Well, I don't know how many people work in this one, but I'll assume that was just a single guy.
The idea of multiple characters with unique skills for a puzzle platformer is very nice and I already experimented with this before.
I finished the 3 first levels and played a bit of the other ones and I had some issues with the game:
Controls:
Oh boy, the controls are something, they're not terrible, but they aren't very good. I feel like you could use the mouse to change the characters instead of TAB, also, Press F will switch the cube's scale direction even if I'm not controlling it, also also, I think the use the Up and Down Arrow instead of W and S Keys wasn't a good idea, feels clunky every time I needed to use the Cube.
Visuals and UI:
I'm not against wacky art styles, but this one feels very over the place, lacks consistency between characters, background, VFX, and so on.
The UI in the levels could be better, there's no clear indication of who I am currently controlling at the moment but the sprites got darker, except the blue kid for some reason, which screw everything XD
Level Design & Mechanics:
The puzzles are simple but good, and when I finally stopped to fight against the controls I could solve them very intuitively, but on the other hand I felt complexity spikes between levels, I understand there are just 6 of them, but this in addition with the controls made my experience less enjoyable, also I get stuck in the level that introduces the blue ball, which cannot reach the button(note: while writing this, it came to my mind the probably the kid isn't the only one who can trigger the exit, but then the level per se isn't very intuitive).
Since this game was made within 96 hours, I understand the tutorials being text boxes, but for some reason, neither of them tells the player about the wall jump, which you kinda need to progress in the 2nd level.
I don't know how to feel about the psych meter, it's important for a puzzle to have limitations, but this one doesn't feel well-designed, it's just a limitation that forces you to reset when you run out of energy.
Other Issues:
Speaking of reset, if the kid dies in the middle of the level he just respawns in his origin position, but the other characters don't, so...what's the point? If this happens I would be forced to reset anyway.
This is a minor issue, but if you press W the kid unleashes his Ultra Ego Aura in the same way as the Up/Down Arrows, but nothing happens.
Outro:
Sorry for the insane long essay, but I think there's a very good and promising game here, just needs a lot of polishing, and rethinking some aspects like the controls and visuals, if this is your first game, don't give up, the beginning is always rough and manage schedules and game dev it's always.