Hey JustGamerMe. I know that you're familiar with pressing Space to jump, but the reason why I chose the Z key to jump is because I was used to playing games on emulators, and having the Z key to jump just always felt natural to me, but I'll add the Spacebar to jump once the jam is over.
Also, the reason why I didn't add a checkpoint system is because this game is designed to be short but challenging, and to sink obsessive hours into, and also falls into the core gameplay loop: Die -> Retry -> Die -> Retry -> repeat ad nauseum. Plus, this game isn't designed to be easy at all. I mean, I'M not the only one who made a tough-as-nails platformer, you're the one that made Mr. Teacup, right?
Anyways, Thanks a lot for enjoying my game though! I'll try to fix some of the suggestions you mentioned.
(Note: Oh, and for my font choice, I have gone with the BoldPixels font, because it has a pixel-art look, and for two things: 1. I wanted a retro feel for the font, since that's what this game is based on, and 2. I needed a pixel art font fast, anyway.)