新增场景策略适配

source/src/Utils/Screen.ts

@@ -0,0 +1,14 @@
+module es {
+    export class Screen {
+        public static width: number;
+        public static height: number;
+
+        public static get size(): Vector2 {
+            return new Vector2(this.width, this.height);
+        }
+
+        public static get center(): Vector2 {
+            return new Vector2(this.width / 2, this.height / 2);
+        }
+    }
+}