almost finished this beast

Source/Demos/Sandbox/Systems/RenderSystem.cs

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+using Microsoft.Xna.Framework;
+using Microsoft.Xna.Framework.Graphics;
+using MonoGame.Extended;
+using MonoGame.Extended.Entities;
+using MonoGame.Extended.Entities.Systems;
+
+namespace Sandbox.Systems
+{
+    public class RenderSystem : EntityDrawSystem
+    {
+        private readonly GraphicsDevice _graphicsDevice;
+        private readonly SpriteBatch _spriteBatch;
+        private ComponentMapper<Transform2> _transformMapper;
+
+        public RenderSystem(GraphicsDevice graphicsDevice)
+            : base(Aspect.All(typeof(Transform2)))
+        {
+            _graphicsDevice = graphicsDevice;
+            _spriteBatch = new SpriteBatch(graphicsDevice);
+        }
+
+        public override void Initialize(IComponentMapperService mapperService)
+        {
+            _transformMapper = mapperService.GetMapper<Transform2>();
+        }
+
+        public override void Draw(GameTime gameTime)
+        {
+            _graphicsDevice.Clear(Color.Black);
+            _spriteBatch.Begin(samplerState: SamplerState.PointClamp);
+
+            foreach (var entity in ActiveEntities)
+            {
+                var transform = _transformMapper.Get(entity);
+
+                _spriteBatch.FillRectangle(transform.Position, new Size2(3, 3), Color.LightBlue);
+            }
+
+            _spriteBatch.End();
+        }
+
+    }
+}