The good side:
The art, environment and story are cute.
You can walk faster by clicking twice on your destination.
The music related puzzles were somewhat original.
Death sequences are great (and with almost no consequences).
The last puzzle was ok.The bad side:
It's short with almost no replay value (and mostly just for achievements).
Many screens (about 40%, I counted) serve no purpose besides esthetic/ambience (or hidden fireflies, that unlock artworks). And those that do contain something never have more than one purpose.
There's a bit too much backtracking (which is made worse by the previous point).
One "item" is quite pointless and the related puzzle relies on an unexplained mechanic that you will use only once in the full game. (The cat, although a cute companion, will stay available all the time even though it's used only once, it was forcefully crammed in the puzzle you use it for and combining the pets is used only there.
Another puzzle uses unexplained and specific mechanics. (When you have to combine objects to get rid of the crocodile.
When trying to figure out the notes you hear, the background sounds will make them hard to discern (turning off sfx/music might help, I haven't tried). The notes will also be played in a loop with a quite short pause in between, which leaves only short intervals for you to try and reproduce them.
The girl will sometimes stand in a place that will make it difficult to click on what you actually want. It's also difficult to click on your companions (it will open the inventory most of the time).
Parts of the HUD should be displayed all the time without having to wait or click blindly, at least the button to access the music sheet. Also, switching from windowed to fullscreen is only available in the main menu.
Some notes are too similar and hard to tell apart. (H and I, M and N, in particular.
Most of the puzzles were not fun or satisfying to solve.
All in all, this game is quite disapointing. I was expecting much more from it.
It lacks a lot of polish to make it at least enjoyable, even if short.
The dev team congratulates itself in the credits about finishing the project in 4 months. I have to say that, sadly, it shows...