your code
shuttle(300,100,9000);
mothership(300,400);
wall(100,150,100,350);
wall(75,150,200,150);
wall(250,150,250,350);
wall(350,150,350,350);
wall(225,150,385,150);
wall(225,350,385,350);
wall(450,150,450,350);
wall(425,150,550,150);
alien(300,250,300,225);