@ namespace Robust.Client.GameObjects
         {
             component.PlayingAnimations.Remove(key);
         }
+
+        public void Stop(EntityUid uid, string key)
+        {
+            if (!TryComp<AnimationPlayerComponent>(uid, out var player)) return;
+            player.PlayingAnimations.Remove(key);
+        }
+
+        public void Stop(EntityUid uid, AnimationPlayerComponent? component, string key)
+        {
+            if (!Resolve(uid, ref component, false)) return;
+            component.PlayingAnimations.Remove(key);
+        }
     }
 
     public sealed class AnimationCompletedEvent : EntityEventArgs

Robust.Client/GameObjects/EntitySystems/AppearanceSystem.cs

@@ -1,17 +1,95 @@
+using System;
 using System.Collections.Generic;
 using JetBrains.Annotations;
 using Robust.Shared.GameObjects;
+using Robust.Shared.GameStates;
 
 namespace Robust.Client.GameObjects
 {
     [UsedImplicitly]
-    internal sealed class AppearanceSystem : EntitySystem
+    public sealed class AppearanceSystem : SharedAppearanceSystem
     {
         private readonly Queue<ClientAppearanceComponent> _queuedUpdates = new();
 
-        public void EnqueueUpdate(ClientAppearanceComponent component)
+        public override void Initialize()
         {
-            _queuedUpdates.Enqueue(component);
+            base.Initialize();
+
+            SubscribeLocalEvent<ClientAppearanceComponent, ComponentInit>(OnAppearanceInit);
+            SubscribeLocalEvent<ClientAppearanceComponent, ComponentHandleState>(OnAppearanceHandleState);
+        }
+
+        private void OnAppearanceInit(EntityUid uid, ClientAppearanceComponent component, ComponentInit args)
+        {
+            foreach (var visual in component.Visualizers)
+            {
+                visual.InitializeEntity(uid);
+            }
+
+            MarkDirty(component);
+        }
+
+        private void OnAppearanceHandleState(EntityUid uid, ClientAppearanceComponent component, ref ComponentHandleState args)
+        {
+            if (args.Current is not AppearanceComponentState actualState)
+                return;
+
+            var stateDiff = component.AppearanceData.Count != actualState.Data.Count;
+
+            if (!stateDiff)
+            {
+                foreach (var (key, value) in component.AppearanceData)
+                {
+                    if (!actualState.Data.TryGetValue(key, out var stateValue) ||
+                        !value.Equals(stateValue))
+                    {
+                        stateDiff = true;
+                        break;
+                    }
+                }
+            }
+
+            if (!stateDiff) return;
+
+            component.AppearanceData = CloneAppearanceData(actualState.Data);
+            MarkDirty(component);
+        }
+
+        /// <summary>
+        ///     Take in an appearance data dictionary and attempt to clone it.
+        /// </summary>
+        /// <remarks>
+        ///     As some appearance data values are not simple value-type objects, this is not just a shallow clone.
+        /// </remarks>
+        private Dictionary<object, object> CloneAppearanceData(Dictionary<object, object> data)
+        {
+            Dictionary<object, object> newDict = new(data.Count);
+
+            foreach (var (key, value) in data)
+            {
+                if (value.GetType().IsValueType)
+                    newDict[key] = value;
+                else if (value is ICloneable cloneable)
+                    newDict[key] = cloneable.Clone();
+                else
+                    throw new NotSupportedException("Invalid object in appearance data dictionary. Appearance data must be cloneable");
+            }
+
+            return newDict;
+        }
+
+        public override void MarkDirty(AppearanceComponent component)
+        {
+            if (component.AppearanceDirty)
+                return;
+
+            _queuedUpdates.Enqueue((ClientAppearanceComponent) component);
+            component.AppearanceDirty = true;
+        }
+
+        internal void UnmarkDirty(ClientAppearanceComponent component)
+        {
+            component.AppearanceDirty = false;
         }
 
         public override void FrameUpdate(float frameTime)
@@ -22,7 +100,7 @@ namespace Robust.Client.GameObjects
                     continue;
 
                 OnChangeData(appearance.Owner, appearance);
-                appearance.UnmarkDirty();
+                UnmarkDirty(appearance);
             }
         }
 
@@ -30,10 +108,30 @@ namespace Robust.Client.GameObjects
         {
             if (!Resolve(uid, ref appearanceComponent, false)) return;
 
+            var ev = new AppearanceChangeEvent
+            {
+                Component = appearanceComponent,
+                AppearanceData = appearanceComponent.AppearanceData,
+            };
+
+            // Give it AppearanceData so we can still keep the friend attribute on the component.
+            EntityManager.EventBus.RaiseLocalEvent(uid, ref ev);
+
+            // Eventually visualizers would be nuked and we'd just make them components instead.
             foreach (var visualizer in appearanceComponent.Visualizers)
             {
                 visualizer.OnChangeData(appearanceComponent);
             }
         }
     }
+
+    /// <summary>
+    ///     Raised whenever the appearance data for an entity changes.
+    /// </summary>
+    [ByRefEvent]
+    public struct AppearanceChangeEvent
+    {
+        public AppearanceComponent Component;
+        public IReadOnlyDictionary<object, object> AppearanceData;
+    }
 }

Robust.Client/GameObjects/EntitySystems/AudioSystem.cs

@@ -17,7 +17,7 @@ using Robust.Shared.Utility;
 namespace Robust.Client.GameObjects
 {
     [UsedImplicitly]
-    public class AudioSystem : SharedAudioSystem, IAudioSystem
+    public sealed class AudioSystem : SharedAudioSystem, IAudioSystem
     {
         [Dependency] private readonly IResourceCache _resourceCache = default!;
         [Dependency] private readonly IMapManager _mapManager = default!;
@@ -420,7 +420,7 @@ namespace Robust.Client.GameObjects
             source.IsLooping = audioParams.Value.Loop;
         }
 
-        private class PlayingStream : IPlayingAudioStream
+        private sealed class PlayingStream : IPlayingAudioStream
         {
             public uint? NetIdentifier;
             public IClydeAudioSource Source = default!;

Robust.Client/GameObjects/EntitySystems/ClientOccluderSystem.cs

@@ -72,10 +72,13 @@ namespace Robust.Client.GameObjects
             var sender = ev.Sender;
             if (EntityManager.EntityExists(sender) &&
                 EntityManager.TryGetComponent(sender, out ClientOccluderComponent? iconSmooth)
-                && iconSmooth.Running)
+                && iconSmooth.Initialized)
             {
-                var grid1 = _mapManager.GetGrid(EntityManager.GetComponent<TransformComponent>(sender).GridID);
-                var coords = EntityManager.GetComponent<TransformComponent>(sender).Coordinates;
+                var xform = EntityManager.GetComponent<TransformComponent>(sender);
+                if (!_mapManager.TryGetGrid(xform.GridID, out var grid1))
+                    return;
+
+                var coords = xform.Coordinates;
 
                 _dirtyEntities.Enqueue(sender);
                 AddValidEntities(grid1.GetInDir(coords, Direction.North));
@@ -85,7 +88,7 @@ namespace Robust.Client.GameObjects
             }
 
             // Entity is no longer valid, update around the last position it was at.
-            if (ev.LastPosition.HasValue && _mapManager.TryGetGrid(ev.LastPosition.Value.grid, out var grid))
+            else if (ev.LastPosition.HasValue && _mapManager.TryGetGrid(ev.LastPosition.Value.grid, out var grid))
             {
                 var pos = ev.LastPosition.Value.pos;
 

Robust.Client/GameObjects/EntitySystems/ContainerSystem.cs

@@ -5,12 +5,14 @@ using Robust.Shared.Containers;
 using Robust.Shared.GameObjects;
 using Robust.Shared.GameStates;
 using Robust.Shared.IoC;
+using Robust.Shared.Log;
+using Robust.Shared.Map;
 using Robust.Shared.Serialization;
 using static Robust.Shared.Containers.ContainerManagerComponent;
 
 namespace Robust.Client.GameObjects
 {
-    public class ContainerSystem : SharedContainerSystem
+    public sealed class ContainerSystem : SharedContainerSystem
     {
         [Dependency] private readonly IRobustSerializer _serializer = default!;
         [Dependency] private readonly IDynamicTypeFactoryInternal _dynFactory = default!;
@@ -59,7 +61,7 @@ namespace Robust.Client.GameObjects
             {
                 if (!cast.ContainerSet.Any(data => data.Id == id))
                 {
-                    container.EmptyContainer(true);
+                    container.EmptyContainer(true, entMan: EntityManager);
                     container.Shutdown();
                     toDelete ??= new List<string>();
                     toDelete.Add(id);
@@ -131,12 +133,51 @@ namespace Robust.Client.GameObjects
                         continue;
                     }
 
+                    // If an entity is currently in the shadow realm, it means we probably left PVS and are now getting
+                    // back into range. We do not want to directly insert this entity, as IF the container and entity
+                    // transform states did not get sent simultaneously, the entity's transform will be modified by the
+                    // insert operation. This means it will then be reset to the shadow realm, causing it to be ejected
+                    // from the container. It would then subsequently be parented to the container without ever being
+                    // re-inserted, leading to the client seeing what should be hidden entities attached to
+                    // containers/players.
+                    if (Transform(entity).MapID == MapId.Nullspace)
+                    {
+                        AddExpectedEntity(entity, container);
+                        continue;
+                    }
+
                     if (!container.ContainedEntities.Contains(entity))
                         container.Insert(entity);
                 }
             }
         }
 
