I really like the concept, I jumped out of this jam because of not being able to come up with anything fitting to the theme but this is head on... I don't know if that joke works.
I have sadly not been able to enjoy it too much because of the character movement. My main issue is the head just doing... things. But I don't know how you could've made it much better given that it gotta have that cube rolling thing. One thing you could've done is give some weighty midair control in the style of mario to the head, one that keeps your momentum if you do nothing but changes it when you move (can be a bit hard to implement different jumps when you start out, but learning which kinds of jumps you can make can be important).
I haven't gotten through the entire game (Level 12 was the last I played) so I don't know if you used it but I was interested in seeing the Robot and Heads different movements being used in level design. I feel the Head having a fixed jump height but with midair control while the robot has a controlled jump height could open up for some interesting levels.
I also gotta comment on the level design, I think their biggest issue is the difficulty curve though I'd say that's a bit out of scope for a beginner jam (and it is 1 am and I didn't finish the game so it is impossible for me to judge that). But a few levels also gave me a LevelDesignersFirstLevel-Feel, especially Level 11. Like I get the idea, but what is goin on with that upper layer of platforms, there's absolutely no need for that weird hole inside of them it just gets in the way of the main mechanic of the level: Bringing robot to left side so that he falls onto the switch after you fly through the level.
And about the look of the game I gotta say, the individual assets each look fine on their own but thrown together it is just extremely unfitting. It combines 3 styles of pixel each at a different resolution with mesh-cubes and dynamic lighting. But I still gotta put credit to the fact you managed to make the lighting effects and robot legs work (I haven't been able to do so yet), even if it doesn't look good right now it'll help you make things look good in the future.
And finally the sound design is just real good. Not perfect but it is some solid work.
Hope I haven't been too strict and written something that demotivates you. In the end it is a finished game and you should be proud of that.