Very innovative puzzle game, though I have seen a game where your character traverses the surface of a cube once or twice before. I do wish there could have been a bit more to the story than silent acting and a few notes in the author's description here on NG. That and the music not being separate from the sound are my only complaints- I would love to be able to mute just the music so I can listen to my own, but still have all the other sound effects from the game.
The learning curve gets appropriately steeper as the game progresses. I like this. It was stupid tough getting the last few levels finished, but I still managed to figure it out. I now have all 18 diamonds and the super-secret surprise that rewarded my efforts. Now I'm looking for the nine keys, but I've no clue where to go. The game gives no hints about their whereabouts. I can only presume they are hidden within the previous levels since... well, I don't want to spoil too much for the players.
However, dear author, if you are still checking up on this, any hints about the keys would be appreciated.