I think that there must be some issue with the way you're applying force to the player that is causing some framerate-dependent behavior.
I found the game very difficult to progress through and impossible to win (despite maxing stamina and energy, I could only make it to ~3600 distance).
But when I set my monitor's refresh rate as low as it will go (48hz, default is 120), it's very easy to get to the end.
There's also a bug where you can't make a purchase if you have the exact amount the purchase requires. You have to have 1 more than that.
Anyhow, loved the artwork and that the project is open source.
edit: Oh! I see on the submission page that another jammer identified the same two issues already!