Thank you very much for the comment!
I kind of agree about the movement thing. During the jam I was thinking about giving the player double jump and dash as basic movement or somewhere near the start and then building upon this with current upgrades. But sadly I felt I would be completely defeated by level design if I did that. Also I am so happy you liked the lore snippets, as you say it is just a small thing, but I felt adding them could be nice for some background lore, without too much dialogue.
I understand what you mean about the breakable platforms, it may look slightly janky, but I also tried to build some jumping puzzles around that. It also applies to them on waterfalls as I wanted the player to not really have stable ground there, for added difficulty. But honestly I can see how it could also become problematic. About the laser crystals, it was a last minute change, because before I felt they wouldn't shoot at you at all when you ran past them, so admittedly I probably tuned it too much to the other side. Lastly the boss, those are all fair points. I was quite unsure how to tune the difficulty for him and in the end I did notice on the last day that he is probably a fair bit too easy, but didn't manage to do a lot about it. Also I really appreciate you telling me about the telegraphed attacks. I felt I did a bit of it in the animations(both boss and small crystals go up, and slime below them rises before their attack) but I can see how it is not enough, I will definitely try to improve upon it in the future. And there is nothing wrong with being that guy, I believe I know what you mean with the tilemaps and it may be because of how I separated them for optimization. I was hoping it wouldn't be too noticable, but I will try to hide it better :D
All in all, thank you for playing and giving a feedback, I appreciate it!