# Brain Focus Books

> Calcudoku and math logic puzzle books in large print, a publishing imprint of Buy One Media.

## The books
- Calcudoku (also called Mathdoku) puzzle books: 500+ machine-verified puzzles per book, each with exactly one solution.
- Large clue type (17 pt), spacious 15.7 mm grid cells and full-size answer keys.
- Series include 4x4 Easy, 5x5 and 6x6, Medium, Hard Logic, Senior Comfort Large Print, and Interactive Mystery & STEM.
- Sold on Amazon in paperback and Kindle: search "Brain Focus" on Amazon.

## How Calcudoku works
Fill the grid so every row and column contains each number once (1 to 4 in a 4x4). Each outlined cage must make its target number with its operation: + (sum), x (product), - (difference of two cells) or ÷ (larger divided by smaller). Numbers may repeat inside a cage only if they are in different rows and columns.

## Links
- Website: https://brainfocusbooks.com/
- Amazon: https://www.amazon.com/s?k=Brain+Focus+Books
- Interactive mysteries from the same publisher: https://theonlyconclusion.com

## About
- Publisher: Buy One Media LLC (https://buyonemedia.com)
- Founder and author: Sean Sandoval (https://seansandoval.com)
- All Buy One Media sites: https://by1.net