Really great game. I think it's got a lot of potential, it just needs a bit of polishment on the movement.
You should try adding an acceleration to the player instead of making it immediately move at full speed when you press a key. Another thing I think would benefit the game is a larger ground detection hitbox. Many times when playing the platform jumps I would press the jump button a bit after I left the platform and the character wouldn't jump.
I loved when you introduced the dash into the game and the gravity inversion mechanic has a lot of potential.
It's a quite punishing game, but I love it.