I played the game until the end and I like it. XD
The puzzle at the 2nd floor are kinda hard to get. But, when it's solved, I feel really happy with the solution XD
The songs are really beautiful, and it's match with the feeling of the game I think. So it's really great. XD
By the way, I found a way to get the 2nd floor key twice by leaving and entering the room.
At that time, I went to the center room first though, and then going back to the chest room to get the 2nd floor key twice. I don't know if it's intentional or not. But, I'm letting you know in case it's not intentional.