Time for action – enemy update and draw

1. Add the Update() method to the Enemy class:

   Public Sub Update(gameTime As GameTime)
     If IsActive() Then
       Dim heading As Vector2 = currentWaypoint - EnemySprite.Location
       If heading <> Vector2.Zero
           heading.Normalize()
       End If
       heading *= speed
       EnemySprite.Velocity = heading
       previousLocation = EnemySprite.Location
       EnemySprite.Update(gameTime)
       EnemySprite.Rotation = 
         CSng(Math.Atan2(
         EnemySprite.Location.Y - previousLocation.Y,
         EnemySprite.Location.X - previousLocation.X))
   
       If WaypointReached() Then
         If waypoints.Count > 0 Then
           currentWaypoint = waypoints.Dequeue()
         End If
       End If
     End If
   End Sub

2. Add the Draw() method to the Enemy class:

   Public Sub Draw(spriteBatch As SpriteBatch)
       If IsActive() Then
           EnemySprite.Draw(spriteBatch)
       End If
   End Sub

What just happened?

Updating an Enemy, begins by checking to see if the enemy is still active. If it is, a heading...