for (var i = 0 ; i < balls.length ; i++) {

        if (balls[i].x + RADIUS > 0 && balls[i].x - RADIUS < WINDOW_WIDTH) {

            balls[cnt++] = balls[i];

        }

    }

    balls.length = cnt;

    //while( balls.length > cnt ){

    //    balls.pop();

    //}