+        protected override void HandleParentChanged(ref EntParentChangedMessage message)
+        {
+            base.HandleParentChanged(ref message);
+
+            // If an entity warped in from null-space (i.e., re-entered PVS) and got attached to a container, do the same checks as for newly initialized entities.
+            if (message.OldParent != null && message.OldParent.Value.IsValid())
+                return;
+
+            if (!ExpectedEntities.TryGetValue(message.Entity, out var container))
+                return;
+
+            if (Transform(message.Entity).ParentUid != container.Owner)
+            {
+                // This container is expecting an entity... but it got parented to some other entity???
+                // Ah well, the sever should send a new container state that updates expected entities so just ignore it for now.
+                return;
+            }
+
+            RemoveExpectedEntity(message.Entity);
+
+            if (container.Deleted)
+                return;
+
+            container.Insert(message.Entity);
+        }
+
         private IContainer ContainerFactory(ContainerManagerComponent component, string containerType, string id)
         {
             var type = _serializer.FindSerializedType(typeof(IContainer), containerType);
@@ -169,68 +210,101 @@ namespace Robust.Client.GameObjects
         public override void FrameUpdate(float frameTime)
         {
             base.FrameUpdate(frameTime);
+            var pointQuery = EntityManager.GetEntityQuery<PointLightComponent>();
+            var spriteQuery = EntityManager.GetEntityQuery<SpriteComponent>();
+            var xformQuery = EntityManager.GetEntityQuery<TransformComponent>();
 
             foreach (var toUpdate in _updateQueue)
             {
-                if (EntityManager.Deleted(toUpdate))
-                {
+                if (Deleted(toUpdate))
                     continue;
-                }
 
-                UpdateEntityRecursively(toUpdate);
+                UpdateEntityRecursively(toUpdate, xformQuery, pointQuery, spriteQuery);
             }
 
             _updateQueue.Clear();
         }
 
-        private void UpdateEntityRecursively(EntityUid entity)
+        private void UpdateEntityRecursively(
+            EntityUid entity,
+            EntityQuery<TransformComponent> xformQuery,
+            EntityQuery<PointLightComponent> pointQuery,
+            EntityQuery<SpriteComponent> spriteQuery)
         {
-            // TODO: Since we are recursing down,
-            // we could cache ShowContents data here to speed it up for children.
-            // Am lazy though.
-            UpdateEntity(entity);
+            // Recursively go up parents and containers to see whether both sprites and lights need to be occluded
+            // Could maybe optimise this more by checking nearest parent that has sprite / light and whether it's container
+            // occluded but this probably isn't a big perf issue.
+            var xform = xformQuery.GetComponent(entity);
+            var parent = xform.ParentUid;
+            var child = entity;
+            var spriteOccluded = false;
+            var lightOccluded = false;
 
-            foreach (var child in EntityManager.GetComponent<TransformComponent>(entity).Children)
+            while (parent.IsValid() && !spriteOccluded && !lightOccluded)
             {
-                UpdateEntityRecursively(child.Owner);
+                var parentXform = xformQuery.GetComponent(parent);
+                if (TryComp<ContainerManagerComponent>(parent, out var manager) && manager.TryGetContainer(child, out var container))
+                {
+                    spriteOccluded = spriteOccluded || !container.ShowContents;
+                    lightOccluded = lightOccluded || container.OccludesLight;
+                }
+
+                child = parent;
+                parent = parentXform.ParentUid;
             }
+
+            // Alright so
+            // This is the CBT bit.
+            // The issue is we need to go through the children and re-check whether they are or are not contained.
+            // if they are contained then the occlusion values may need updating for all those children
+            UpdateEntity(entity, xform, xformQuery, pointQuery, spriteQuery, spriteOccluded, lightOccluded);
         }
 
-        private void UpdateEntity(EntityUid entity)
+        private void UpdateEntity(
+            EntityUid entity,
+            TransformComponent xform,
+            EntityQuery<TransformComponent> xformQuery,
+            EntityQuery<PointLightComponent> pointQuery,
+            EntityQuery<SpriteComponent> spriteQuery,
+            bool spriteOccluded,
+            bool lightOccluded)
         {
-            if (EntityManager.TryGetComponent(entity, out SpriteComponent? sprite))
+            if (spriteQuery.TryGetComponent(entity, out var sprite))
             {
-                sprite.ContainerOccluded = false;
-
-                // We have to recursively scan for containers upwards in case of nested containers.
-                var tempParent = entity;
-                while (tempParent.TryGetContainer(out var container))
-                {
-                    if (!container.ShowContents)
-                    {
-                        sprite.ContainerOccluded = true;
-                        break;
-                    }
-
-                    tempParent = container.Owner;
-                }
+                sprite.ContainerOccluded = spriteOccluded;
             }
 
-            if (EntityManager.TryGetComponent(entity, out PointLightComponent? light))
+            if (pointQuery.TryGetComponent(entity, out var light))
             {
-                light.ContainerOccluded = false;
+                light.ContainerOccluded = lightOccluded;
+            }
 
-                // We have to recursively scan for containers upwards in case of nested containers.
-                var tempParent = entity;
-                while (tempParent.TryGetContainer(out var container))
+            var childEnumerator = xform.ChildEnumerator;
+
+            // Try to avoid TryComp if we already know stuff is occluded.
+            if ((!spriteOccluded || !lightOccluded) && TryComp<ContainerManagerComponent>(entity, out var manager))
+            {
+                while (childEnumerator.MoveNext(out var child))
                 {
-                    if (container.OccludesLight)
+                    // Thank god it's by value and not by ref.
+                    var childSpriteOccluded = spriteOccluded;
+                    var childLightOccluded = lightOccluded;
+
+                    // We already know either sprite or light is not occluding so need to check container.
+                    if (manager.TryGetContainer(child.Value, out var container))
                     {
-                        light.ContainerOccluded = true;
-                        break;
+                        childSpriteOccluded = childSpriteOccluded || !container.ShowContents;
+                        childLightOccluded = childLightOccluded || container.OccludesLight;
                     }
 
-                    tempParent = container.Owner;
+                    UpdateEntity(child.Value, xformQuery.GetComponent(child.Value), xformQuery, pointQuery, spriteQuery, childSpriteOccluded, childLightOccluded);
+                }
+            }
+            else
+            {
+                while (childEnumerator.MoveNext(out var child))
+                {
+                    UpdateEntity(child.Value, xformQuery.GetComponent(child.Value), xformQuery, pointQuery, spriteQuery, spriteOccluded, lightOccluded);
                 }
             }
         }

Robust.Client/GameObjects/EntitySystems/DebugLightTreeSystem.cs

@@ -25,7 +25,7 @@ namespace Robust.Client.GameObjects
                 if (_enabled)
                 {
                     _lightOverlay = new DebugLightOverlay(
-                        IoCManager.Resolve<IEntityLookup>(),
+                        EntitySystem.Get<EntityLookupSystem>(),
                         IoCManager.Resolve<IEyeManager>(),
                         IoCManager.Resolve<IMapManager>(),
                         Get<RenderingTreeSystem>());
@@ -44,7 +44,7 @@ namespace Robust.Client.GameObjects
 
         private sealed class DebugLightOverlay : Overlay
         {
-            private IEntityLookup _lookup;
+            private EntityLookupSystem _lookup;
             private IEyeManager _eyeManager;
             private IMapManager _mapManager;
 
@@ -52,7 +52,7 @@ namespace Robust.Client.GameObjects
 
             public override OverlaySpace Space => OverlaySpace.WorldSpace;
 
-            public DebugLightOverlay(IEntityLookup lookup, IEyeManager eyeManager, IMapManager mapManager, RenderingTreeSystem tree)
+            public DebugLightOverlay(EntityLookupSystem lookup, IEyeManager eyeManager, IMapManager mapManager, RenderingTreeSystem tree)
             {
                 _lookup = lookup;
                 _eyeManager = eyeManager;
@@ -72,7 +72,7 @@ namespace Robust.Client.GameObjects
                 {
                     foreach (var light in tree.LightTree)
                     {
-                        var aabb = _lookup.GetWorldAabbFromEntity(light.Owner);
+                        var aabb = _lookup.GetWorldAABB(light.Owner);
                         if (!aabb.Intersects(worldBounds)) continue;
 
                         args.WorldHandle.DrawRect(aabb, Color.Green.WithAlpha(0.1f));

Robust.Client/GameObjects/EntitySystems/EffectSystem.cs

@@ -15,7 +15,7 @@ using Robust.Shared.Enums;
 
 namespace Robust.Client.GameObjects
 {
-    public class EffectSystem : EntitySystem
+    public sealed class EffectSystem : EntitySystem
     {
         [Dependency] private readonly IGameTiming gameTiming = default!;
         [Dependency] private readonly IResourceCache resourceCache = default!;
@@ -94,7 +94,7 @@ namespace Robust.Client.GameObjects
             }
         }
 
-        private class Effect
+        private sealed class Effect
         {
             /// <summary>
             /// Effect Sprite
@@ -323,7 +323,7 @@ namespace Robust.Client.GameObjects
         {
             private readonly IPlayerManager _playerManager;
 
-            public override OverlaySpace Space => OverlaySpace.WorldSpace;
+            public override OverlaySpace Space => OverlaySpace.WorldSpaceBelowFOV;
 
             private readonly ShaderInstance _unshadedShader;
             private readonly EffectSystem _owner;

Robust.Client/GameObjects/EntitySystems/EyeUpdateSystem.cs

@@ -20,7 +20,7 @@ namespace Robust.Client.GameObjects
     /// Updates the position of every Eye every frame, so that the camera follows the player around.
     /// </summary>
     [UsedImplicitly]
-    public class EyeUpdateSystem : EntitySystem
+    public sealed class EyeUpdateSystem : EntitySystem
     {
         /// <inheritdoc />
         public override void Initialize()

