Logic Pad

It started as one sentence, said to Claude on my way out the door: “start making me an app that generates those logic puzzles … just figure it out.” I would sack a consultant for a brief like that. By the time I was back there was a working generator. It had even guessed the right puzzles — the magazine kind, with a short story, a column of clues and a stair-step grid of ticks and crosses.

One answer, every time

A logic puzzle with two answers is broken, and you only find out after doing all the work. So Logic Pad never stores a puzzle. It picks a random solution and adds true clues until nothing else fits. Then it removes every clue it can live without, and checks that exactly one answer survives. The puzzle number is the seed: the same number always rebuilds the same puzzle, which makes it easy to share and easy to argue over.

Rather more than logic grids

It now does crosswords in three sizes, codewords with a hidden message under the key, and nonograms that can be solved by line logic alone. The sudoku is graded by the hardest technique each puzzle needs, with a guide that explains X-wings in plain language — which I had assumed could not be done. Since 2026-09-22 it also does hashi, word searches and word wheels. The logic puzzles are dealt from 222 short stories, from the 426 bus to a church-hall bake-off. Once a story is published, its wording is locked for good. Somebody may be holding a printed copy.

Paper still wins

Any mix prints as a book, with the answers at the back and a QR code on every puzzle that opens its checker. Safari once turned a 24-page book into 27. So every build now prints a test book in both Chrome and Safari, and refuses to ship if either gets the page breaks wrong.

Case Files

The part I did not ask for. Thirty-four mysteries, each told in chapters, each chapter locked behind a puzzle. Only one is a murder; the rest are thefts, swaps and hoaxes. Solve the grid, read on, name the culprit. The checker proves every case can be reasoned out from its own clues, so the answer is earned rather than guessed.

It is free, and it still works with the phone in flight mode.