I like the idea, but the game is a tad unfair at times. Enemies can shoot you from off-screen, do quite some damage and shots are almost impossible to evade. Shooting back will just cost you health as well. I got stuck on platforms and enemies above/below me a few times, causing my early demise. I never made past the key, but maybe I was doing something wrong.
In regards to your comment about them jam in the description: You're right, allowing 96x96 resolutions would make things easier, but having to manage 64x64 is pretty much the point of the jam, isn't it? :D If you're looking for something like you described, try GBJam sometime in autumn, also on itch. You are limited to 160x144 px, 4 colors and the GameBoy controls (DPad, A, B, Start, Select) which you freely assign to any key. Works perfectly for platformers as this one and is quite fun as well.