Thanks so much for this feedback. I'm still on the fence as to whether or not I should keep working on this or move to another project, so it's great to hear some encouragement.
An earlier prototype of the game actually gave you upgrade points every time you died, and they'd ramp up depending on how much damage you delivered before death. I thought it made the game too easy, though, so I put a small wall before your first upgrade point. Basically it's been hard to find the right balance, so I totally understand it may need more work.
As for the bug, that's really interesting! I've played this countless times now, and have never seen that one. Were you on Mac or Windows?
In any case, thanks again for this. Gave me lots to think about.