This was a really fun game, took me a few hours to beat it, but I felt really accomplished once I did. The exploration was really fun, and the fact that talking to NPC's did help and was actually required to win. There may have been just a bit too much backtracking to get the gems, but I found it OK.
Just a couple of things:
1) When you jump and continue holding up when you land you jump again, I don't know if that is in there on purpose but it got really annoying in the long climbing part.
2) I think there should be one more checkpoint in the climbing area as well. At some point I kept getting really far really easily just to keep dying on one jump, so it was like a minute of easy then I was dead and had to try again.
3) Also, I think it would be nice to get a super secret upgrade to give you one more hit point, even if it was just for the final boss, but that would just be to make it a bit easier on people, not necessary.