Pretty cool game! Just a couple things that I thought could be improved:
the music doesn't really exist, the death sounds could be slightly "clearer", the UI text and stuff seems a bit small (at least for my resolution 1920x1080) and i couldn't really make out what some text in the corner said, the camera is a bit too "floaty" for my liking, and finally pressing "continue" in the menu just loads up the level (but makes double jump not work or something i have no idea). Also because of some of those problems, I didn't know how to get past level 3.
Still, the player movement is really nice to control, the film grain effect thingy is really nice, the visuals and stuff are simplistic but aren't bad. The different level difficulties like swapping A and D are pretty cool also, just that (mentioned above), I kept dying in level 3. Or most likely i just suck ._.
Again, nice game!