The piano/math puzzle is interesting, but that's pretty much about it, rest of the game is just a lot of pixel hunting for hidden keys and gems. The small safe box in the trycicle room has no clues for what the number is...had to resort to walkthrough on that one.
For anyone interested on how the piano/math puzzle works:
In one room, there is a blackboard that points out that A = Square-root of 16, which means A = 4. The book that gives you a key among other hints, give you a sequence like 584-76-597. If you look at the piano keys, they are arranged in a sequence like this D E F G A B C. If you put A as the value 4 and go incrementing one by each letter, B = 5, C = 6, D = 7 and so forth, meaning the sequence 584-76-597 equals to BEA-DC-BFD in piano keys.