   aim=90
 5 rng = scan(aim):if rng<0 then shot=-rng
10 temp = kbhit(0): if not(temp) then 5
   xvel = xvel + 100*(temp=76 or temp=76+32) - 100*(temp=74 or temp=74+32) - xvel*(temp=32)
   yvel = yvel + 100*(temp=75 or temp=75+32) - 100*(temp=73 or temp=73+32) - yvel*(temp=32)
   goto 5
