Some bugs/oversights:
-You can't activate checkpoints with your head or body, this may have been intentional, but i think if you could activate them by throwing your head, it could open up a lot of puzzle possibilities
-If you throw your head into a wall directly in front of you then, without moving, press the throw button again as soon as it touches your body, the head will be thrown in the other direction (I know it's not a big deal, but this tiny bug could become something worse if it goes unnoticed)
-If you throw your head in mid-air while turning around, both the body's throwing animation, and the head while it's being thrown will be backward, but the timings pretty tight on this one (once again, not a big deal, and for all I know, it could have been intentional, I just thought I'd let you know)
-If you throw your head immediately after picking it up, your body won't emit an electric charge, this can be used to cheese the third-last puzzle, if this was intentional, that's really good, it allows the player to take alternative routes, but if it was unintentional, I'm just letting you know
-when you throw your head into a wall directly in front of you , then jump into your head, you won't pick it up, showing that you can't interact with your head until it's reached the full length of the throw, once again, if this was intentional, great, but if it's unintentional, this could hold players back from performing extremely niche tricks
All of these are nitpicks, honestly, you've made something really special here, and I can't wait to see how the final product turns out, i hope that some of the stuff that i mentioned in my monster of a review will help you out, because i can really see this idea going a long way. Good luck :)