Trigon Puzzles

The Trigon impossible triangle

If you like Sudoku, you'll love Trigons

They're made of triangles, they run on pure logic, and they are enormous fun. Each triangle shows you its centre number — the total of its three sides. The sides are blank, and working them out is the whole game.

No maths beyond adding up. No guessing needed, ever. Just that lovely feeling when a number clicks into place and three more suddenly become obvious. Fair warning: people who start one at breakfast have been known to still be at it by lunch.

No payment. No app to install. Just you and the numbers.

A bit of chess, a bit of crossword, a lot of fun

Trigon borrows something from every game worth playing. The deduction of Sudoku. The thinking-ahead of chess. The satisfying click of a crossword answer. The weighing-up of backgammon, and the shape-sense of Go.

  • Logic
  • Mental arithmetic
  • Memory
  • Pattern spotting
  • Thinking ahead
  • Patience

And because it's built on numbers, it doesn't care what language you speak or how old you are. A nine-year-old and a ninety-year-old can sit at the same table and both have a proper go.

You get the totals. You work out the rest.

Triangular dominoes are fitted together into a shape. Each triangle carries a number on all three sides and a centre number that adds them up.

You're handed every centre number and not one of the sides. Where two triangles meet they share a side, so the number is the same for both — crack one triangle and you've handed yourself a clue about its neighbour.

Start with the zero. A centre of 0 can only ever be 0+0+0. From there it's one deduction after another, all the way home.

Dax's rule: "Never put in a number because it will fit. Only put in a number because nothing else will fit."

Watch the how-to video

A little man walks across a real Trigon puzzle with a big pencil. He finds the nought and writes in its three zeros, strikes 000 off the key, then finds the nine and writes in three 3s.

Not one of these came out of a computer

Sudoku is generated by the million, at the press of a button, for nothing. Trigons are not. Every single one was worked out on paper, by hand, by a man called Alan Frazer Dackers — Dax to everyone who knew him, The Boffin to the rest.

He graded the difficulty of each one himself. He and Lester Jordan produced enough for a new book every month for thirty months.

3,252

puzzles, every one by hand

60

books

0

generated by computer

hours of mental exercise

Dax and Lester have both died. No new Trigon will ever be made. What you see here is the complete and final collection.

Read the whole story

Get a pencil. And a rubber.

This is a pencil-and-paper game and it's meant to stay that way. You'll change your mind, rub things out, and change them back. Everybody does — including the people who made them.

Every book comes as a PDF you download and print at home, as many times as you like. Print one page over breakfast, or the whole book for a holiday. Prefer a proper printed book on the shelf? Those are available too.

About sixty puzzles a book, with every answer in the back — so you're never truly stuck, only temporarily beaten.

See the sixty books

A real Trigon puzzle page: a hexagonal grid of triangles outlined in red, yellow and blue, centre numbers filled in, side numbers blank.

Sixty books. Four sizes. One rule.

The 333 series is a coffee break. The 444, 555 and 666 get bigger, longer and considerably more stubborn. Every book mixes them up, easiest first.

Browse all sixty

Start now, for nothing

Three ways in, and two of them cost you absolutely nothing.

Today's puzzle

One puzzle a day, the same one for everybody, from the 333 series. Small enough for a coffee break. A fresh one at midnight.

Play now

A free book

Twelve puzzles across all four sizes, the solving guide, and every answer. Print it, sharpen something, begin.

Download free

The full collection

All sixty books. Every puzzle Dax ever made. The complete and final set, and there will never be another.

See the books

One free book, on its way

Leave your email and the sample book comes straight back. After that we'll only write when there's a new book or something worth solving. Stop it whenever you like.