public static void collideRegularAndRepelent(RegularBall b1, RepelentBall b2)
{
b2.color = b1.color;
b1.speed.dx *= (-1);
b1.speed.dy *= (-1);
}
public static void collideRegularAndMonster(RegularBall b1, MonsterBall b2)
{
b2.radius += b1.radius;
Engine.balls.Remove(b1);
}