Robust.Client/GameObjects/EntitySystems/GridChunkBoundsDebugSystem.cs

@@ -10,7 +10,7 @@ using Robust.Shared.Utility;
 
 namespace Robust.Client.GameObjects
 {
-    public class GridChunkBoundsDebugSystem : EntitySystem
+    public sealed class GridChunkBoundsDebugSystem : EntitySystem
     {
         [Dependency] private readonly IEyeManager _eyeManager = default!;
         [Dependency] private readonly IMapManager _mapManager = default!;

Robust.Client/GameObjects/EntitySystems/InputSystem.cs

@@ -4,11 +4,15 @@ using Robust.Client.Input;
 using Robust.Client.Player;
 using Robust.Shared;
 using Robust.Shared.Configuration;
+using Robust.Shared.Console;
 using Robust.Shared.GameObjects;
 using Robust.Shared.Input;
 using Robust.Shared.IoC;
 using Robust.Shared.Log;
+using Robust.Shared.Map;
+using Robust.Shared.Maths;
 using Robust.Shared.Players;
+using Robust.Shared.Timing;
 using Robust.Shared.Utility;
 
 namespace Robust.Client.GameObjects
@@ -16,11 +20,13 @@ namespace Robust.Client.GameObjects
     /// <summary>
     ///     Client-side processing of all input commands through the simulation.
     /// </summary>
-    public class InputSystem : SharedInputSystem
+    public sealed class InputSystem : SharedInputSystem
     {
         [Dependency] private readonly IInputManager _inputManager = default!;
         [Dependency] private readonly IPlayerManager _playerManager = default!;
         [Dependency] private readonly IClientGameStateManager _stateManager = default!;
+        [Dependency] private readonly IConsoleHost _conHost = default!;
+        [Dependency] private readonly IGameTiming _timing = default!;
 
         private readonly IPlayerCommandStates _cmdStates = new PlayerCommandStates();
 
@@ -108,6 +114,43 @@ namespace Robust.Client.GameObjects
         public override void Initialize()
         {
             SubscribeLocalEvent<PlayerAttachSysMessage>(OnAttachedEntityChanged);
+
+            _conHost.RegisterCommand("incmd",
+                "Inserts an input command into the simulation",
+                "incmd <KeyFunction> <d|u KeyState> <wxPos> <wyPos>",
+                GenerateInputCommand);
+        }
+
+        public override void Shutdown()
+        {
+            base.Shutdown();
+
+            _conHost.UnregisterCommand("incmd");
+        }
+
+        private void GenerateInputCommand(IConsoleShell shell, string argstr, string[] args)
+        {
+            var localPlayer = _playerManager.LocalPlayer;
+            if(localPlayer is null)
+                return;
+
+            var pent = localPlayer.ControlledEntity;
+            if(pent is null)
+                return;
+
+            BoundKeyFunction keyFunction = new BoundKeyFunction(args[0]);
+            BoundKeyState state = args[1] == "u" ? BoundKeyState.Up: BoundKeyState.Down;
+
+            var pxform = Transform(pent.Value);
+            var wPos = pxform.WorldPosition + new Vector2(float.Parse(args[2]), float.Parse(args[3]));
+            var coords = EntityCoordinates.FromMap(EntityManager, pent.Value, new MapCoordinates(wPos, pxform.MapID));
+
+            var funcId = _inputManager.NetworkBindMap.KeyFunctionID(keyFunction);
+
+            var message = new FullInputCmdMessage(_timing.CurTick, _timing.TickFraction, funcId, state,
+                coords, new ScreenCoordinates(0, 0, default), EntityUid.Invalid);
+
+            HandleInputCommand(localPlayer.Session, keyFunction, message);
         }
 
         private void OnAttachedEntityChanged(PlayerAttachSysMessage message)
@@ -163,7 +206,7 @@ namespace Robust.Client.GameObjects
     /// <summary>
     ///     Entity system message that is raised when the player changes attached entities.
     /// </summary>
-    public class PlayerAttachSysMessage : EntityEventArgs
+    public sealed class PlayerAttachSysMessage : EntityEventArgs
     {
         /// <summary>
         ///     New entity the player is attached to.
@@ -180,7 +223,7 @@ namespace Robust.Client.GameObjects
         }
     }
 
-    public class PlayerAttachedEvent : EntityEventArgs
+    public sealed class PlayerAttachedEvent : EntityEventArgs
     {
         public PlayerAttachedEvent(EntityUid entity)
         {
@@ -190,7 +233,7 @@ namespace Robust.Client.GameObjects
         public EntityUid Entity { get; }
     }
 
-    public class PlayerDetachedEvent : EntityEventArgs
+    public sealed class PlayerDetachedEvent : EntityEventArgs
     {
         public PlayerDetachedEvent(EntityUid entity)
         {

Robust.Client/GameObjects/EntitySystems/MidiSystem.cs

@@ -4,7 +4,7 @@ using Robust.Shared.IoC;
 
 namespace Robust.Client.GameObjects
 {
-    public class MidiSystem : EntitySystem
+    public sealed class MidiSystem : EntitySystem
     {
         [Dependency] private readonly IMidiManager _midiManager = default!;
 

Robust.Client/GameObjects/EntitySystems/RenderingTreeSystem.cs

@@ -113,10 +113,18 @@ namespace Robust.Client.GameObjects
 
         private void AnythingMoved(ref MoveEvent args)
         {
-            AnythingMovedSubHandler(args.Sender);
+            var pointQuery = EntityManager.GetEntityQuery<PointLightComponent>();
+            var spriteQuery = EntityManager.GetEntityQuery<SpriteComponent>();
+            var xformQuery = EntityManager.GetEntityQuery<TransformComponent>();
+
+            AnythingMovedSubHandler(args.Sender, xformQuery, pointQuery, spriteQuery);
         }
 
-        private void AnythingMovedSubHandler(EntityUid uid, TransformComponent? xform = null)
+        private void AnythingMovedSubHandler(
+            EntityUid uid,
+            EntityQuery<TransformComponent> xformQuery,
+            EntityQuery<PointLightComponent> pointQuery,
+            EntityQuery<SpriteComponent> spriteQuery)
         {
             // To avoid doing redundant updates (and we don't need to update a grid's children ever)
             if (!_checkedChildren.Add(uid) || EntityManager.HasComponent<RenderingTreeComponent>(uid)) return;
@@ -125,17 +133,19 @@ namespace Robust.Client.GameObjects
             // WHATEVER YOU DO, DON'T REPLACE THIS WITH SPAMMING EVENTS UNLESS YOU HAVE A GUARANTEE IT WON'T LAG THE GC.
             // (Struct-based events ok though)
             // Ironically this was lagging the GC lolz
-            if (EntityManager.TryGetComponent(uid, out SpriteComponent? sprite))
+            if (spriteQuery.TryGetComponent(uid, out var sprite))
                 QueueSpriteUpdate(sprite);
 
-            if (EntityManager.TryGetComponent(uid, out PointLightComponent? light))
+            if (pointQuery.TryGetComponent(uid, out var light))
                 QueueLightUpdate(light);
 
-            if (!Resolve(uid, ref xform)) return;
+            if (!xformQuery.TryGetComponent(uid, out var xform)) return;
 
-            foreach (var child in xform.ChildEntities)
+            var childEnumerator = xform.ChildEnumerator;
+
+            while (childEnumerator.MoveNext(out var child))
             {
-                AnythingMovedSubHandler(child);
+                AnythingMovedSubHandler(child.Value, xformQuery, pointQuery, spriteQuery);
             }
         }
 
@@ -248,23 +258,21 @@ namespace Robust.Client.GameObjects
             EntityManager.EnsureComponent<RenderingTreeComponent>(_mapManager.GetGrid(gridId).GridEntityId);
         }
 
-        // TODO: Pass in TransformComponent directly: mainly interested in getting this shit working atm.
-        private RenderingTreeComponent? GetRenderTree(EntityUid entity)
+        private RenderingTreeComponent? GetRenderTree(EntityUid entity, EntityQuery<TransformComponent> xforms)
         {
+            var lookups = EntityManager.GetEntityQuery<RenderingTreeComponent>();
+
             if (!EntityManager.EntityExists(entity) ||
-                !EntityManager.TryGetComponent(entity, out TransformComponent? xform) ||
+                !xforms.TryGetComponent(entity, out var xform) ||
                 xform.MapID == MapId.Nullspace ||
-                EntityManager.HasComponent<RenderingTreeComponent>(entity)) return null;
+                lookups.HasComponent(entity)) return null;
 
             var parent = xform.ParentUid;
 
-            while (true)
+            while (parent.IsValid())
             {
-                if (!parent.IsValid())
-                    break;
-
-                if (EntityManager.TryGetComponent(parent, out RenderingTreeComponent? comp)) return comp;
-                parent = EntityManager.GetComponent<TransformComponent>(parent).ParentUid;
+                if (lookups.TryGetComponent(parent, out var comp)) return comp;
+                parent = xforms.GetComponent(parent).ParentUid;
             }
 
             return null;
@@ -279,6 +287,8 @@ namespace Robust.Client.GameObjects
         {
             _checkedChildren.Clear();
 
+            var xforms = EntityManager.GetEntityQuery<TransformComponent>();
+
             foreach (var sprite in _spriteQueue)
             {
                 sprite.TreeUpdateQueued = false;
@@ -289,9 +299,9 @@ namespace Robust.Client.GameObjects
                 }
 
                 var oldMapTree = sprite.RenderTree;
-                var newMapTree = GetRenderTree(sprite.Owner);
+                var newMapTree = GetRenderTree(sprite.Owner, xforms);
                 // TODO: Temp PVS guard
-                var xform = EntityManager.GetComponent<TransformComponent>(sprite.Owner);
+                var xform = xforms.GetComponent(sprite.Owner);
                 var (worldPos, worldRot) = xform.GetWorldPositionRotation();
 
                 if (float.IsNaN(worldPos.X) || float.IsNaN(worldPos.Y))
@@ -300,7 +310,7 @@ namespace Robust.Client.GameObjects
                     continue;
                 }
 
