I really like the idea of this. It took me a while to work out how to travel without using up all the fuel, but it has a nice feel to it once you work it out. That said, I do think it's too difficult overall, as I only managed to get to open space once out of many tries, and when I got there I was doomed because I didn't have enough momentum to cross it fast enough. The severely limited fuel also meant that I gave up on using any upgrades very early on because I couldn't afford to spend the fuel on them. One thing that might help is if you could store say 10k fuel instead of 1k (but still start with 750), so that you can save up a bunch and then use it on upgrades or crossing open space. I still enjoyed the game though and the visuals and sounds are solid. Nice work!