Controls: F fires thrusters. Left and right as expected - at least when your feet are on the ground. Physics implements gravity, friction and ground contact.
Source and SWF
Edit 2009/09/09: New key! "D" = hover. New physics! You can now L/R in the air. It's not as effective as running, but it does work. And air friction isn't nearly as strong as ground friction.
This is turning out to be quite a fun little tech demo for me. Now I need some cool background artwork and character animation for the JPGuy. Some terrain would be nice, too...
Edit 2009/09/10: New key, "R" resets position to (200, 200). Note that this doesn't change your velocity. Also, size is now 400x800 so you have more space to play.