-                var aabb = SpriteAabbFunc(sprite, worldPos, worldRot);
+                var aabb = SpriteAabbFunc(sprite, worldPos, worldRot, xforms);
 
                 // If we're on a new map then clear the old one.
                 if (oldMapTree != newMapTree)
@@ -327,9 +337,9 @@ namespace Robust.Client.GameObjects
                 }
 
                 var oldMapTree = light.RenderTree;
-                var newMapTree = GetRenderTree(light.Owner);
+                var newMapTree = GetRenderTree(light.Owner, xforms);
                 // TODO: Temp PVS guard
-                var worldPos = EntityManager.GetComponent<TransformComponent>(light.Owner).WorldPosition;
+                var worldPos = xforms.GetComponent(light.Owner).WorldPosition;
 
                 if (float.IsNaN(worldPos.X) || float.IsNaN(worldPos.Y))
                 {
@@ -344,7 +354,7 @@ namespace Robust.Client.GameObjects
                     Logger.WarningS(LoggerSawmill, $"Light radius for {light.Owner} set above max radius of {MaxLightRadius}. This may lead to pop-in.");
                 }
 
-                var aabb = LightAabbFunc(light, worldPos);
+                var aabb = LightAabbFunc(light, worldPos, xforms);
 
                 // If we're on a new map then clear the old one.
                 if (oldMapTree != newMapTree)
@@ -366,69 +376,40 @@ namespace Robust.Client.GameObjects
 
         private Box2 SpriteAabbFunc(in SpriteComponent value)
         {
-            var xform = EntityManager.GetComponent<TransformComponent>(value.Owner);
+            var xforms = EntityManager.GetEntityQuery<TransformComponent>();
+            var xform = xforms.GetComponent(value.Owner);
             var (worldPos, worldRot) = xform.GetWorldPositionRotation();
-            var bounds = new Box2Rotated(value.CalculateBoundingBox(worldPos), worldRot, worldPos);
-            var tree = GetRenderTree(value.Owner);
 
-            if (tree == null)
-            {
-                return bounds.CalcBoundingBox();
-            }
-            else
-            {
-                return EntityManager.GetComponent<TransformComponent>(tree.Owner).InvWorldMatrix.TransformBox(bounds);
-            }
+            return SpriteAabbFunc(value, worldPos, worldRot, xforms);
         }
 
         private Box2 LightAabbFunc(in PointLightComponent value)
         {
-            var worldPos = EntityManager.GetComponent<TransformComponent>(value.Owner).WorldPosition;
-            var tree = GetRenderTree(value.Owner);
+            var xforms = EntityManager.GetEntityQuery<TransformComponent>();
+
+            var worldPos = xforms.GetComponent(value.Owner).WorldPosition;
+            var tree = GetRenderTree(value.Owner, xforms);
             var boxSize = value.Radius * 2;
 
-            Vector2 localPos;
-            if (tree == null)
-            {
-                localPos = worldPos;
-            }
-            else
-            {
-                // TODO: Need a way to just cache this InvWorldMatrix
-                localPos = EntityManager.GetComponent<TransformComponent>(tree.Owner).InvWorldMatrix.Transform(worldPos);
-            }
+            var localPos = tree == null ? worldPos : xforms.GetComponent(tree.Owner).InvWorldMatrix.Transform(worldPos);
             return Box2.CenteredAround(localPos, (boxSize, boxSize));
         }
 
-        private Box2 SpriteAabbFunc(SpriteComponent value, Vector2 worldPos, Angle worldRot)
+        private Box2 SpriteAabbFunc(SpriteComponent value, Vector2 worldPos, Angle worldRot, EntityQuery<TransformComponent> xforms)
         {
-            var bounds = new Box2Rotated(value.CalculateBoundingBox(worldPos), worldRot, worldPos);
-            var tree = GetRenderTree(value.Owner);
+            var bounds = value.CalculateRotatedBoundingBox(worldPos, worldRot);
+            var tree = GetRenderTree(value.Owner, xforms);
 
-            if (tree == null)
-            {
-                return bounds.CalcBoundingBox();
-            }
-            else
-            {
-                return EntityManager.GetComponent<TransformComponent>(tree.Owner).InvWorldMatrix.TransformBox(bounds);
-            }
+            return tree == null ? bounds.CalcBoundingBox() : xforms.GetComponent(tree.Owner).InvWorldMatrix.TransformBox(bounds);
         }
 
-        private Box2 LightAabbFunc(PointLightComponent value, Vector2 worldPos)
+        private Box2 LightAabbFunc(PointLightComponent value, Vector2 worldPos, EntityQuery<TransformComponent> xforms)
         {
             // Lights are circles so don't need entity's rotation
-            var tree = GetRenderTree(value.Owner);
+            var tree = GetRenderTree(value.Owner, xforms);
             var boxSize = value.Radius * 2;
 
-            Vector2 localPos;
-            if (tree == null)
-            {
-                localPos = worldPos;
-            } else
-            {
-                localPos = EntityManager.GetComponent<TransformComponent>(tree.Owner).InvWorldMatrix.Transform(worldPos);
-            }
+            var localPos = tree == null ? worldPos : xforms.GetComponent(tree.Owner).InvWorldMatrix.Transform(worldPos);
             return Box2.CenteredAround(localPos, (boxSize, boxSize));
         }
     }

Robust.Client/GameObjects/EntitySystems/SpriteSystem.Specifier.cs

@@ -0,0 +1,84 @@
+using System;
+using JetBrains.Annotations;
+using Robust.Client.Graphics;
+using Robust.Client.ResourceManagement;
+using Robust.Client.Utility;
+using Robust.Shared.GameObjects;
+using Robust.Shared.IoC;
+using Robust.Shared.Log;
+using Robust.Shared.Map;
+using Robust.Shared.Prototypes;
+using Robust.Shared.Utility;
+
+namespace Robust.Client.GameObjects;
+
+public sealed partial class SpriteSystem
+{
+    [Dependency] private readonly IPrototypeManager _proto = default!;
+    [Dependency] private readonly IResourceCache _resourceCache = default!;
+
+    [Pure]
+    public Texture Frame0(SpriteSpecifier specifier)
+    {
+        return RsiStateLike(specifier).Default;
+    }
+
+    [Pure]
+    public IRsiStateLike RsiStateLike(SpriteSpecifier specifier)
+    {
+        switch (specifier)
+        {
+            case SpriteSpecifier.Texture tex:
+                return tex.GetTexture(_resourceCache);
+
+            case SpriteSpecifier.Rsi rsi:
+                return GetState(rsi);
+
+            case SpriteSpecifier.EntityPrototype prototypeIcon:
+                if (!_proto.TryIndex<EntityPrototype>(prototypeIcon.EntityPrototypeId, out var prototype))
+                {
+                    Logger.Error("Failed to load PrototypeIcon {0}", prototypeIcon.EntityPrototypeId);
+                    return SpriteComponent.GetFallbackState(_resourceCache);
+                }
+
+                return SpriteComponent.GetPrototypeIcon(prototype, _resourceCache);
+
+            default:
+                throw new NotSupportedException();
+        }
+    }
+
+    [Pure]
+    public IRsiStateLike GetPrototypeIcon(EntityPrototype prototype, IResourceCache resourceCache)
+    {
+        var icon = IconComponent.GetPrototypeIcon(prototype, _resourceCache);
+        if (icon != null) return icon;
+
+        if (!prototype.Components.ContainsKey("Sprite"))
+        {
+            return SpriteComponent.GetFallbackState(resourceCache);
+        }
+
+        var dummy = Spawn(prototype.ID, MapCoordinates.Nullspace);
+        var spriteComponent = EnsureComp<SpriteComponent>(dummy);
+        var result = spriteComponent.Icon ?? SpriteComponent.GetFallbackState(resourceCache);
+        Del(dummy);
+
+        return result;
+    }
+
+    [Pure]
+    public RSI.State GetState(SpriteSpecifier.Rsi rsiSpecifier)
+    {
+        if (_resourceCache.TryGetResource<RSIResource>(
+                SharedSpriteComponent.TextureRoot / rsiSpecifier.RsiPath,
+                out var theRsi) &&
+            theRsi.RSI.TryGetState(rsiSpecifier.RsiState, out var state))
+        {
+            return state;
+        }
+
+        Logger.Error("Failed to load RSI {0}", rsiSpecifier.RsiPath);
+        return SpriteComponent.GetFallbackState(_resourceCache);
+    }
+}

Robust.Client/GameObjects/EntitySystems/SpriteSystem.cs

@@ -11,7 +11,7 @@ namespace Robust.Client.GameObjects
     /// Updates the layer animation for every visible sprite.
     /// </summary>
     [UsedImplicitly]
-    public class SpriteSystem : EntitySystem
+    public sealed partial class SpriteSystem : EntitySystem
     {
         [Dependency] private readonly IEyeManager _eyeManager = default!;
         [Dependency] private readonly RenderingTreeSystem _treeSystem = default!;
@@ -53,9 +53,11 @@ namespace Robust.Client.GameObjects
                 return;
             }
 
+            var xforms = EntityManager.GetEntityQuery<TransformComponent>();
+
             foreach (var comp in _treeSystem.GetRenderTrees(currentMap, pvsBounds))
             {
-                var bounds = EntityManager.GetComponent<TransformComponent>(comp.Owner).InvWorldMatrix.TransformBox(pvsBounds);
+                var bounds = xforms.GetComponent(comp.Owner).InvWorldMatrix.TransformBox(pvsBounds);
 
                 comp.SpriteTree.QueryAabb(ref frameTime, (ref float state, in SpriteComponent value) =>
                 {

