修复Vector2.zero引起的引用混乱问题

demo/src/Scenes/Ninja Adventure/NinjaAdventureScene.ts

@@ -2,14 +2,12 @@ module samples {
     import CircleCollider = es.CircleCollider;
     import Flags = es.Flags;
     import SpriteRenderer = es.SpriteRenderer;
+    import ProjectileHitDetector = es.ProjectileHitDetector;
+    import FollowCamera = es.FollowCamera;
 
     export class NinjaAdventureScene extends SampleScene {
-        constructor() {
-            super(true, true);
-        }
-
-        public initialize(): void {
-            super.initialize();
+        public async onStart() {
+            super.onStart();
 
             let playerEntity = this.createEntity("player");
             playerEntity.position = new es.Vector2(256, 224);
@@ -21,12 +19,22 @@ module samples {
             // 移动到第1层 保证自己的图层不会如果增加攻击方式则不会攻击到自身
             Flags.setFlagExclusive(collider.physicsLayer, 1);
 
+            this.camera.entity.addComponent(new FollowCamera(playerEntity));
+
             this.content.loadRes("moon_png").then(moonTexture => {
                 let moonEntity = this.createEntity("moon");
                 moonEntity.position = new es.Vector2(412, 460);
                 moonEntity.addComponent(new SpriteRenderer(moonTexture));
+                moonEntity.addComponent(new ProjectileHitDetector());
                 moonEntity.addComponent(new CircleCollider());
             });
         }
+
+        public update(){
+            super.update();
+
+            this.findEntity("player").position.x -= es.Time.deltaTime * 10;
+            this.findEntity("player").position.y -= es.Time.deltaTime * 10;
+        }
     }
 }