The concept and mechanics are really good. Even though it's lacking animations and other elements like audio, I still had fun playing it. However, the game is a little too hard in some parts (or I'm really bad a platformers xD) which might make some players give up early and give some frustration (maybe it's intentional?).
Also, maybe give the players ability to change between both characters whenever they want throughout the levels? It's just a suggestion and I don't know how much it would impact the game's design like levels but I would personaly think it would be a good addition to the game.
Overall, great work and congrats! Hope you had a great time developing the game!