Robust.Client/GameObjects/EntitySystems/VelocityDebugSystem.cs

@@ -8,7 +8,7 @@ using Robust.Shared.Maths;
 
 namespace Robust.Client.GameObjects
 {
-    public class VelocityDebugSystem : EntitySystem
+    public sealed class VelocityDebugSystem : EntitySystem
     {
         [Dependency] private readonly IEyeManager _eyeManager = default!;
         [Dependency] private readonly IPlayerManager _playerManager = default!;

Robust.Client/GameObjects/EntitySystems/VisualizerSystem.cs

@@ -0,0 +1,20 @@
+using Robust.Shared.GameObjects;
+
+namespace Robust.Client.GameObjects;
+
+/// <summary>
+///     An abstract entity system inheritor for systems that deal with
+///     appearance data, replacing <see cref="AppearanceVisualizer"/>.
+/// </summary>
+public abstract class VisualizerSystem<T> : EntitySystem
+    where T: Component
+{
+    public override void Initialize()
+    {
+        base.Initialize();
+
+        SubscribeLocalEvent<T, AppearanceChangeEvent>(OnAppearanceChange);
+    }
+
+    protected virtual void OnAppearanceChange(EntityUid uid, T component, ref AppearanceChangeEvent args) {}
+}

Robust.Client/GameStates/ClientGameStateManager.cs

@@ -7,7 +7,6 @@ using System.Linq;
 using JetBrains.Annotations;
 using Robust.Client.GameObjects;
 using Robust.Client.Input;
-using Robust.Client.Map;
 using Robust.Client.Player;
 using Robust.Client.Timing;
 using Robust.Shared;
@@ -29,7 +28,7 @@ namespace Robust.Client.GameStates
 {
     /// <inheritdoc />
     [UsedImplicitly]
-    public class ClientGameStateManager : IClientGameStateManager
+    public sealed class ClientGameStateManager : IClientGameStateManager
     {
         private GameStateProcessor _processor = default!;
 
@@ -46,11 +45,10 @@ namespace Robust.Client.GameStates
 
         [Dependency] private readonly IComponentFactory _compFactory = default!;
         [Dependency] private readonly IClientEntityManagerInternal _entities = default!;
-        [Dependency] private readonly IEntityLookup _lookup = default!;
         [Dependency] private readonly IPlayerManager _players = default!;
         [Dependency] private readonly IClientNetManager _network = default!;
         [Dependency] private readonly IBaseClient _client = default!;
-        [Dependency] private readonly IClientMapManager _mapManager = default!;
+        [Dependency] private readonly INetworkedMapManager _mapManager = default!;
         [Dependency] private readonly IClientGameTiming _timing = default!;
         [Dependency] private readonly INetConfigurationManager _config = default!;
         [Dependency] private readonly IEntitySystemManager _entitySystemManager = default!;
@@ -60,6 +58,8 @@ namespace Robust.Client.GameStates
         [Dependency] private readonly IRuntimeLog _runtimeLog = default!;
 #endif
 
+        private ISawmill _sawmill = default!;
+
         /// <inheritdoc />
         public int MinBufferSize => _processor.MinBufferSize;
 
@@ -87,6 +87,7 @@ namespace Robust.Client.GameStates
         /// <inheritdoc />
         public void Initialize()
         {
+            _sawmill = Logger.GetSawmill(CVars.NetPredict.Name);
             _processor = new GameStateProcessor(_timing);
 
             _network.RegisterNetMessage<MsgState>(HandleStateMessage);
@@ -144,7 +145,7 @@ namespace Robust.Client.GameStates
             _pendingInputs.Enqueue(message);
 
             _inputManager.NetworkBindMap.TryGetKeyFunction(message.InputFunctionId, out var boundFunc);
-            Logger.DebugS(CVars.NetPredict.Name,
+            _sawmill.Debug(
                 $"CL> SENT tick={_timing.CurTick}, sub={_timing.TickFraction}, seq={_nextInputCmdSeq}, func={boundFunc.FunctionName}, state={message.State}");
             _nextInputCmdSeq++;
         }
@@ -238,7 +239,7 @@ namespace Robust.Client.GameStates
 
                 if (_lastProcessedSeq < curState.LastProcessedInput)
                 {
-                    Logger.DebugS(CVars.NetPredict.Name, $"SV> RCV  tick={_timing.CurTick}, seq={_lastProcessedSeq}");
+                    _sawmill.Debug($"SV> RCV  tick={_timing.CurTick}, seq={_lastProcessedSeq}");
                     _lastProcessedSeq = curState.LastProcessedInput;
                 }
             }
@@ -257,8 +258,7 @@ namespace Robust.Client.GameStates
                 var inCmd = _pendingInputs.Dequeue();
 
                 _inputManager.NetworkBindMap.TryGetKeyFunction(inCmd.InputFunctionId, out var boundFunc);
-                Logger.DebugS(CVars.NetPredict.Name,
-                    $"SV>     seq={inCmd.InputSequence}, func={boundFunc.FunctionName}, state={inCmd.State}");
+                _sawmill.Debug($"SV>     seq={inCmd.InputSequence}, func={boundFunc.FunctionName}, state={inCmd.State}");
             }
 
             while (_pendingSystemMessages.Count > 0 && _pendingSystemMessages.Peek().sequence <= _lastProcessedSeq)
@@ -274,7 +274,7 @@ namespace Robust.Client.GameStates
 
                 if (_pendingInputs.Count > 0)
                 {
-                    Logger.DebugS(CVars.NetPredict.Name,  "CL> Predicted:");
+                    _sawmill.Debug("CL> Predicted:");
                 }
 
                 var pendingInputEnumerator = _pendingInputs.GetEnumerator();
@@ -299,7 +299,7 @@ namespace Robust.Client.GameStates
 
                         _inputManager.NetworkBindMap.TryGetKeyFunction(inputCmd.InputFunctionId, out var boundFunc);
 
-                        Logger.DebugS(CVars.NetPredict.Name,
+                        _sawmill.Debug(
                             $"    seq={inputCmd.InputSequence}, sub={inputCmd.SubTick}, dTick={tick}, func={boundFunc.FunctionName}, " +
                             $"state={inputCmd.State}");
 
@@ -331,8 +331,6 @@ namespace Robust.Client.GameStates
             }
 
             _entities.TickUpdate((float) _timing.TickPeriod.TotalSeconds, noPredictions: !IsPredictionEnabled);
-
-            _lookup.Update();
         }
 
         private void ResetPredictedEntities(GameTick curTick)
@@ -347,7 +345,11 @@ namespace Robust.Client.GameStates
                     continue;
                 }
 
-                Logger.DebugS(CVars.NetPredict.Name, $"Entity {entity} was made dirty.");
+                // Check log level first to avoid the string alloc.
+                if (_sawmill.Level <= LogLevel.Debug)
+                {
+                    _sawmill.Debug($"Entity {entity} was made dirty.");
+                }
 
                 if (!_processor.TryGetLastServerStates(entity, out var last))
                 {
@@ -365,7 +367,7 @@ namespace Robust.Client.GameStates
                         continue;
                     }
 
-                    Logger.DebugS(CVars.NetPredict.Name, $"  And also its component {comp.GetType()}");
+                    _sawmill.Debug($"  And also its component {comp.GetType()}");
                     // TODO: Handle interpolation.
                     var handleState = new ComponentHandleState(compState, null);
                     _entities.EventBus.RaiseComponentEvent(comp, ref handleState);
@@ -632,7 +634,7 @@ namespace Robust.Client.GameStates
         }
     }
 
-    public class GameStateAppliedArgs : EventArgs
+    public sealed class GameStateAppliedArgs : EventArgs
     {
         public GameState AppliedState { get; }
 

Robust.Client/GameStates/GameStateProcessor.cs

@@ -10,7 +10,7 @@ using Robust.Shared.Utility;
 namespace Robust.Client.GameStates
 {
     /// <inheritdoc />
-    internal class GameStateProcessor : IGameStateProcessor
+    internal sealed class GameStateProcessor : IGameStateProcessor
     {
         private readonly IGameTiming _timing;
 

Robust.Client/GameStates/NetEntityOverlay.cs

@@ -19,7 +19,7 @@ namespace Robust.Client.GameStates
     /// A network entity report that lists all entities as they are updated through game states.
     /// https://developer.valvesoftware.com/wiki/Networking_Entities#cl_entityreport
     /// </summary>
-    class NetEntityOverlay : Overlay
+    sealed class NetEntityOverlay : Overlay
     {
         [Dependency] private readonly IGameTiming _gameTiming = default!;
         [Dependency] private readonly IClientNetManager _netManager = default!;
@@ -244,7 +244,7 @@ namespace Robust.Client.GameStates
             }
         }
 
-        private class NetEntityReportCommand : IConsoleCommand
+        private sealed class NetEntityReportCommand : IConsoleCommand
         {
             public string Command => "net_entityreport";
             public string Help => "net_entityreport <0|1>";

Robust.Client/GameStates/NetGraphOverlay.cs

@@ -16,7 +16,7 @@ namespace Robust.Client.GameStates
     /// <summary>
     ///     Visual debug overlay for the network diagnostic graph.
     /// </summary>
-    internal class NetGraphOverlay : Overlay
+    internal sealed class NetGraphOverlay : Overlay
     {
         [Dependency] private readonly IGameTiming _gameTiming = default!;
         [Dependency] private readonly IClientNetManager _netManager = default!;
@@ -239,7 +239,7 @@ namespace Robust.Client.GameStates
             base.DisposeBehavior();
         }
 
-        private class NetShowGraphCommand : IConsoleCommand
+        private sealed class NetShowGraphCommand : IConsoleCommand
         {
             public string Command => "net_graph";
             public string Help => "net_graph <0|1>";
@@ -275,7 +275,7 @@ namespace Robust.Client.GameStates
             }
         }
 
