I got to the sun. How far in is that?
Fantastic physics engine. I've tried developing space/gravity simulators in the past, and they're certainly not easy to get right. You got that.
Definitely very difficult controls...at first. Got really far at one point once I learnt the best timing to fire the thrusters. Once you work out the engines, the rest of the physics kick in and everything makes sense.
That said, I still found achieving an orbit to be nearly impossible. I think you have a fun game without the resource management. Think of an endless runner with your controls. Your score will be how far you manage to fly your ship. A game about achieving maximum speed/distance for minimal force and energy. That's the magic of slingshooting right?