Time for action – spawning enemies

1. Add the SpawnEnemy() method to the EnemyManager class:

   Public Sub SpawnEnemy(path As Integer)
       Dim thisEnemy As Enemy = new Enemy(
           _texture,
           pathWaypoints(path)(0),
           _initialFrame,
           _frameCount)
       For x As Integer =  0 to pathWaypoints(path).Count - 1
           thisEnemy.AddWaypoint(pathWaypoints(path)(x))
       Next
       Enemies.Add(thisEnemy)
   End Sub

2. Add the SpawnWave() method to the EnemyManager class:

   Public Sub SpawnWave(waveType As Integer)
       waveSpawns(waveType) +=
           rand.Next(MinShipsPerWave, MaxShipsPerWave + 1)
   End Sub

3. Add the updateWaveSpawns() method to the EnemyManager class:

   Private Sub updateWaveSpawns(gameTime As GameTime)
       shipSpawnTimer += CSng(gameTime.ElapsedGameTime.TotalSeconds)
       If shipSpawnTimer > shipSpawnWaitTime Then
           For x As Integer = waveSpawns.Count - 1 To 0 Step -1
               if waveSpawns(x) > 0 Then
                   waveSpawns(x) -= 1
                   SpawnEnemy(x)
      ...