Neat game you got here! I like the concept of switching between 2d and 3d, gave me a pleasant surprise.
In terms of platformers, one suggestion that I have is improving the feel for player movement - I'd say this makes or breaks a platformer. If it's not enjoyable to move around in an empty room, then it needs some refining. For example, enabling the player to control jump height could be nice; if player holds the jump button, they jump higher in comparison to if they tap the jump button.
Keep up the good work! Good job on the game