Ok, finally be able to play it :) Finished it in 880 sec and 92 deaths O_o
Firstly, well done for your first jam! I can see you put a lot of work here. There's some effort in level design and the nes aspect (graphics and sound). It's a choice you made and it's consistent!
The game is pretty hard though, I had some difficulty with the character that slides, especially as you ask for some really precise jumps. I never felt totally in control which is really important for a platform game. Nevertheless, it's just a question of tweaks in your movement physics, and maybe players would just be used to it as the game goes on (it's too short here to figure it out).
It also lacks some little background story and music but overall it's a pretty nice game, and with some potential above all! Congrats.