Add Color record struct, small refactor, create a DaggerFramework.SceneGraph namespace.

TestGame/Circle2d.cs

@@ -1,12 +1,11 @@
 using DaggerFramework.Rendering;
-using System.Drawing;
-
+using DaggerFramework.SceneGraph;
 
 namespace DaggerFramework;
 
 public class Circle2d : Drawable2d
 {
-    public override void OnDraw(in Renderer renderer)
+    public override void OnDraw(Renderer renderer)
     {
         renderer.DrawCircle(32f, Color.AliceBlue);
     }

TestGame/TestGame.cs

@@ -27,7 +27,9 @@ public class TestGame : Game
         while (_renderer.ShouldRun)
         {
             _renderer.BeginFrame();
-            _renderer.ClearBackground(System.Drawing.Color.Black);
+            _renderer.ClearBackground(Color.Black);
+            _renderer.SetTransform(new Vector2(640, 480));
+            _renderer.DrawCircle(16f, Color.Chocolate);
             _renderer.EndFrame();
         }
     }

TestGame/UiLayer.cs

@@ -0,0 +1,22 @@
+using System.Numerics;
+
+using DaggerFramework;
+using DaggerFramework.Rendering;
+using DaggerFramework.SceneGraph;
+
+public class UiLayer : Layer
+{
+    protected override void OnUpdate(double dt)
+    {
+        base.OnUpdate(dt);
+        _time += dt;
+    }
+    protected override void OnDraw(Renderer renderer)
+    {
+        renderer.SetTransform(Vector2.Zero);
+        renderer.DrawRectangle(new Vector2(720 / 2, 1280), Color.Green);
+        renderer.DrawDebugText(new Vector2(720 / 4 - 24, 64), "UI :)", 24, Color.White);
+    }
+
+    private double _time;
+}