public void Move()
{
Point tail = PointList.First();
PointList.Remove(tail);
tail.Clear();
Point head = GetNextPoint();
PointList.Add(head);
head.Draw();
}
internal void Move()
{
Point tail = PointList.First();
PointList.Remove(tail);
Point head = GetNextStep();
PointList.Add(head);
tail.Clear();
head.Draw();
}