A tricky plataformer, a bit too tricky for me though. The gravity level felt way too tight, and the spikes hitbox seems bigger than their sprite (I guess it's because the entire tile is a hitbox).
I only played until the second gravity level, and my biggest issue is that, so far at least, you are not really controlling two characters. Since the levels are symmetric, you are just controlling the same character with two different views. Maybe later levels introduce a certain level of "desync" between, but I couldn't pass the second gravity.
Either way, the art and sounds are pretty good, while the game itself is a solid, albeit tight, plataformer.
In my opnion, it's a pretty good job for your first game. Keep it up!
PS: Probably the engine's fault, but I had to reload the page after loading the game in other for the controllers to work.