One of the most difficult games i have played in the jam. First boss was easy, second was difficult bcs it's patterns are very unpredictable and hard to avoid but when you use the dash and special attacks effectively you can beat it. Third boss was easy too. I don't know if it's intended as a weakness but i go near it spam kick then dash away from it when he throws the bomb, then go near it and spam kick again, rinse and repeat. I felt like i cheesed the game but what the hell :) 4th boss is like impossible level difficulty. Again it's attacks are totally unpredictable, no telegraphing. Special attack is almost useless against it. Every time i try to do the special attack on it i get hit and it does so little damage. Definitely not worth it. The most useful tactic for me is to get near it spam kick and dash or jump away from it like i did it on the 3rd boss. But it has a shit ton of health and can kill you with like 2-3 hits. I managed to take it's health down to half. If i tried more maybe i could have kill it(i think i almost tried 10 times)but there was a bug which annoyed me so much that i quit playing it at that point. When it corners you to the edge of the screen, there's no way you can escape it and it beats you to death while you scream in frustration. Jump, dash, nothing works at that point and i died like i think 3-4 times.
Other than that, the artstyle of the game is not bad especially considering that it was handcrafted by you in a month but i saw very good 2d art in this game jam. I agree to other comments that the art looks inconsistent. The background images are too muddy. Character design needs some work as well. I like the visual design of the bosses as well as their attack patterns.
To make it short, it's a fun and challenging game. You gotta fix some bugs and may consider adjusting the difficulty a bit. Nice work!