protected override void UnloadContent()
{
camera = null;
spaceship = null;
skybox = null;
}
protected override void LoadContent()
{
spriteBatch = new SpriteBatch(GraphicsDevice);
device = graphics.GraphicsDevice;
Mouse.SetPosition(device.Viewport.Width / 2, device.Viewport.Height / 2);
originalMouseState = Mouse.GetState();
billboardEffect = this.Content.Load<Effect>("Shaders/billboard_effect");
camera = new Camera(device);
lifeTexture = this.Content.Load<Texture2D>("Sprites/spaceship_sprite");
explosionParticleTexture = this.Content.Load<Texture2D>("Sprites/explosion_particle");
shieldSprite = this.Content.Load<Texture2D>("Sprites/power_up_shield");
shrinkSprite = this.Content.Load<Texture2D>("Sprites/power_up_shrink");
timeFont = Content.Load<SpriteFont>("Fonts/Courier New");
collisionEngine = new CollisionEngine();
particleEngine = new ParticleEngine(explosionParticleTexture, billboardEffect, device);
soundEngine = new SoundEngine(this.Content);
skybox = new Skybox();
skybox.LoadModel(this.Content, effect);
spaceship = new Spaceship();
spaceship.LoadModelAndTexture(this.Content, effect);
torpedoes = new List<Torpedo>();
powerups = new List<Powerup>();
LoadAsteroids();
}