游戏的着陆器，不是降落在着陆台上，而是通过

我想让这款xna游戏的着陆器在着陆台上成功着陆，然后播放声音，然而，它正好通过，声音仍然播放。完整的代码是：

namespace MoonLander
{
  /// <summary>
  /// This is the main type for your game
  /// </summary>
  public class BasicLunarLander : Microsoft.Xna.Framework.Game
  {         
    GraphicsDeviceManager graphics;
    SpriteBatch spriteBatch;
    SoundEffectInstance EndGameSoundInstance;
    Texture2D BackgroundImage;
    Texture2D LandingImage;
    SoundEffect EndGameSound;
    int LanderPosX;
    int LanderPosY;
    Texture2D LandingPadImage;

    public BasicLunarLander()
    {
        graphics = new GraphicsDeviceManager(this);
        Content.RootDirectory = "Content";
    }
    /// <summary>
    /// Allows the game to perform any initialization it needs to before starting to run.
    /// This is where it can query for any required services and load any non-graphic
    /// related content.  Calling base.Initialize will enumerate through any components
    /// and initialize them as well.
    /// </summary>
    protected override void Initialize()
    {
        // TODO: Add your initialization logic here
        LanderPosX = 100;
        LanderPosY = 0;
        base.Initialize();
    }
    /// <summary>
    /// LoadContent will be called once per game and is the place to load
    /// all of your content.
    /// </summary>
    protected override void LoadContent()
    {
        // Create a new SpriteBatch, which can be used to draw textures.
        spriteBatch = new SpriteBatch(GraphicsDevice);

        // TODO: use this.Content to load your game content here
        BackgroundImage = Content.Load<Texture2D>("background");
        LandingImage = Content.Load<Texture2D>("lander");
        LandingPadImage = Content.Load<Texture2D>("landingpad");
        EndGameSound = Content.Load<SoundEffect>("crowdcheer");
        EndGameSoundInstance = EndGameSound.CreateInstance();
    }
    /// <summary>
    /// UnloadContent will be called once per game and is the place to unload
    /// all content.
    /// </summary>
    protected override void UnloadContent()
    {
        // TODO: Unload any non ContentManager content here
    }
    /// <summary>
    /// Allows the game to run logic such as updating the world,
    /// checking for collisions, gathering input, and playing audio.
    /// </summary>
    /// <param name="gameTime">Provides a snapshot of timing values.</param>
    protected override void Update(GameTime gameTime)
    {
        // Allows the game to exit
        if (GamePad.GetState(PlayerIndex.One).Buttons.Back == ButtonState.Pressed)
            this.Exit();

        if (Keyboard.GetState().IsKeyDown(Keys.Down))
        {
            LanderPosY = LanderPosY + 2;
        }
        if (Keyboard.GetState().IsKeyDown(Keys.Up))
        {
            LanderPosY = LanderPosY - 2;
        }
        if (Keyboard.GetState().IsKeyDown(Keys.Left))
        {
            LanderPosX = LanderPosX - 2;
        }
        if (Keyboard.GetState().IsKeyDown(Keys.Right))
        {
            LanderPosX = LanderPosX + 2;
        }
        // TODO: Add your update logic here
        Rectangle rectLander = new Rectangle(LanderPosX, LanderPosY, LandingImage.Width, LandingImage.Height);
        Rectangle rectLandingPad = new Rectangle(350, 500, LandingPadImage.Width, LandingPadImage.Height);
        if (rectLander.Intersects(rectLandingPad))
        {
            EndGameSoundInstance.Play();
        }
        base.Update(gameTime);
    }
    /// <summary>
    /// This is called when the game should draw itself.
    /// </summary>
    /// <param name="gameTime">Provides a snapshot of timing values.</param>
    protected override void Draw(GameTime gameTime)
    {

        // TODO: Add your drawing code here
          spriteBatch.Begin();
        spriteBatch.Draw(BackgroundImage, Vector2.Zero, Color.White);
        spriteBatch.Draw(LandingImage, new Vector2(LanderPosX, LanderPosY), Color.White);
        spriteBatch.Draw(LandingPadImage, new Vector2(350,500), Color.White);
        spriteBatch.End();
        base.Draw(gameTime);
    }
  }
}

希望你能帮我解决这个问题，谢谢大家抽出时间。