Really interesting player upgrade system! Choosing what stats to prioritize for the different bosses makes an interesting challenge. Although it did turn into a bit of guess-and-check to see whether some new combo would better fit the situation. Also, I would highly recommend adding more visual feedback to show the player when they were getting hit, and when they are hitting enemies. It took me a long time to figure out whether my weapon was doing any damage at all. Also, as others have mentioned, the sounds are bit repetitive and grating, so they should definitely be toned down some. But overall, great job on completing a full game!