Educational5 min · Sep 22, 2026
Hidden Triples: A Deep Dive
Hidden triples are rare and worth the wait. The digit-position scan that finds them, and the two common false positives.
Sudokly Blog
Essays on sudoku, history, mathematics, technique and culture. Published Tuesdays.
- Cultural5 min · Sep 8, 2026
Inside Nikoli
The Tokyo magazine that turned Number Place into sudoku has been hand-crafting puzzles since 1980. The strangest and most durable puzzle business in the world.
- Educational4 min · Sep 1, 2026
Working Memory and Sudoku
Sudoku leans hard on working memory. Whether it improves the resource as well as exercising it is a question with a smaller answer than you might hope.
- Practical4 min · Aug 25, 2026
The Back-to-School Pack
Free printable sudoku for the first month of term. Differentiation built in, kids' supplement included, classroom-ready.
- Practical4 min · Aug 18, 2026
Difficulty Labels Explained
Easy, medium, hard, expert, evil. The labels correspond to required techniques, not clue counts. What each tier actually demands.
- Educational4 min · Aug 11, 2026
X-Sudoku: A Friendly Walkthrough
X-sudoku adds two diagonal constraints to classic. The grid solves faster from the centre out, with the same techniques.
- Educational5 min · Aug 4, 2026
Naked Triples: A Deep Dive
Naked triples extend naked pairs to three cells. The pattern hides in plain sight because the three cells do not need matching candidate sets.
- Cultural4 min · Jul 21, 2026
Howard Garns and Number Place
Sudoku was invented in Indianapolis in 1979 by a retired architect named Howard Garns. He never knew it would reach a billion players. The small history nobody tells.
- Educational4 min · Jul 14, 2026
Flow State and Sudoku
Sudoku ticks every box that flow-state research lists for absorbed attention. What that means, and what it does not mean.
- Practical4 min · Jul 7, 2026
The End-of-School-Year Pack
Free printable sudoku for the last two weeks of term. Mixed difficulties, kids' supplement included, ready for the classroom.
- Practical4 min · Jun 30, 2026
The Daily Sudoku Habit
Daily habits stick when they remove the decision. How to anchor a sudoku habit to something you already do, and what to do on bad days.
- Educational4 min · Jun 23, 2026
Samurai Sudoku: A Friendly Walkthrough
Five overlapping 9x9 grids in a single shape. Samurai is easier than its size suggests, once you know the rhythm.
- Educational5 min · Jun 16, 2026
Hidden Pairs: A Deep Dive
Hidden pairs are the inverse of naked pairs and easier to miss. The scan flip that finds them, with a worked example.
- Cultural4 min · Jun 9, 2026
Wayne Gould: The Man Who Gave Sudoku Away
A retired New Zealand judge spent six years writing a sudoku generator and gave the output to newspapers for free. The story of the man behind the 2004 boom.
- Educational4 min · Jun 8, 2026
Sudoku and Stress: What It Actually Does
Sudoku as stress relief is a small claim with a real basis. The displacement effect, the research, and when the puzzle is the wrong tool.
- Practical3 min · Jun 6, 2026
The Summer Pack 2026
Free printable sudoku for the long summer afternoons. Twenty puzzles, mixed difficulties, solutions on the back, no signup.
- Practical4 min · Jun 4, 2026
Starting a Sudoku Without Guessing
The first ten placements are where most guessing happens. A clean opening routine that finds real moves instead of speculation.
- Educational4 min · Jun 2, 2026
Jigsaw Sudoku: A Friendly Walkthrough
Jigsaw sudoku replaces the 3x3 boxes with irregular regions. Once the visual chaos settles, it plays almost exactly like classic. Here is the plan.
- Educational5 min · Jun 1, 2026
Naked Pairs: A Deep Dive
Naked pairs are the first elimination technique most solvers learn and the one most often misused. The precise pattern, worked example, and the three common mistakes.
- Cultural4 min · May 28, 2026
The Times of London, November 2004
How a single newspaper appearance on 12 November 2004 turned a Japanese magazine puzzle into a global obsession within a year.
- Educational4 min · May 26, 2026
Sudoku and Aging: The Honest Answer
Older readers are the largest sudoku audience. Whether the puzzle helps the aging brain is a real question with a smaller answer than the headlines suggest.
- Practical4 min · May 25, 2026
What to Print Before You Go
Sudoku is a near-perfect travel puzzle: no battery, no signal, no fuss. What to pack for a flight, road trip or weekend away.
- Practical4 min · May 23, 2026
Systematic Scanning: The End of Random Staring
Most stuck moments are scanning problems, not puzzle problems. A clean digit-by-digit method that finds placements where random scanning would not.
- Educational4 min · May 21, 2026
Killer Sudoku: A Friendly Walkthrough
Killer sudoku looks intimidating because of the cage sums. It's actually friendlier than hard classic, once you know the bag of tricks. Here are the essentials.
- Educational4 min · May 19, 2026
A Pencil-Mark Workflow That Actually Works
Half-marked sudoku grids lie to you. The four-step pencil-mark workflow that keeps medium and hard puzzles honest, plus the cardinal sin to avoid.
- Cultural7 min · May 18, 2026
Sudoku and the Brain: What the Science Actually Says
Sudoku is good for you, but probably not in the way you have been told. An honest look at what the research shows, what it doesn't, and why people keep playing anyway.
- Practical9 min · May 17, 2026
Sudoku for Absolute Beginners: Your First Ten Puzzles
A plan for the first ten puzzles you ever play. What to look for, what to ignore, and the small habits that keep you from quitting in frustration.
- Practical11 min · May 16, 2026
How to Solve Sudoku Step-by-Step
A working method for solving sudoku, ordered from the simplest scan to the moves that crack hard puzzles. Use it as a checklist whenever you get stuck.
- Educational7 min · May 15, 2026
Sudoku Rules Explained in Five Minutes
Three rules, one grid, no maths. A quick, complete guide to the rules of sudoku with examples of what counts as valid and what does not.
- Educational8 min · May 14, 2026
What is Sudoku? A Plain-English Guide for Beginners
Sudoku is not a maths puzzle. It is a logic puzzle that uses digits as labels. Here is what it actually is, in plain English, and why it caught on.