Update README.md to include project description, developer documentation links, and license information.

tests/MrGameEng.Core.Tests/SceneSystemsTests.cs

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+using Friflo.Engine.ECS;
+using Friflo.Engine.ECS.Systems;
+using MrGameEng.Core;
+using Xunit;
+
+namespace MrGameEng.Core.Tests;
+
+public class SceneSystemsTests
+{
+    private struct Velocity : IComponent
+    {
+        public float X;
+    }
+
+    private struct Translation : IComponent
+    {
+        public float X;
+    }
+
+    private sealed class MoveSystem : QuerySystem<Translation, Velocity>
+    {
+        protected override void OnUpdate()
+        {
+            foreach (var (translations, velocities, _) in Query.Chunks)
+            {
+                var t = translations.Span;
+                var v = velocities.Span;
+                for (var i = 0; i < t.Length; i++)
+                {
+                    t[i].X += v[i].X * Tick.deltaTime;
+                }
+            }
+        }
+    }
+
+    private sealed class MovingScene : Scene
+    {
+        public Entity Mover;
+
+        protected override void OnLoad()
+        {
+            Mover = Store.CreateEntity(new Translation { X = 0f }, new Velocity { X = 10f });
+            UpdateSystems.Add(new MoveSystem());
+        }
+    }
+
+    [Fact]
+    public void Update_RunsRegisteredQuerySystem_WithClockDelta()
+    {
+        var context = new EngineContext();
+        var scene = new MovingScene();
+        context.Scenes.Switch(scene);
+
+        context.Clock.Advance(0.5f);
+        context.Scenes.Update(context.Clock);
+
+        Assert.Equal(5f, scene.Mover.GetComponent<Translation>().X, 3);
+    }
+
+    [Fact]
+    public void TimeScale_AffectsSystemDelta()
+    {
+        var context = new EngineContext();
+        var scene = new MovingScene();
+        context.Scenes.Switch(scene);
+        context.Clock.TimeScale = 0f;
+
+        context.Clock.Advance(0.5f);
+        context.Scenes.Update(context.Clock);
+
+        Assert.Equal(0f, scene.Mover.GetComponent<Translation>().X);
+    }
+}