Time for action – creating the StarField class

1. Add a new class called StarField to the Asteroid Belt Assault project.

2. Add the following using directives to the top of the class file:

   using Microsoft.Xna.Framework;
   using Microsoft.Xna.Framework.Graphics;

3. Add the following declarations to the StarField class:

   private List<Sprite> stars = new List<Sprite>();
   private int screenWidth = 800;
   private int screenHeight = 600;
   private Random rand = new Random();
   private Color[] colors = { Color.White, Color.Yellow, 
                              Color.Wheat, Color.WhiteSmoke, 
                              Color.SlateGray };

4. Add a constructor to the StarField class:

   public StarField(
       int screenWidth,
       int screenHeight,
       int starCount,
       Vector2 starVelocity,
       Texture2D texture,
       Rectangle frameRectangle)
   {
       this.screenWidth = screenWidth;
       this.screenHeight = screenHeight;
       for (int x = 0; x < starCount; x++)
       {
           stars.Add(new Sprite(
               new Vector2...