Maybe their program is glitched, but it's pritty easy to make a ou device with it. Take a very thin rectangle, put an axis on the middle, put a spring from very near the axis to the centre of a small ball (as small as they get, or one size up). Make the spring about K 1 - 10 N/m, make air resistance, 0.1 kg/m-s, when let go the spring sould swing below the rotating rectangle, or just hang there. It's starts fast and then slows down to a speed that it stays at, to start it fast just start the ball on the rectangle. And gravity normal.
Someone posted the trial version of WM2 somewhere, (thank you!)