Make your own printable sudoku booklet or play on your phone. Scan puzzles from a newspaper or a sudoku book, add a few generated at the difficulty you like, and SudokuSnap lays them out four to a page with every answer at the back. Print a copy each and race a friend through the same puzzles, or take a week of sudoku somewhere without a screen.

Every puzzle plays on your phone too. The scanner finds the grid in the photo, reads the digits and shows you exactly what it read, so you can correct anything before you start.

MAKE YOUR OWN SUDOKU BOOKLET
• Add puzzles from the camera, your gallery or the generator, and mix all three
• Pick a difficulty for every generated puzzle, so one booklet can run from one star to five
• The booklet is laid out as the pages it prints on, and puzzles drag into any order
• Four puzzles to a page, each one numbered, with every answer on the pages at the back
• Print it, save it as a PDF or send it on, straight from the preview
• Print a copy for each player and race to the last digit
• Take a week of puzzles on a flight, to the beach, or to someone who would rather use a pen
• Any single puzzle prints on a page of its own too, with its answer on the next

SCAN A SUDOKU FROM PAPER
• Point the camera at the page, or pick a photo from your gallery
• The grid is found, straightened and read on the phone
• Every digit is marked confident, unsure or doubtful, so you know where to look
• Tap any cell to see the original photograph up close and fix a misread digit
• The whole scan runs on the device, offline, with no upload and no waiting

PLAY THE WAY YOU DO ON PAPER
• A large grid with cells big enough for a thumb
• Pencil marks, undo, redo, erase and a reset that asks first
• The row, column and box you are working in are highlighted as you go
• A hint explains the next step in words instead of filling the answer in for you
• Choose whether mistakes are marked as clashes, marked outright, or not at all
• Long press a digit to highlight every cell holding it

NINE LEVELS, FROM EASY TO HARD
• Generate a sudoku at any of nine difficulties, or type one in by hand
• One star to five, counted in halves, so the step up is never a cliff
• Every generated puzzle has exactly one solution, and is solvable by reasoning
• A free daily sudoku that is the same puzzle for everyone, every day

KEEP EVERY PUZZLE
• Every sudoku you scan, type in or play is kept, sorted into completed, scanned and uncompleted
• Give any puzzle a name of its own
• Sort a list by when you last played it or by when it arrived
• A streak counting the days you finished something, with a calendar of them
• Totals, time spent and your best and average time at each of the nine ratings
• All of it counted, never estimated, and all of it stays on your phone

LEARN THE TACTICS
• How to play, the rules, and a tactics page that draws out pointing pairs, box line reduction, naked and hidden pairs, X-wings, Y-wings and swordfish on real grids
• The same techniques the hint uses, so the app never asks you to guess

MADE TO LOOK AT
• Six themes, each with a light and a dark version: Classic, Newsprint, Slate, Sepia, Moss and High contrast
• Digits set in Atkinson Hyperlegible, a face drawn by the Braille Institute to keep confusable characters apart

FREE, WITH NO ACCOUNT AND NO ADS
• No sign in, no account, and no server holding your games
• No advertising, and no analytics of the app's own
• Nothing to buy, and no subscription
• Your photographs are read on the phone and never uploaded

SudokuSnap works offline. The puzzles are generated on the phone and the scanner is built into the app, so a train with no signal is as good a place for a sudoku as any.