setscreen ("graphics: 500;500")
loop
    for x: 1..500
        Draw.FillOval (x, 200, 100, 100, 180)
        delay(5)
        cls
    end for
    for decreasing x: 500 .. 1
        Draw.FillOval (x, 200, 100, 100, 147)
        delay(5)
        cls
    end for
end loop