Adds new Layer class

examples/game/lib/layer.dart

+part of sprites;
+
+class Layer extends Node with SpritePaint {
+  Paint _cachedPaint = new Paint()
+    ..setFilterQuality(FilterQuality.low)
+    ..isAntiAlias = false;
+
+  void _prePaint(PaintingCanvas canvas, Matrix4 matrix) {
+    super._prePaint(canvas, matrix);
+
+    _updatePaint(_cachedPaint);
+    canvas.saveLayer(null, _cachedPaint);
+  }
+
+  void _postPaint(PaintingCanvas canvas, Matrix4 totalMatrix) {
+    canvas.restore();
+    super._postPaint(canvas, totalMatrix);
+  }
+}

examples/game/lib/sprites.dart

@@ -21,6 +21,7 @@ import 'package:vector_math/vector_math.dart';
 part 'action.dart';
 part 'color_secuence.dart';
 part 'image_map.dart';
+part 'layer.dart';
 part 'node.dart';
 part 'node3d.dart';
 part 'node_with_size.dart';