Simple and cool. I both like and dislike how sometimes the same key does 2 actions. On one hand - I did not expect it and it was super convenient in some cases. On the other - it sometimes doesn't allow you to progress and you have to wait it out. Random idea: maybe add a button that instantly switches to the next combination?
Oh, and sometimes the change happens mid-air, which usually leads to level restart and is not fun.
A timer that shows how much time until next change might generally improve the experience.
In any case, good job! :)