Great job on this one! The 2 puzzles I liked the most were the tombstone one and the cauldron one, because they made me think. I absolutely love riddles and because of that I may be biased haha, but I was eager to get a piece of paper (or rather a notepad) and figure it out.
The narrative part of this game is very well written, and the ending cutscene is great.
(spoilers) Poor Nina.
About the other 3 puzzles, the one with the rocks is good and very nice as a first puzzle, the one with the lamps could have less lamps (IMO), and the maze is the only one I didn't like. Mostly because instead of teleporting me to the beginning, when I lost I got back to the main menu, which was anticlimactic. As I knew all the answers I played it again (and saved this time, before going into the maze) and got through it. The movement of the bats is not very intuitive and sometimes they get stuck, it seems.
Other than that, it was an awesome experience, and the mood of the game is fantastic.