I have submitted my entry to the Mozilla Game On competition under the ‘hackable games’ category. It can be played online now at: http://austinmarton.github.com/phys-ed/
I developed a basic platformer written from scratch in Javascript using HTML5 canvas and some jQuery. It has a ‘mod mode’ in which the user can view some of what is going on behind the scenes and change some of the physical parameters. Of course I ran out of time in the end but the competition was a great push to at least get a playable prototype out there.
It is released under GPLv3 so please check out or even fork the source code on github!
Austin's blog 