def interval():
    on_platform = False
    for plat in platforms:
        if player.get_x() > plat.get_x() - 25 and player.get_x() < plat.get_x() + 25:
            on_platform = True
    if on_platform is False and player.get_y() > -190:
        player.set_gravity_on()
stage.event_interval(interval, 0.1)