private CircleShootEnemy create_CircleShootEnemy(int x, int y)
        {
            CircleShootEnemy e = new CircleShootEnemy(x, y);

            //this.panel1.Controls.Add(e.img);
            if (enemies.LastIndexOf(null) != -1)
            {
                enemies.Insert(enemies.LastIndexOf(null), e);
            }
            else
            {
                enemies.Add(e);
            }
            return(e);
        }
        private void create_CircleShootEnemy()
        {
            Random           robj = new Random();
            int              x    = robj.Next(20, 450);
            CircleShootEnemy e    = new CircleShootEnemy(x, 0);

            //this.panel1.Controls.Add(e.img);
            if (enemies.LastIndexOf(null) != -1)
            {
                enemies.Insert(enemies.LastIndexOf(null), e);
            }
            else
            {
                enemies.Add(e);
            }
        }