Time for action – the enemy manager

1. Add a new module called EnemyManager to the Robot Rampage project.

2. Add declarations to the EnemyManager module:

   #Region "Declarations"
   Public Enemies As List(Of Enemy) = new List(Of Enemy)()
   Private _texture As Texture2D
   Private _initialFrame As Rectangle
   Public MaxActiveEnemies As Integer = 30
   #End Region

3. Add the Initialize() method to the EnemyManager module:

   #Region "Initialization"
   Public Sub Initialize(
       texture As Texture2D,
       initialFrame As Rectangle)
   
       _texture = texture
       _initialFrame = initialFrame
   End Sub
   #End Region

4. Add the AddEnemy() method to the EnemyManager module:

   #region "Enemy Management"
   Public Sub AddEnemy(squareLocation As Vector2)
       Dim startX As Integer = CInt(Int(squareLocation.X))
       Dim startY As Integer = CInt(Int(squareLocation.Y))
   
       Dim squareRect As Rectangle =  
           TileMap.SquareWorldRectangle(startX, startY)
   
       Dim newEnemy As Enemy = New Enemy(
           New Vector2(squareRect.X, squareRect.Y),
         ...