What the author is missing(my bias, I am currently writing some app design books): 1. It's not puzzles alone, but puzzles in their subject of interest. 2. The

What the author is missing(my bias, I am currently writing some app design books): 1. It's not puzzles alone, but puzzles in their subject of interest. 2. The underlying math is reachable if its presented as a puzzle in their subject of interest. Some puzzles are more sneaky, how many know that the game monopoly is an economic game about cash flows?