started on sprite support

UISprite.cs

@@ -0,0 +1,17 @@
+using OpenTK.Mathematics;
+using System.Drawing;
+
+public class UISprite
+{
+    public Vector2 Position;  // Screen pixels (not normalized)
+    public Vector2 Size;      // Size in pixels
+    public Rectangle TextureRegion;  // Which part of atlas to use
+    public Color Tint = Color.White;
+    public float Rotation = 0f;
+    public Vector2 Origin = Vector2.Zero;  // Rotation/scale origin
+
+    public void Draw()
+    {
+        // Draw textured quad using TextureRegion coordinates
+    }
+}