Puzzle Ninja fits neatly into a hole in the problem-solving teachers’ library, with 25 surprisingly diverse one-person games described, all based on a rectangular grid with numerical clues.
Where Bellos’s book is brilliant is that one gets to relive the joy of discovering how the game works, what is possible, and what strategies are effective and efficient, 25 times!
Some of the puzzles have links to graph theory, some to factorisation, but the explicit mathematical skills are not the attraction – instead it’s the chance to talk about ‘what to do when you don’t know what to do’. They puzzles’ rules are all expressed with sublime concision, like a haiku, or like an exam question.
Here’s an example:
The rule: divide the grid below along the dotted lines so that the white squares are completely saturated with L-shapes looking like this (in any orientation):
The grid:
As one Japanese puzzle-writer states: you don’t need to teach students maths, “you only need to give them very interesting puzzles”.