I did not expect this game to take so long. I've kinda been playing it on and off for 10 hours, all without closing my browser. The game has such a ridiculous amount of content for a jam, and the map is well designed, although I did find myself getting lost a lot, madly backtracking for around an hour. On my playthrough, I didn't collect enough abilities in the residential area, and ended up somehow ending up in the green area with only one shift jet and no shift extend, leading to me spending half an hour trying to do stupid skips I didn't even know were skips. (This was entirely my fault though.)
The platforming of this game is extremely satisfying. It's kinda rare to see proper jump buffering, coyote time and jump height control in a jam game, but it's executed really well here. Also, despite the character being two shapes, it's really satisfying to bonk your head on the ground using the character's air rotation and hear that noise as you land. The one annoyance is lack of air control, but I understand that adds to the feel of the character. Maybe a little more air control would be nice, but not too much.
Also, the main shift mechanic feels absolutely useless once you get it, although it's pretty cool, as it's only really used for opening certain doors. Thankfully it's upgraded quickly to become much more interesting and diverse, but I feel like from the get-go you could have increased the time before the player slows to a halt, so it can be used to increase jump height a little more than it already does if you time it right. However, this slowing time should be drastically decreased when falling, as it's incredibly demoralizing trying to slow your fall with it only to see the cool trail effect go further down - it's meant to be a hover... (I do appreciate the interesting take on the theme though - shifting shapes around instead of shapeshifting.)
On a random side note, HOW do you do that insane jump right from that screen in the fourth screenshot??!! I know you're meant to have three shift jet unlocks at this point, but I just never seem to make it on the attempts my shift jet doesn't get screwed over by the screen transition (y'know, when the direction of shift jet changes because your mouse is in a different place relative to the player). I never made it up there in the end. Also, why does the shift jet have to be in the opposite of mouse direction? I know it's meant to feel like a sort of launch, but it would just feel so much better if it launched TOWARDS the mouse cursor, like Ori's bash.
Also, the game feels a little empty. I understand you spent most of the time on content, but even small deco like those seashells and parasols at the beach would have gone a long way if you used them a lot more. More frequent enemies would also have help. Also, try making different variations of tiles to add more visual interest. In my game, I sorta spammed them around places of interest to (hopefully) attract the player's attention, and places that looked empty. The bottom part of this tutorial is sort of what I'm talking about.
Apart from what I covered in that little rant, it's a solid game that I quite enjoyed.