Hello.
For my last game, people said it was too hard and it seems me I'm the only one who finished it. So yes, checkpoints make it less frustrating.
For the jump sound, it's not a programming problem, I just got a last minute unfortunate file compression problem. So you can disable SFX in options when you have heard everything already.
At beggining, I thought it like a metroidvania, so it was a way to restict some areas, but then, I decided to make the game more lineary.
Thanks for playing