Hello everyone, thanks for the feedback!
Just uploaded a version with a level editor and some other small new features.
The players will now try to stay balanced by moving their arms and legs instead of an upward force applied to their head.
It doesn't have any sounds yet. For the next version I plan to implement sounds, rolling physics for the boulders, a few more items and hopefully replace the art with something better.
you can download it here : https://dl.dropboxusercontent.com/u/95585100/schermutseling.zip