Really cool concept! I liked having to figure out ways to manipulate the character's momentum along with the platform to get through various obstacles.
I'd definitely make the platform thicker for blocking horizontal beams though, getting it in the right position was rather finicky on the second level, and not in a way that was gameplay difficult since the character was stopped while I was working on it. It would also be interesting if you kept more momentum along the horizontal axis so you didn't have to remember to start holding the button again when you switch back if you're not trying a complicated maneuver.
I would love to see more levels with more interesting usages of the mechanic! :)