your code
mothership(500,400)
wall(100,50,100,400)
wall(50,550,250,550)
wall(200,100,200,500)
fuel(100,400,500)
fuel(300,50,200)
fuel(500,150,300)
planet(150,150)
planet(400,50,"mars")
alien(300,300,500,300)
planet(250,350,"jupiter")