The Christmas Puzzle Advent Calendar
Book 1 of Quipsome Mix, our themed puzzle series. 96 puzzles, 24 days, Large print. Mid-November 2026.
Puzzles with exactly one answer.
Every sudoku, crossword, maze and word ladder in a Quipsome book is built by software and then handed to a solver. The solver works it out the way you would, then checks there is no second answer. If there is one, the puzzle is thrown away.
Don't take our word for it.
This is the day 1 sudoku from our first book. Press the button and our solver will work through it, one step at a time, then count how many ways it can be finished.
Day 1 sudoku, gentle, 25 numbers given
1582721697539763651291364
Solutions found: ?
We checked every way this grid could be finished. There is one. That's our standard.
Bold black numbers are printed in the book. Red numbers are the solver's.
The count runs in your browser, right now. Nothing is pre-recorded.
How a puzzle is proved
- Generate.
- Software builds the puzzle: a grid, a word list, a quotation. It’s quick, and it never gets bored.
- Solve.
- A separate solver works the puzzle the way a person would, using fair techniques only. If it has to guess, the puzzle is out.
- Prove.
- The solver counts every possible answer. One is the only acceptable number.
- Grade.
- The techniques the solver needed set the difficulty. A sudoku that needs an X-wing is tough; one that only needs simple steps is gentle. Nobody squints at it and guesses.
Book one's sudokus, in numbers
- Sudokus
- 24, one a day, and every one has exactly 1 solution.
- Day 1
- Gentle. The solver needs 3 simple techniques.
- Day 24
- Tough. The solver needs 7, including a swordfish: a pattern you spot across three rows at once.
Word searches and cryptograms are a different sort of puzzle: there's no logic to prove, so they aren't part of the count above. Cryptograms use quotations from authors long out of copyright.
Puzzle books
Quipsome Mix: themed books with a mix of puzzles. A bit of everything, and a theme to hang it on.
Found a mistake? If you're sure a puzzle has two answers, or none, email [email protected]. We'd genuinely like to know, and we'll run it through the same solver.