Blog
Notes from the publisher's desk
Solving advice, book news and the case for working on paper.
Paper and pencil
Free printable Sudoku puzzles for solvers who want a real challenge
A Sudoku to print every day, at five levels from Easy to Extreme, with tips on printing, pen or pencil, and where to find hundreds more at the same level.
6 November 2026Read articlePuzzle types
Hashiwokakero rules: how to build bridges without crossing
The rules of Hashiwokakero (Hashi, Bridges) in plain English, with a small worked example and why big grids get hard.
30 October 2026Read articlePuzzle types
The difference between Calcudoku and KenKen, explained
Calcudoku and KenKen look identical. What actually differs is the name, a few cage rules and the grid sizes, and which to try first.
23 October 2026Read articleOur story
Play Sudoku online free: a tour of our Sudoku puzzle player
How the free Hardcore Puzzler Sudoku player works: entering digits, pencil marks, checking your grid, and where the puzzles come from.
16 October 2026Read article