val s = Staging; s.clear
val (by, ty, lx, rx) = (-200, 200, -300, 300)
def pos(c:net.kogics.kojo.staging.SimpleShape):Point=c.origin+c.offset
var l = for (i <- 1 to 30) yield (s.circle(i * 5, random(20) - 10, 2), i * 0.2, i * 0.3)
tCanvas.onMouseClick{(x,y)=>
    s.circle(x,y,100).fill(red)
}
s.loop {
    l=for ((c, vx, vy) <- l) yield {
        c.translate(vx, vy)
        (c,
        if(pos(c).x>rx||pos(c).x<lx)-vx else vx ,
        if(pos(c).y>ty||pos(c).y<by)-vy else vy
        )
    }
    Thread.sleep(100)
}