Really impressive work, although the game is very hard. I would never have guessed that an unassuming generic switch in a room could affect things in other rooms, so when the only way to return to the hub is to go back in time (therefore undoing the switch press, meaning there are no visible changes in the hub), that just left me lost.
Another thing is that after placing two of the apples and figuring out that they must represent a melody, the game didn't acknowledge when I tried every combination of 3 notes (that had those apple notes) in front of the box with the key.
Even with the ingame hints I had to look at the solutions on the store page and even then I got tired before reaching the end... I guess these things are to be expected when devs make an ambitious and professional quality puzzle game in two days :P