Sadly, couldn't figure out how to actually play (so I'm not rating). I drew a sled but couldn't get any thrust and so I'm stuck on the first hill :(
Edit: Figured out what I was doing wrong from watching Josh's stream. I was clicking on the area of the thrusters not the line that makes up the thruster :/
The idea is really cool and has already given me inspiration for a couple prototypes I might want to mess with :). I wish I was better at understanding the physics, so I could make full use of the levels :P