I think 10 boxes would be decent, but it would also depend on playtesting. When it comes to mechanics, I can't think of more off the top of my head, but it would be nice if the mechanics currently in the game were split so there wouldn't be a need for as much of an "explaining" tutorial, but more of giving the player the packaging mechanics first so they can learn that before the demon popups appear. Anyways, this game is very good, thanks for making it :D