PhysicsHandler работает не так, как ожидалось - AndEngine

Парни - полный новичок в AndEngine. Я хотел использовать обработчик физики и прошел через примеры andengine. Так что в моем случае у меня есть "шариковый" спрайт, который я могу перемещать прикосновением, и второй "квадратный" анимированный спрайт, который я ожидаю отскочить от стен. Но он просто выходит из экрана. Выручи меня...

    package com.Escapo;

    import org.anddev.andengine.engine.Engine;
    import org.anddev.andengine.engine.camera.Camera;
    import org.anddev.andengine.engine.handler.physics.PhysicsHandler;
    import org.anddev.andengine.engine.options.EngineOptions;
    import org.anddev.andengine.engine.options.EngineOptions.ScreenOrientation;
    import org.anddev.andengine.engine.options.resolutionpolicy.RatioResolutionPolicy;
    import org.anddev.andengine.entity.scene.Scene;
    import org.anddev.andengine.entity.scene.Scene.IOnSceneTouchListener;
    import org.anddev.andengine.entity.scene.background.ColorBackground;
    import org.anddev.andengine.entity.sprite.AnimatedSprite;
    import org.anddev.andengine.entity.sprite.Sprite;
    import org.anddev.andengine.entity.util.FPSLogger;
    import org.anddev.andengine.input.touch.TouchEvent;
    import org.anddev.andengine.opengl.texture.TextureOptions;
    import org.anddev.andengine.opengl.texture.atlas.bitmap.BitmapTextureAtlas;
    import    org.anddev.andengine.opengl.texture.atlas.bitmap.BitmapTextureAtlasTextureRegionFactory;
    import org.anddev.andengine.opengl.texture.region.TextureRegion;
    import org.anddev.andengine.opengl.texture.region.TiledTextureRegion;
    import org.anddev.andengine.ui.activity.BaseGameActivity;

    import android.view.Display;



    public class EscapoActivity extends BaseGameActivity {

private Camera mCamera;
private Scene mMainScene;

//main ball variables
private BitmapTextureAtlas mBitmapTextureAtlas;
private TextureRegion mPlayerTextureRegion;
private Sprite player;
//square
private BitmapTextureAtlas mBitmapTextureAtlas2;
private static final float DEMO_VELOCITY = 100.0f;
private TiledTextureRegion mFaceTextureRegion;
private static int cameraWidth;
private static int cameraHeight;
private Sprite square;
@Override
public void onLoadComplete() {


}

@Override
public Engine onLoadEngine() {

    final Display display = getWindowManager().getDefaultDisplay();

        cameraWidth = display.getWidth();

        cameraHeight = display.getHeight();



        mCamera = new Camera(0, 0, cameraWidth, cameraHeight);



        return new Engine(new EngineOptions(true, ScreenOrientation.LANDSCAPE,

            new RatioResolutionPolicy(cameraWidth, cameraHeight), mCamera));

}

@Override
public void onLoadResources() {



            mBitmapTextureAtlas = new BitmapTextureAtlas(512, 512,

                TextureOptions.BILINEAR_PREMULTIPLYALPHA);

            //square
            mBitmapTextureAtlas2 = new BitmapTextureAtlas(512, 512,

                    TextureOptions.BILINEAR_PREMULTIPLYALPHA);


            BitmapTextureAtlasTextureRegionFactory.setAssetBasePath("gfx/");



            mPlayerTextureRegion = BitmapTextureAtlasTextureRegionFactory

                .createFromAsset(this.mBitmapTextureAtlas, this, "ball.png",

                0, 0);

            //square
            this.mFaceTextureRegion = BitmapTextureAtlasTextureRegionFactory.createTiledFromAsset(this.mBitmapTextureAtlas2, this, "square.png", 0, 0, 1, 1);

            mEngine.getTextureManager().loadTextures(mBitmapTextureAtlas,mBitmapTextureAtlas2);




}

@Override
public Scene onLoadScene() {

     mEngine.registerUpdateHandler(new FPSLogger());



         mMainScene = new Scene();

         mMainScene

             .setBackground(new ColorBackground(0.09804f, 0.6274f, 0.8784f));


         final int PlayerX =(int) ((mCamera.getWidth() - mPlayerTextureRegion

                 .getWidth()) / 2);
         final int PlayerY = (int) ((mCamera.getHeight() - mPlayerTextureRegion

             .getHeight()) / 2);



         player = new Sprite(PlayerX, PlayerY, mPlayerTextureRegion) {

                 public boolean onAreaTouched(TouchEvent pSceneTouchEvent,float pTouchAreaLocalX, float pTouchAreaLocalY) {

                    this.setPosition(pSceneTouchEvent.getX()- this.getWidth() / 2, pSceneTouchEvent.getY()- this.getHeight() / 2);




                     return true;

                 }

             };
             mMainScene.registerTouchArea(player);

                mMainScene.setTouchAreaBindingEnabled(true);

         mMainScene.attachChild(player);
         //square
         final Ball ball = new Ball(2, 2, this.mFaceTextureRegion);
         final PhysicsHandler physicsHandler = new PhysicsHandler(ball);
         ball.registerUpdateHandler(physicsHandler);
         physicsHandler.setVelocity(DEMO_VELOCITY, DEMO_VELOCITY);

         mMainScene.getLastChild().attachChild(ball);

         return mMainScene;

}


private static class Ball extends AnimatedSprite {
    private final PhysicsHandler mPhysicsHandler;

    public Ball(final float pX, final float pY, final TiledTextureRegion pTextureRegion) {
            super(pX, pY, pTextureRegion);
            this.mPhysicsHandler = new PhysicsHandler(this);
            this.registerUpdateHandler(this.mPhysicsHandler);
    }

    @Override
    protected void onManagedUpdate(final float pSecondsElapsed) {
            if(this.mX < 0) {
                    this.mPhysicsHandler.setVelocityX(DEMO_VELOCITY);
            } else if(this.mX + this.getWidth() > cameraWidth) {
                    this.mPhysicsHandler.setVelocityX(-DEMO_VELOCITY);
            }

            if(this.mY < 0) {
                    this.mPhysicsHandler.setVelocityY(DEMO_VELOCITY);
            } else if(this.mY + this.getHeight() > cameraHeight) {
                    this.mPhysicsHandler.setVelocityY(-DEMO_VELOCITY);
            }

            super.onManagedUpdate(pSecondsElapsed);
    }
 }




 } 

Я просто попытался интегрировать пример движущегося шарика http://code.google.com/p/andengineexamples/source/browse/src/org/anddev/andengine/examples/MovingBallExample.java. Где я ошибаюсь?