Thanks for the feedback. I can understand some people having concerns about the controls. As I stated, originally, this was an experiment with physics so the controls work based on placing a force on a mass to gain acceleration (and a negative force to decelerate). There is no friction or air resistance modeled so bodies, including the player, will continue indefinitely. In computer games, though, this seems counter intuitive so (even though I personally quite enjoyed the challenge of learning the controls - it reminded me a bit of games like KSP) I'll add an 'arcade mode' with controls which behave more like most people expect.