This game is really good and unique. The music and visuals are solid and overall it's really nicely polished, if a bit short.
One thing I would say, I never actually used A or D because my monkey brain kept brute-forcing the simplest approach (S platform for everything) which worked very well in this case. I do think maybe there should be a limitation, like each stage could have a set amount of each platform type available?
I actually quite liked the speed of the character (only because the responsiveness is good enough to match), though I understand where the other commenters are coming from in saying the speed is too fast. I think it's because the level design is pretty tightly packed with spikes; right now, the spikes are the main lose condition of the game, so it makes sense they would be hard to avoid... but it can be a bit frustrating. I think if you implemented the "limited amount of each platform per level" and then redesigned the levels so that running out of platforms would be the main lose condition, then the player speed would be an asset here instead of a liability. But I have no idea what I'm talking about.
Overall, very cool game and quite polished, I'm impressed you did it in only five days!