Notes on puzzles
How to solve a word ladder in fewer steps
Practical ways to get from the top word to the bottom one without wasting rungs, from working backwards to watching the vowels.
The Zebra puzzle and how to solve a logic grid
Five houses, five owners and a question about a zebra. How the classic logic grid works, and a method for solving any of them.
How Tetris got out of the Soviet Union
Tetris was written on a Soviet computer in 1984 and reached the world through a tangle of licences. Here is the short version.
Letter-swap puzzles and the maths of the fewest swaps
When every letter is already on the board, the puzzle is the order. How to count the fewest swaps a scrambled grid needs.
The Monty Hall problem, and why it fools nearly everyone
Three doors, one car, and a host who knows where it is. Why switching wins two times in three, explained without the maths getting in the way.
What makes a good Wordle starting word
There is no single best first guess, but there are good reasons some words beat others. Here is how to think about your opener.
Historical dates that sound wrong but are right
Cleopatra, the pyramids, Oxford and the Aztecs: a few pairs of events whose order surprises nearly everybody.
The first crossword, and how it took over the newspaper
The crossword was first printed in 1913 as a diamond-shaped word-cross. Here is how it became a daily fixture.
Why water sort puzzles are so satisfying
Pouring coloured liquid between bottles sounds too simple to be a puzzle. Here is what makes the genre work, and why it is harder than it looks.
How sudoku got from a New York magazine to the whole world
Sudoku was invented in America, named in Japan and made famous by a British newspaper. Here is how it happened.
Lewis Carroll’s word ladders, and why they still work
The author of Alice in Wonderland invented the word ladder in 1877. Here is how his Doublets worked and why the idea has lasted.
How Wordle went from a gift to a global habit
Wordle began as a word game made for one person to play. Here is how it spread, why the grid of squares mattered, and what changed after it was sold.