If I were paid a penny for every Game Jam platformer where you shift dimensions... xD
Tbh, the idea is not that fresh. This game is not the worst implementation of this concept though. Even so, I really missed some visuals. The jump animation is just a walking loop which doesn't sound like a big problem in theory, but consider the floaty jumping combined with the fact that you spend more than 50% of the game in the air...
Finally, would be great to make the environment more detailed, as standard Unity cubes certainly serve as decent platforms, but look too simple for the setting.
Still, if itch.io is not lying and that's your first 3d game, it's a solid start.