public void UpdateAliens()
{
foreach (var alien in Obstacles.OfType <Alien>())
{
AlienBehavior.MoveAlien(alien);
}
}
public Mars(Size bounds)
{
Bounds = bounds;
AlienBehavior = new AlienBehavior();
CenterOfThePlanet = new Point(Bounds.Width / 2, Bounds.Height / 2);
_obstacles = new List <IObstacle>();
}