-        private class NetWatchEntCommand : IConsoleCommand
+        private sealed class NetWatchEntCommand : IConsoleCommand
         {
             public string Command => "net_watchent";
             public string Help => "net_watchent <0|EntityUid>";

Robust.Client/GameStates/NetInterpOverlay.cs

@@ -11,7 +11,7 @@ using Robust.Shared.Timing;
 
 namespace Robust.Client.GameStates
 {
-    internal class NetInterpOverlay : Overlay
+    internal sealed class NetInterpOverlay : Overlay
     {
         [Dependency] private readonly IEntityManager _entityManager = default!;
         [Dependency] private readonly IEyeManager _eyeManager = default!;
@@ -38,7 +38,7 @@ namespace Robust.Client.GameStates
                 var transform = _entityManager.GetComponent<TransformComponent>(boundingBox.Owner);
 
                 // if not on the same map, continue
-                if (transform.MapID != _eyeManager.CurrentMap || boundingBox.Owner.IsInContainer())
+                if (transform.MapID != _eyeManager.CurrentMap || boundingBox.Owner.IsInContainer(_entityManager))
                     continue;
 
                 // This entity isn't lerping, no need to draw debug info for it
@@ -65,7 +65,7 @@ namespace Robust.Client.GameStates
             }
         }
 
-        private class NetShowInterpCommand : IConsoleCommand
+        private sealed class NetShowInterpCommand : IConsoleCommand
         {
             public string Command => "net_draw_interp";
             public string Help => "net_draw_interp <0|1>";

Robust.Client/Graphics/Audio/ClydeAudio.cs

@@ -18,7 +18,7 @@ using Vector2 = Robust.Shared.Maths.Vector2;
 
 namespace Robust.Client.Graphics.Audio
 {
-    internal partial class ClydeAudio : IClydeAudio, IClydeAudioInternal
+    internal sealed partial class ClydeAudio : IClydeAudio, IClydeAudioInternal
     {
         private ALDevice _openALDevice;
         private ALContext _openALContext;
@@ -224,7 +224,7 @@ namespace Robust.Client.Graphics.Audio
                 _openALSawmill.Error("Failed to generate source. Too many simultaneous audio streams?");
                 return null;
             }
-            
+
             // ReSharper disable once PossibleInvalidOperationException
             // TODO: This really shouldn't be indexing based on the ClydeHandle...
             AL.Source(source, ALSourcei.Buffer, _audioSampleBuffers[(int) stream.ClydeHandle!.Value.Value].BufferHandle);

Robust.Client/Graphics/Audio/DummyAudioSource.cs

@@ -18,6 +18,7 @@ namespace Robust.Client.Graphics.Audio
     /// <summary>
     ///     Hey look, it's ClydeAudio.AudioSource's evil twin brother!
     /// </summary>
+    [Virtual]
     internal class DummyAudioSource : IClydeAudioSource
     {
         public static DummyAudioSource Instance { get; } = new();

Robust.Client/Graphics/ClientEye/Eye.cs

@@ -7,6 +7,7 @@ using Robust.Shared.ViewVariables;
 namespace Robust.Client.Graphics
 {
     /// <inheritdoc />
+    [Virtual]
     public class Eye : IEye
     {
         private Vector2 _scale = Vector2.One/2f;

Robust.Client/Graphics/ClientEye/EyeManager.cs

@@ -153,7 +153,7 @@ namespace Robust.Client.Graphics
         }
     }
 
-    public class CurrentEyeChangedEvent : EntityEventArgs
+    public sealed class CurrentEyeChangedEvent : EntityEventArgs
     {
         public IEye? Old { get; }
         public IEye New { get; }

Robust.Client/Graphics/ClientEye/FixedEye.cs

@@ -3,7 +3,7 @@
     /// <summary>
     ///     A fixed eye is an eye which is fixed to one point, its position.
     /// </summary>
-    public class FixedEye : Eye
+    public sealed class FixedEye : Eye
     {
     }
 }

Robust.Client/Graphics/Clyde/Clyde.GridRendering.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Buffers;
 using System.Collections.Generic;
 using System.Diagnostics;
@@ -18,8 +18,8 @@ namespace Robust.Client.Graphics.Clyde
         private readonly Dictionary<GridId, Dictionary<Vector2i, MapChunkData>> _mapChunkData =
             new();
 
-        private int _verticesPerChunk(IMapChunk chunk) => chunk.ChunkSize * chunk.ChunkSize * 4;
-        private int _indicesPerChunk(IMapChunk chunk) => chunk.ChunkSize * chunk.ChunkSize * GetQuadBatchIndexCount();
+        private int _verticesPerChunk(MapChunk chunk) => chunk.ChunkSize * chunk.ChunkSize * 4;
+        private int _indicesPerChunk(MapChunk chunk) => chunk.ChunkSize * chunk.ChunkSize * GetQuadBatchIndexCount();
 
         private void _drawGrids(Viewport viewport, Box2Rotated worldBounds, IEye eye)
         {
@@ -78,7 +78,7 @@ namespace Robust.Client.Graphics.Clyde
             }
         }
 
-        private void _updateChunkMesh(IMapGrid grid, IMapChunk chunk)
+        private void _updateChunkMesh(IMapGrid grid, MapChunk chunk)
         {
             var data = _mapChunkData[grid.Index];
 
@@ -91,25 +91,36 @@ namespace Robust.Client.Graphics.Clyde
             Span<Vertex2D> vertexBuffer = stackalloc Vertex2D[_verticesPerChunk(chunk)];
 
             var i = 0;
-            foreach (var tile in chunk)
+            var cSz = grid.ChunkSize;
+            var cScaled = chunk.Indices * cSz;
+            for (ushort x = 0; x < cSz; x++)
             {
-                var regionMaybe = _tileDefinitionManager.TileAtlasRegion(tile.Tile);
-                if (regionMaybe == null)
+                for (ushort y = 0; y < cSz; y++)
                 {
-                    continue;
+                    var tile = chunk.GetTile(x, y);
+                    if (tile.IsEmpty)
+                        continue;
+
+                    var regionMaybe = _tileDefinitionManager.TileAtlasRegion(tile.TypeId);
+                    if (regionMaybe == null)
+                    {
+                        continue;
+                    }
+
+                    var region = regionMaybe.Value;
+                    var gx = x + cScaled.X;
+                    var gy = y + cScaled.Y;
+
+                    var vIdx = i * 4;
+                    vertexBuffer[vIdx + 0] = new Vertex2D(gx, gy, region.Left, region.Bottom);
+                    vertexBuffer[vIdx + 1] = new Vertex2D(gx + 1, gy, region.Right, region.Bottom);
+                    vertexBuffer[vIdx + 2] = new Vertex2D(gx + 1, gy + 1, region.Right, region.Top);
+                    vertexBuffer[vIdx + 3] = new Vertex2D(gx, gy + 1, region.Left, region.Top);
+                    var nIdx = i * GetQuadBatchIndexCount();
+                    var tIdx = (ushort)(i * 4);
+                    QuadBatchIndexWrite(indexBuffer, ref nIdx, tIdx);
+                    i += 1;
                 }
-
-                var region = regionMaybe.Value;
-
-                var vIdx = i * 4;
-                vertexBuffer[vIdx + 0] = new Vertex2D(tile.X, tile.Y, region.Left, region.Bottom);
-                vertexBuffer[vIdx + 1] = new Vertex2D(tile.X + 1, tile.Y, region.Right, region.Bottom);
-                vertexBuffer[vIdx + 2] = new Vertex2D(tile.X + 1, tile.Y + 1, region.Right, region.Top);
-                vertexBuffer[vIdx + 3] = new Vertex2D(tile.X, tile.Y + 1, region.Left, region.Top);
-                var nIdx = i * GetQuadBatchIndexCount();
-                var tIdx = (ushort) (i * 4);
-                QuadBatchIndexWrite(indexBuffer, ref nIdx, tIdx);
-                i += 1;
             }
 
             GL.BindVertexArray(datum.VAO);
@@ -122,7 +133,7 @@ namespace Robust.Client.Graphics.Clyde
             datum.TileCount = i;
         }
 
-        private MapChunkData _initChunkBuffers(IMapGrid grid, IMapChunk chunk)
+        private MapChunkData _initChunkBuffers(IMapGrid grid, MapChunk chunk)
         {
             var vao = GenVertexArray();
             BindVertexArray(vao);
@@ -159,7 +170,7 @@ namespace Robust.Client.Graphics.Clyde
             return datum;
         }
 
-        private bool _isChunkDirty(IMapGrid grid, IMapChunk chunk)
+        private bool _isChunkDirty(IMapGrid grid, MapChunk chunk)
         {
             var data = _mapChunkData[grid.Index];
             return !data.TryGetValue(chunk.Indices, out var datum) || datum.Dirty;
@@ -214,7 +225,7 @@ namespace Robust.Client.Graphics.Clyde
             _mapChunkData.Remove(gridId);
         }
 
-        private class MapChunkData
+        private sealed class MapChunkData
         {
             public bool Dirty;
             public readonly uint VAO;

Robust.Client/Graphics/Clyde/Clyde.HLR.cs

@@ -24,11 +24,17 @@ namespace Robust.Client.Graphics.Clyde
     {
         public ClydeDebugLayers DebugLayers { get; set; }
 
-        private readonly RefList<(SpriteComponent sprite, Matrix3 worldMatrix, Angle worldRotation, float yWorldPos)>
+        private readonly RefList<(SpriteComponent sprite, Vector2 worldPos, Angle worldRotation, Box2 spriteScreenBB)>
             _drawingSpriteList
                 =
                 new();
 
