Overall it's a fun game and a nice idea for the theme.
If I had to give feedback for improvements, I think a lot of things have already been said in the comments but I think they are really important too:
- for first time players, add a clear separation from the blocks you can pick and the level
- retry shouldn't remove your blocks, if it happens when you failed the platforming section or if there is ONE block that you need to change it adds some frustration
- make all the blocks necessary for the puzzle, it felt like I didn't do the puzzle as intended as I had a pieces that were not really used and it add clutter to the game space
- Add maybe an option to right click a block to remove it
Even though the list is a bit long, I really enjoyed your game and just want it to be even better 😜