Hey good job on the game. I can see this winning best of the month even though I haven't tried the other nominees yet.
I did find some bugs, the most serious of which is the numbering of the diary pages. I'm guessing there was some problem where the page number increments and the pages remaining decrements more than they should, but the page numbers seemed to get too high and the pages remaining went pretty far into the negatives. Also, I wasn't able to proceed past the end of the sand cave even after I found the last diary page and the game acknowledged that I found all of them (even though the pages remaining never said exactly zero). I don't know if the page number bug prevented me from proceeding or if I just couldn't figure out what I was supposed to do. The other bugs I found were mostly just things going through walls.
Apart from bugs, I think the pacing could be improved a bit. I'd like to be able to move faster, destroy enemies and objects in fewer hits, have more checkpoints so death is less punishing, be able to pogo on my first jump, and be able to rocket on subsequent jumps without having to stop jumping first.
Since you seem pretty serious about fixing bugs, I think you'll be interested in checking out my full stream of the game here: https://www.twitch.tv/videos/1835123390
(Note that you should watch the stream soon because it will be auto-deleted in a week)