+        // TODO allow this scale to be passed with PostShader as variable
+        /// <summary>
+        ///     Some shaders that enlarge the final sprite, like emission or highlight effects, need to use a slightly larger render target.
+        /// </summary>
+        public static float PostShadeScale = 1.25f;
+
         public void Render()
         {
             CheckTransferringScreenshots();
@@ -217,9 +223,8 @@ namespace Robust.Client.Graphics.Clyde
             RenderOverlays(viewport, OverlaySpace.WorldSpaceBelowEntities, worldAABB, worldBounds);
 
             var screenSize = viewport.Size;
-            eye.GetViewMatrix(out var eyeMatrix, eye.Scale);
 
-            ProcessSpriteEntities(mapId, eyeMatrix, worldBounds, _drawingSpriteList);
+            ProcessSpriteEntities(mapId, viewport, eye, worldBounds, _drawingSpriteList);
 
             var worldOverlays = new List<Overlay>();
 
@@ -276,30 +281,12 @@ namespace Robust.Client.Graphics.Clyde
                     break;
                 }
 
-                var matrix = entry.worldMatrix;
-                var worldPosition = new Vector2(matrix.R0C2, matrix.R1C2);
-
                 RenderTexture? entityPostRenderTarget = null;
                 Vector2i roundedPos = default;
                 if (entry.sprite.PostShader != null)
                 {
-                    // calculate world bounding box
-                    var spriteBB = entry.sprite.CalculateBoundingBox(worldPosition);
-                    var spriteLB = spriteBB.BottomLeft;
-                    var spriteRT = spriteBB.TopRight;
-
-                    // finally we can calculate screen bounding in pixels
-                    var screenLB = viewport.WorldToLocal(spriteLB);
-                    var screenRT = viewport.WorldToLocal(spriteRT);
-
-                    // we need to scale RT a for effects like emission or highlight
-                    // scale can be passed with PostShader as variable in future
-                    var postShadeScale = 1.25f;
-                    var screenSpriteSize = (Vector2i) ((screenRT - screenLB) * postShadeScale).Rounded();
-
-                    // Rotate the vector by the eye angle, otherwise the bounding box will be incorrect
-                    screenSpriteSize = (Vector2i) eye.Rotation.RotateVec(screenSpriteSize).Rounded();
-                    screenSpriteSize.Y = -screenSpriteSize.Y;
+                    // get the size of the sprite on screen, scaled slightly to allow for shaders that increase the final sprite size.
+                    var screenSpriteSize = (Vector2i) (entry.spriteScreenBB.Size * PostShadeScale).Rounded();
 
                     // I'm not 100% sure why it works, but without it post-shader
                     // can be lower or upper by 1px than original sprite depending on sprite rotation or scale
@@ -322,16 +309,14 @@ namespace Robust.Client.Graphics.Clyde
                         // Calculate viewport so that the entity thinks it's drawing to the same position,
                         // which is necessary for light application,
                         // but it's ACTUALLY drawing into the center of the render target.
-                        var spritePos = spriteBB.Center;
-                        var screenPos = viewport.WorldToLocal(spritePos);
-                        var (roundedX, roundedY) = roundedPos = (Vector2i) screenPos;
-                        var flippedPos = new Vector2i(roundedX, screenSize.Y - roundedY);
+                        roundedPos = (Vector2i) entry.spriteScreenBB.Center;
+                        var flippedPos = new Vector2i(roundedPos.X, screenSize.Y - roundedPos.Y);
                         flippedPos -= entityPostRenderTarget.Size / 2;
                         _renderHandle.Viewport(Box2i.FromDimensions(-flippedPos, screenSize));
                     }
                 }
 
-                entry.sprite.Render(_renderHandle.DrawingHandleWorld, eye.Rotation, in entry.worldRotation, in worldPosition);
+                entry.sprite.Render(_renderHandle.DrawingHandleWorld, eye.Rotation, in entry.worldRotation, in entry.worldPos);
 
                 if (entry.sprite.PostShader != null && entityPostRenderTarget != null)
                 {
@@ -369,28 +354,37 @@ namespace Robust.Client.Graphics.Clyde
         }
 
         [MethodImpl(MethodImplOptions.NoInlining)]
-        private void ProcessSpriteEntities(MapId map, Matrix3 eyeMatrix, Box2Rotated worldBounds,
-            RefList<(SpriteComponent sprite, Matrix3 matrix, Angle worldRot, float yWorldPos)> list)
+        private void ProcessSpriteEntities(MapId map, Viewport view, IEye eye, Box2Rotated worldBounds,
+            RefList<(SpriteComponent sprite, Vector2 worldPos, Angle worldRot, Box2 spriteScreenBB)> list)
         {
+            var xforms = _entityManager.GetEntityQuery<TransformComponent>();
+
+            // Construct a matrix equivalent for Viewport.WorldToLocal()
+            eye.GetViewMatrix(out var viewMatrix, view.RenderScale);
+            var uiProjmatrix = Matrix3.Identity;
+            uiProjmatrix.R0C0 = EyeManager.PixelsPerMeter;
+            uiProjmatrix.R1C1 = -EyeManager.PixelsPerMeter;
+            uiProjmatrix.R0C2 = view.Size.X / 2f;
+            uiProjmatrix.R1C2 = view.Size.Y / 2f;
+            var worldToLocal = viewMatrix * uiProjmatrix;
+
             foreach (var comp in _entitySystemManager.GetEntitySystem<RenderingTreeSystem>().GetRenderTrees(map, worldBounds))
             {
-                var bounds = _entityManager.GetComponent<TransformComponent>(comp.Owner).InvWorldMatrix.TransformBox(worldBounds);
+                var bounds = xforms.GetComponent(comp.Owner).InvWorldMatrix.TransformBox(worldBounds);
 
                 comp.SpriteTree.QueryAabb(ref list, (
-                    ref RefList<(SpriteComponent sprite, Matrix3 matrix, Angle worldRot, float yWorldPos)> state,
+                    ref RefList<(SpriteComponent sprite, Vector2 worldPos, Angle worldRot, Box2 spriteScreenBB)> state,
                     in SpriteComponent value) =>
                 {
                     var entity = value.Owner;
-                    var transform = _entityManager.GetComponent<TransformComponent>(entity);
+                    var transform = xforms.GetComponent(entity);
 
                     ref var entry = ref state.AllocAdd();
                     entry.sprite = value;
-                    entry.worldRot = transform.WorldRotation;
-                    entry.matrix = transform.WorldMatrix;
-                    var eyePos = eyeMatrix.Transform(new Vector2(entry.matrix.R0C2, entry.matrix.R1C2));
-                    // Didn't use the bounds from the query as that has to be re-calculated (and is probably more expensive than this).
-                    var bounds = value.CalculateBoundingBox(eyePos);
-                    entry.yWorldPos = eyePos.Y - bounds.Extents.Y;
+                    (entry.worldPos, entry.worldRot) = transform.GetWorldPositionRotation();
+
+                    var spriteWorldBB = value.CalculateRotatedBoundingBox(entry.worldPos, entry.worldRot, eye);
+                    entry.spriteScreenBB = worldToLocal.TransformBox(spriteWorldBB);
                     return true;
 
                 }, bounds, true);

Robust.Client/Graphics/Clyde/Clyde.Helpers.cs

@@ -62,7 +62,7 @@ namespace Robust.Client.Graphics.Clyde
                 PixelInternalFormat.Srgb8Alpha8 => 4,
                 PixelInternalFormat.R11fG11fB10f => 4,
                 PixelInternalFormat.R32f => 4,
-                PixelInternalFormat.Rg32f => 4,
+                PixelInternalFormat.Rg32f => 8,
                 PixelInternalFormat.R8 => 1,
                 _ => 0
             };

Robust.Client/Graphics/Clyde/Clyde.LightRendering.cs

@@ -514,13 +514,14 @@ namespace Robust.Client.Graphics.Clyde
             var enlargedBounds = worldAABB.Enlarged(renderingTreeSystem.MaxLightRadius);
 
             // Use worldbounds for this one as we only care if the light intersects our actual bounds
-            var state = (this, worldAABB, count: 0);
+            var state = (this, worldAABB, count: 0, shadowCastingCount: 0);
+            var xforms = _entityManager.GetEntityQuery<TransformComponent>();
 
             foreach (var comp in renderingTreeSystem.GetRenderTrees(map, enlargedBounds))
             {
-                var bounds = _entityManager.GetComponent<TransformComponent>(comp.Owner).InvWorldMatrix.TransformBox(worldBounds);
+                var bounds = xforms.GetComponent(comp.Owner).InvWorldMatrix.TransformBox(worldBounds);
 
-                comp.LightTree.QueryAabb(ref state, (ref (Clyde clyde, Box2 worldAABB, int count) state, in PointLightComponent light) =>
+                comp.LightTree.QueryAabb(ref state, (ref (Clyde clyde, Box2 worldAABB, int count, int shadowCastingCount) state, in PointLightComponent light) =>
                 {
                     if (state.count >= LightsToRenderListSize)
                     {
@@ -528,7 +529,7 @@ namespace Robust.Client.Graphics.Clyde
                         return false;
                     }
 
-                    var transform = _entityManager.GetComponent<TransformComponent>(light.Owner);
+                    var transform = xforms.GetComponent(light.Owner);
 
                     if (float.IsNaN(transform.LocalPosition.X) || float.IsNaN(transform.LocalPosition.Y)) return true;
 
@@ -542,6 +543,9 @@ namespace Robust.Client.Graphics.Clyde
                         return true;
                     }
 
+                    // If the light is a shadow casting light, keep a separate track of that
+                    if (light.CastShadows) state.shadowCastingCount++;
+
                     float distanceSquared = (state.worldAABB.Center - lightPos).LengthSquared;
                     state.clyde._lightsToRenderList[state.count++] = (light, lightPos, distanceSquared);
 
