You really ought to mention somewhere that when you change perspective, your 3-D position is the furthest 'forward' point you could be from the current perspective. Took me a while to figure that out.
It would be interesting to combine 2 side-by-side notes to make one note that plays for twice as long. Also, having a page where you could tell it to (for example) play page 1 twice, then page 2 and 3, then back to 2 etc.
Oh that's a great idea!