I absolutely love most things about this game but there are a few things I had problems with.
The collision between the player characters seemed a bit wonky at times. For example, if my character got switched from blue to red and I then tried to jump over blue I would find myself getting stuck on the other character (this was not limited to those colors, just an example). There was also some stuff with the box collision that didn't feel great. If you grab a box from the edge of a platform and then fall down it will sometimes get caught on the edge of the platform and you'll be forced to drop it there.
Overall, however, the game was great and I had a blast playing it, although I would've liked background music and for the sound effects to be a bit louder.