Really cool idea to have physical buttons that can be used as platforms. I do think that kinda limits what the game can do. You can only jump or move horizontally. Using jump input as a block really limits your capabilities.
Lovely art and SFX. Your game is so much more polished than mine that it makes me jealous.
Suggestions:
1. Right click on buttons to bring them back.
2. Slow down time while placing blocks for finicky areas,
3. Have duplicate buttons in the world. Ex: two jump buttons in the world. Place one. Jump over it and so on.
4. Maybe have the jump button act as a trampoline when the player is on it. The right and left buttons could automatically move player as well. This is actually how I planned my game to be. Then it took a different turn.
Good job. It's always eye opening to see someone else do a different take with the same idea.