Time for action – building the AsteroidManager class

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

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

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

3. Add the following declarations to the AsteroidManager class:

   private int screenWidth = 800;
   private int screenHeight = 600;
   private int screenPadding = 10;
   
   private Rectangle initialFrame;
   private int asteroidFrames;
   private Texture2D texture;
   
   public List<Sprite> Asteroids = new List<Sprite>();
   private int minSpeed = 60;
   private int maxSpeed = 120;
   
   private Random rand = new Random();

4. Add a helper method that will be used in the AsteroidManager constructor:

   public void AddAsteroid()
   {
       Sprite newAsteroid = new Sprite(
           new Vector2(-500, -500), 
           texture, 
           initialFrame, 
           Vector2.Zero);
       for (int x = 1; x < asteroidFrames; x++)
       {
           newAsteroid.AddFrame(new Rectangle...