Wow, thanks for taking the time to leave such detailed feedback for me!
For the checkpoint system, I definitely that agree that the final two stages (especially during the second run) can feel too punishing when you die near the end. I wanted to design the levels to be short enough to not need checkpoints, but I think I overshot the difficulty on those final two by quite a bit, haha!
I 100% intended to make the character controllable with either arrow keys or WASD, I just always play with arrow keys so I completely forgot before uploading. Oops!
Yeah, the entire second run was probably a bit too tough in retrospect, I think I should have hidden some more second-run exclusive power-ups (maybe some that require the double jump in level 1, 2, and 3) to lower the cooldown and increase the active time on the misty step-immaterial stone power up, and maybe some powerups to reduce knockback as well. Just a few little additions that can help the player get through the tougher sections!
Hmm, I put a bullet timeout so that after a certain distance they disappear, but it's totally possible that I introduced a bug somewhere so they don't actually disappear like they're supposed to, lol! I should look into that, see what I missed. I considered just having the bullets die when they hit a wall, but I thought it would be more fun for the player if they just timed out instead - but I think that might have been a bad assumption on my part.
Thanks again for the detailed feedback, I can't even express how much I appreciate it - it means a lot! And thanks for the kind words as well, I'm really happy to see people enjoying my game! :)