Nice sprite work and lighting! Loved your approach to the dynamic room camera.
Some of the rooms felt unnecessarily empty, which was unfortunate because I otherwise enjoyed your learning/challenge progression.
The cost of failure on some platforming sections was worse than death. Having me repeat the same 30 seconds of slow platforming just to get back to the same jump and potentially miss again is a fast way to kill engagement.
I really like the way you introduce the swim mechanic. Having it be near-unavoidable teaches players it's ok - in a genre where water often means death - early before they need to deal with it. Smart design, well done.
Tiny polish change, having your big skele sprite flip to point in the direction of the next door would've been more intuitive.
I like how each area has its own "thing". Moving platforms, water, etc. It keeps the pacing varied and stops me from getting bored.
I wish some sections had quicker alternate routes back (like the upwards snaking water tunnel), again because repetition without mixing it up kills engagement. The only exception to this is your "Sorry" sign which made me laugh as I returned the way I came.
The section with death by falling and enemies should've taught these things as dangerous as everything up until now has been safe to touch. I've been taught that falling is always ok, so sweeping out the rug in this way felt confusing and unfair. I hope this section has checkpoints beyond the room entrance, as having to repeat slowly going down that ladder after death wasn't fun.
Great ending! Nice.
You were clearly very smart about your scope, sticking to simple mechanics, but executing them well enough to get me to play through the whole thing. Well done!