@@ -549,17 +553,29 @@ namespace Robust.Client.Graphics.Clyde
                 }, bounds);
             }
 
-            if (state.count > _maxLightsPerScene)
+            if (state.shadowCastingCount > _maxLightsPerScene)
             {
-                // There are too many lights to fit in the scene.
+                // There are too many lights casting shadows to fit in the scene.
                 // This check must occur before occluder expansion, or else bad things happen.
-                // Sort lights by distance.
+
+                // First, partition the array based on whether the lights are shadow casting or not
+                // (non shadow casting lights should be the first partition, shadow casting lights the second)
                 Array.Sort(_lightsToRenderList, 0, state.count, Comparer<(PointLightComponent light, Vector2 pos, float distanceSquared)>.Create((x, y) =>
+                {
+                    if (x.light.CastShadows && !y.light.CastShadows) return 1;
+                    else if (!x.light.CastShadows && y.light.CastShadows) return -1;
+                    else return 0;
+                }));
+
+                // Next, sort just the shadow casting lights by distance.
+                Array.Sort(_lightsToRenderList, state.count - state.shadowCastingCount, state.shadowCastingCount, Comparer<(PointLightComponent light, Vector2 pos, float distanceSquared)>.Create((x, y) =>
                 {
                     return x.distanceSquared.CompareTo(y.distanceSquared);
                 }));
-                // Then effectively delete the furthest lights.
-                state.count = _maxLightsPerScene;
+
+                // Then effectively delete the furthest lights, by setting the end of the array to exclude N
+                // number of shadow casting lights (where N is the number above the max number per scene.)
+                state.count -= state.shadowCastingCount - _maxLightsPerScene;
             }
 
             // When culling occluders later, we can't just remove any occluders outside the worldBounds.
@@ -871,21 +887,24 @@ namespace Robust.Client.Graphics.Clyde
                 var ii = 0;
                 var imi = 0;
 
+                var xforms = _entityManager.GetEntityQuery<TransformComponent>();
+
                 foreach (var comp in occluderSystem.GetOccluderTrees(map, expandedBounds))
                 {
-                    var treeBounds = _entityManager.GetComponent<TransformComponent>(comp.Owner).InvWorldMatrix.TransformBox(expandedBounds);
+                    var treeBounds = xforms.GetComponent(comp.Owner).InvWorldMatrix.TransformBox(expandedBounds);
 
                     comp.Tree.QueryAabb((in OccluderComponent sOccluder) =>
                     {
-                        var occluder = (ClientOccluderComponent)sOccluder;
-                        var transform = _entityManager.GetComponent<TransformComponent>(occluder.Owner);
-                        if (!occluder.Enabled)
+                        var transform = xforms.GetComponent(sOccluder.Owner);
+                        if (!sOccluder.Enabled)
                         {
                             return true;
                         }
 
+                        var occluder = (ClientOccluderComponent)sOccluder;
+
                         var worldTransform = transform.WorldMatrix;
-                        var box = occluder.BoundingBox;
+                        var box = sOccluder.BoundingBox;
 
                         var tl = worldTransform.Transform(box.TopLeft);
                         var tr = worldTransform.Transform(box.TopRight);

Robust.Client/Graphics/Clyde/Clyde.Rendering.cs

@@ -994,9 +994,9 @@ namespace Robust.Client.Graphics.Clyde
 
         private sealed class SpriteDrawingOrderComparer : IComparer<int>
         {
-            private readonly RefList<(SpriteComponent, Matrix3, Angle, float)> _drawList;
+            private readonly RefList<(SpriteComponent, Vector2, Angle, Box2)> _drawList;
 
-            public SpriteDrawingOrderComparer(RefList<(SpriteComponent, Matrix3, Angle, float)> drawList)
+            public SpriteDrawingOrderComparer(RefList<(SpriteComponent, Vector2, Angle, Box2)> drawList)
             {
                 _drawList = drawList;
             }
@@ -1019,7 +1019,8 @@ namespace Robust.Client.Graphics.Clyde
                     return cmp;
                 }
 
-                cmp = _drawList[y].Item4.CompareTo(_drawList[x].Item4);
+                // compare the top of the sprite's BB for y-sorting. Because screen coordinates are flipped, the "top" of the BB is actually the "bottom".
+                cmp = _drawList[x].Item4.Top.CompareTo(_drawList[y].Item4.Top);
 
                 if (cmp != 0)
                 {

Robust.Client/Graphics/Clyde/Clyde.Shaders.cs

@@ -34,7 +34,7 @@ namespace Robust.Client.Graphics.Clyde
 
         private readonly ConcurrentQueue<ClydeHandle> _deadShaderInstances = new();
 
-        private class LoadedShader
+        private sealed class LoadedShader
         {
             public GLShaderProgram Program = default!;
             public bool HasLighting = true;
@@ -42,7 +42,7 @@ namespace Robust.Client.Graphics.Clyde
             public string? Name;
         }
 
-        private class LoadedShaderInstance
+        private sealed class LoadedShaderInstance
         {
             public ClydeHandle ShaderHandle;
 

Robust.Client/Graphics/Clyde/Clyde.Viewport.cs

@@ -144,7 +144,7 @@ namespace Robust.Client.Graphics.Clyde
                 if (Eye == null)
                     return default;
 
-                var eye = (IEye) Eye;
+                var eye = Eye;
                 var newPoint = point;
 
                 eye.GetViewMatrix(out var viewMatrix, RenderScale);

Robust.Client/Graphics/Clyde/ClydeHeadless.cs

@@ -246,7 +246,7 @@ namespace Robust.Client.Graphics.Clyde
             // Nada.
         }
 
-        private class DummyCursor : ICursor
+        private sealed class DummyCursor : ICursor
         {
             public void Dispose()
             {
@@ -254,6 +254,7 @@ namespace Robust.Client.Graphics.Clyde
             }
         }
 
+        [Virtual]
         private class DummyAudioSource : IClydeAudioSource
         {
             public static DummyAudioSource Instance { get; } = new();

Robust.Client/Graphics/Clyde/GLObjects/Clyde.Buffer.cs

@@ -11,6 +11,7 @@ namespace Robust.Client.Graphics.Clyde
         /// <summary>
         ///     Represents an OpenGL buffer object.
         /// </summary>
+        [Virtual]
         private class GLBuffer
         {
             private readonly Clyde _clyde;
@@ -178,7 +179,7 @@ namespace Robust.Client.Graphics.Clyde
         ///     Subtype of buffers so that we can have a generic constructor.
         ///     Functionally equivalent to <see cref="GLBuffer"/> otherwise.
         /// </summary>
-        private class GLBuffer<T> : GLBuffer where T : unmanaged
+        private sealed class GLBuffer<T> : GLBuffer where T : unmanaged
         {
             public GLBuffer(Clyde clyde, BufferTarget type, BufferUsageHint usage, Span<T> initialize,
                 string? name = null)

Robust.Client/Graphics/Clyde/GLObjects/Clyde.Shader.cs

@@ -4,7 +4,7 @@ namespace Robust.Client.Graphics.Clyde
 {
     internal partial class Clyde
     {
-        private class GLShader
+        private sealed class GLShader
         {
             private readonly Clyde _clyde;
 

Robust.Client/Graphics/Clyde/GLObjects/Clyde.ShaderProgram.cs

@@ -14,7 +14,7 @@ namespace Robust.Client.Graphics.Clyde
         ///     You've been warned:
         ///     using things like <see cref="SetUniformTexture" /> if this buffer isn't bound WILL mess things up!
         /// </summary>
-        private class GLShaderProgram
+        private sealed class GLShaderProgram
         {
             private readonly sbyte?[] _uniformIntCache = new sbyte?[UniCount];
             private readonly Dictionary<string, int> _uniformCache = new();

Robust.Client/Graphics/Clyde/GLObjects/Clyde.UniformBuffer.cs

@@ -20,7 +20,7 @@ namespace Robust.Client.Graphics.Clyde
         /// <summary>
         ///     Represents some set of uniforms that can be backed by a uniform buffer or by regular uniforms.
         /// </summary>
-        private class GLUniformBuffer<T> where T : unmanaged, IAppliableUniformSet
+        private sealed class GLUniformBuffer<T> where T : unmanaged, IAppliableUniformSet
         {
             private readonly Clyde _clyde;
             private readonly int _index;

Robust.Client/Graphics/Clyde/ShaderCompilationException.cs

@@ -6,6 +6,7 @@ namespace Robust.Client.Graphics.Clyde
 {
     [Serializable]
     [PublicAPI]
+    [Virtual]
     internal class ShaderCompilationException : Exception
     {
         public ShaderCompilationException()

Robust.Client/Graphics/Clyde/Windowing/Glfw.cs

@@ -104,6 +104,7 @@ namespace Robust.Client.Graphics.Clyde
             }
 
             [Serializable]
+            [Virtual]
             public class GlfwException : Exception
             {
                 public GlfwException()

Robust.Client/Graphics/Drawing/StyleBoxEmpty.cs

@@ -2,7 +2,7 @@ using Robust.Shared.Maths;
 
 namespace Robust.Client.Graphics
 {
-    public class StyleBoxEmpty : StyleBox
+    public sealed class StyleBoxEmpty : StyleBox
     {
         protected override void DoDraw(DrawingHandleScreen handle, UIBox2 box)
         {

Robust.Client/Graphics/Drawing/StyleBoxFlat.cs

@@ -3,7 +3,7 @@ using Robust.Shared.Maths;
 
 namespace Robust.Client.Graphics
 {
-    public class StyleBoxFlat : StyleBox
+    public sealed class StyleBoxFlat : StyleBox
     {
         public Color BackgroundColor { get; set; }
         public Color BorderColor { get; set; }