Diagnumb puzzles for teens and adults. These puzzles use subtraction between single digit numbers and deductive reasoning (The process of elimination) between multiple-choice answers to solve, and are timed-based (optional) to rank your score to win. Puzzle solutions are correct when the difference between all numbers next to each other in all diagonal rows =2 or more without repeating a number in any diagonal row. Each book contains a practice puzzle and 30 increasingly challenging new puzzles with solutions. Game rules, definition of game terms, and how to solve are explained using illustrated examples.