haha the old pencil in the cassette trick, I love that little flashback to the past, I think were at the point now where some gamers aren't gonna understand the struggles of us oldies.
The rewind mechanic to create 'crossable platforms' was a well thought out idea and I liked the visuals of it flailing around, the overall art work could do with some iterations but its a short jam game so I understand the struggles of creating art work as a programmer.
The levels could do with some redesign as well, I really dislike when jumps are made almost 'pixel perfect' due to the fact that if I hit my head on the platform above then I will probably fall down the gap and die like this jump here:
and this:
It felt quite brutal to have jumps like this one where I lose lives testing whether its a run and fall or a jump onto (after I fall walk onto the below, I took the screenshot 1 platform early in case I died twice lol), if I were going to create a choice like that then I'd probably put a life pickup on the next part to compensate the player for that.
Because of these bump your head platform jumps, I struggled to get to level 2 after 15 minutes so I'm not sure what else you had after that but I liked your take on the game jam theme a lot.
Oh and the character felt good to control.