Thank you very much for the positive review and the detailed feedback! I agree with pretty much all of the feedback you brought up. For the bug with going out of bounds, that was an issue that I continually had to iron out. I didn't experience any of it for about the last 6 hours of the jam, but I have a few hunches on how it could still happen. Still, I had intended to program in a pause screen with a restart level option, but it just barely didn't get it programmed in in time (there's an art asset for it in the files and most of the logic is there if you manage to lose all your hearts, I was literally just like a half hour short on time).
For the aiming, that was also a tough part to nail down. Ducky has 12 different sprite directions he can face, which means 12 different sets of most animations and a heck of a lot of work for the artists. It feels pretty good I think, but it isn't as fluid as rotating a 3d model would feel. I based it a lot on Star of Providence's aiming, which doesn't technically have a reticle. In hindsight, I think the smaller levels in that game basically give you a reticle there even though it didn't technically have one.
For more visual feedback when an enemy is killed, there's a slightly different audio cue and a death animation for all enemies, but it is hard to see and hear when things are more chaotic. I intended for there to be hit stop as well as some more visual flair on collisions, but again both were skipped due to time. I investigated hit stop a decent amount but my logic on how everything was timed made it too hard to implement before the jam ended.