Fun game. Good PS1 aesthetic and nice sound design.
I wish some of the tricky to get boulders (the ones that require you climb and do some platforming) actually gave something. It was disappointing putting in all that work and coming back empty handed.
I also almost gave up after 10 minutes when I had 9 keys and couldn't figure out where the last one was. Took me another 10 minutes to find and get it (and it required me to climb back up a second time because I fell when trying to catch the key).
I didn't know there was a sprint key. I only found out now after reading comments.
I have no idea how to get ending 1. XD
Would be nice to have a button to return to title after getting an ending. After I got ending 2 it just stayed there and I had to force refresh to give the game another try.
Additionally, a sound cue when finding a key would be useful. I found out I had left behind one key after I circled around from a different part of the map. Apparently too much rock debris hid it from view.
Oh and I clipped through geometry in one of the small hills on a side. It really didn't lead anywhere but I tried climbing anyway and fell through. XD