This is a great game for your first jam (and especially starting late!) You even have a boss fight and everything, which is super cool!
Would you like some advice, or would you prefer me just to stick to compliments? Either way, this is a lovely little game - I especially liked the lighting. Drui is also very cute, I love his design!
I think the biggest thing I'd point out is the camera/viewport - when I was playing I noticed that it followed the player so closely I couldn't see enemies below me when I jumped. Maybe zoom it out a little or make sure you can see both enemies and player at once within the camera view. (The movement was nice, though! Otherwise, a very smooth camera.)
I also noticed a lot of jittering/switching sprites, which sometimes interfered with jumps and movement - you can prevent this with state machines, so my advice would be to do some research on those to avoid this popping up next time! It can really hurt any kind of precise movement, which you generally need in platformers.
