Algodoo

The circle changes direction when you change its mass and simulaton frequency.
It gets destroyed by two ways. Gravity and movement.
Note: Do not delete the axle or the magic will be vanished from existence
Also, it sometimes deletes the touching object. Also it deletes anything attached with a axle, spring and fixate (Fixates do not work if it attached to background). Even whole ropes gets deleted when in contact!
The circle of spinning does not delete anchored objects since it is not a killer