xna-飛碟遊戲

namespace BeginnersGuide_2DGame_Windows
{
    /// <summary>
    /// This is the main type for your game
    /// </summary>
    public class Game1 : Microsoft.Xna.Framework.Game
    {
        GraphicsDeviceManager graphics;
        Texture2D backgroundTexture;
        Rectangle viewportRect;
        SpriteBatch spriteBatch;
        GameObject cannon;
        const int maxCannonBalls = 5;
        GameObject[] cannonBalls;
        GamePadState previousGamePadState = GamePad.GetState(PlayerIndex.One);
        KeyboardState previousKeyboardState = Keyboard.GetState();
        const int maxEnemies = 20;
        const float maxEnemyHeight = 1.0f;
        const float minEnemyHeight = 0.1f;
        const float maxEnemyVelocity = 20.0f;
        const float minEnemyVelocity = 1.0f;
        Random random = new Random();
        GameObject[] enemies;
        int score;
        SpriteFont font;
        Vector2 scoreDrawPoint = new Vector2(0.1f, 0.1f);
        public Game1()
        {
            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()
        {
            base.Initialize();
        }
        /// <summary>
        /// Load your graphics content
        /// </summary>
        protected override void LoadContent()
        {
            spriteBatch = new SpriteBatch(graphics.GraphicsDevice);
            backgroundTexture =
                   Content.Load<Texture2D>("Sprites\\background");
            cannon = new GameObject(Content.Load<Texture2D>("Sprites\\cannon"));
            cannon.position = new Vector2(350, graphics.GraphicsDevice.Viewport.Height -50);
            cannonBalls = new GameObject[maxCannonBalls];
            for (int i = 0; i < maxCannonBalls; i++)
            {
                cannonBalls[i] = new GameObject(Content.Load<Texture2D>(
                    "Sprites\\cannonball"));
            }
            enemies = new GameObject[maxEnemies];
            for (int i = 0; i < maxEnemies; i++)
            {
                enemies[i] = new GameObject(
                    Content.Load<Texture2D>("Sprites\\enemy"));
            }
            font = Content.Load<SpriteFont>("Fonts\\GameFont");
            //drawable area of the game screen.
            viewportRect = new Rectangle(0, 0,
                graphics.GraphicsDevice.Viewport.Width,
                graphics.GraphicsDevice.Viewport.Height);
            base.LoadContent();
        }
        public void UpdateCannonBalls()
        {
            foreach (GameObject ball in cannonBalls)
            {
                if (ball.alive)
                {
                    ball.position += ball.velocity;
                    if (!viewportRect.Contains(new Point(
                        (int)ball.position.X,
                        (int)ball.position.Y)))
                    {
                        ball.alive = false;
                        continue;
                    }
                    Rectangle cannonBallRect = new Rectangle(
                        (int)ball.position.X,
                        (int)ball.position.Y,
                        ball.sprite.Width,
                        ball.sprite.Height);
                    foreach (GameObject enemy in enemies)
                    {
                        Rectangle enemyRect = new Rectangle(
                            (int)enemy.position.X,
                            (int)enemy.position.Y,
                            enemy.sprite.Width,
                            enemy.sprite.Height);
                        if (cannonBallRect.Intersects(enemyRect))
                        {
                            ball.alive = false;
                            enemy.alive = false;
                            score += 1;
                            break;
                        }
                    }
                }
            }
        }
        /// <summary>
        /// Unload any content not managed by the Content Manager
        /// </summary>
        protected override void UnloadContent()
        {
            base.UnloadContent();
        }
        /// <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();
            GamePadState gamePadState = GamePad.GetState(PlayerIndex.One);
            cannon.rotation += gamePadState.ThumbSticks.Left.X * 0.1f;
            if (gamePadState.Buttons.A == ButtonState.Pressed &&
                previousGamePadState.Buttons.A == ButtonState.Released)
            {
                FireCannonBall();