Good job, really interesting concept!
For the moment, I passed level 1 and 2, but will come back later to beat the rest.
I am bad at 3D platforms, but I think that even if I wasn't, the game could enjoy some easier challenge regarding that: it put your core mechanic, the spinning gear, in the shade.
To make it a little bit more forgiving, a few suggestions:
- add a Coyote time to your jump
- make the rotating platforms move step by step, with a little pause between each
- make platform mechanics appear gradually, and not all since level 1
Camera-wise, would love a zoomed out one when spinning gears, to make more sense of what you have to do (or just what you do. Had a hard time to understand the wall was opening in level 2).
And maybe make platforms between you and the camera transparent instead of moving the camera, would make it way smoother
On another note, your game could work well as an asymmetric 2 players coop game too, where one sees the entire level, and has to help the other by giving them instruction (like "try spinning this gear... OH IT CLEARS THE PATH where you were locked before!!"), and maybe interact in some ways with the machine (stop this rotating gear for a bit, deactivate this trap...)
Oh, and was pleasently surprised by the changing music between levels
You have a solid concept that deserves to be made a full game, if you want to continue working on it, congrats!