# Unisu — English

> Unisu is a Sudoku app for iPhone and Android. Play without ads, keep pencil marks and explore the reasoning behind a move when you get stuck.

The website introduces the app and explains Sudoku rules and individual techniques. Guided lessons and further practice are available in the app. The links below open English Markdown versions; each file names its canonical HTML page.

## The app

- [Unisu – Sudoku app for iPhone and Android](https://unisu-sudoku.app/en/index.md): Unisu is a Sudoku app for iPhone and Android. Play without ads, keep pencil marks and explore the reasoning behind a move when you get stuck.
- [Sudoku with no ads: what Unisu offers](https://unisu-sudoku.app/en/sudoku-no-ads/index.md): The current Unisu app contains no ads. Here is what that means for play and the available app features.
- [Play Sudoku offline with Unisu](https://unisu-sudoku.app/en/sudoku-offline/index.md): Puzzles, lessons and saved games are local to the installed app. Downloading the app and sending a request need a connection.
- [Sudoku difficulty levels: what makes a puzzle demanding?](https://unisu-sudoku.app/en/sudoku-difficulty-levels/index.md): The techniques you need tell you more than the number of gaps. See how Unisu organizes its 16 game levels.
- [Sudoku apps compared](https://unisu-sudoku.app/en/sudoku-app-comparison/index.md): Compare Unisu, Sudoku.com, Oakever and Brainium by their documented ads, hint explanations, learning options and supported devices.

## Getting started and learning

- [How to play Sudoku: rules and your first move](https://unisu-sudoku.app/en/sudoku-rules/index.md): One of each number in every row, column and 3×3 box: learn the rules of classic Sudoku and follow a first certain move.
- [Learn Sudoku: a path from rules to techniques – Unisu](https://unisu-sudoku.app/en/learn/index.md): Start with the rules, get comfortable with pencil marks and choose a technique for the situation you’re working on.
- [Sudoku strategy: choosing a technique for the grid](https://unisu-sudoku.app/en/sudoku-techniques/index.md): Singles, pairs, wings and chains address different situations. Find their prerequisites and a guide to the pattern you need.
- [Sudoku help: find a logical next move](https://unisu-sudoku.app/en/sudoku-hints/index.md): Stuck on a Sudoku? Follow a checklist, work through one certain move and see how Unisu’s three hint stages explain the next logical step.
- [Solve Sudoku without guessing: a repeatable search order](https://unisu-sudoku.app/en/sudoku-without-guessing/index.md): Check nearly full areas, then candidates and singles. Build a routine for finding a move you can explain.
- [Sudoku pencil marks: track and update candidates](https://unisu-sudoku.app/en/sudoku-techniques/pencil-marks/index.md): A small note records a possibility. Learn how candidates differ from placements and how to keep them up to date.

## Individual techniques

- [Full House: One gap, one missing digit](https://unisu-sudoku.app/en/sudoku-techniques/full-house/index.md): A Full House has just one empty cell in a row, column or 3×3 box. The one missing digit belongs in that cell.
- [Naked Single: One candidate left in a cell](https://unisu-sudoku.app/en/sudoku-techniques/naked-single/index.md): A Naked Single is a cell with exactly one candidate remaining. Its row, column and box rule out every other digit.
- [Hidden Single: One place left for a digit](https://unisu-sudoku.app/en/sudoku-techniques/hidden-single/index.md): A Hidden Single occurs when a digit has only one possible place in a row, column or box. The cell itself can still have other candidates.
- [Locked Candidates: Use the overlap between a box and a line](https://unisu-sudoku.app/en/sudoku-techniques/locked-candidates/index.md): Locked Candidates: when all candidates for a digit in a box lie on one row or column, remove that digit from the rest of that line outside the box.
- [Naked Pair: Two cells reserve two digits](https://unisu-sudoku.app/en/sudoku-techniques/naked-pair/index.md): A Naked Pair has two cells in one row, column or box with only the same two candidates. Remove those digits from the other cells in that area.
- [Hidden Pair: Two digits have just two places](https://unisu-sudoku.app/en/sudoku-techniques/hidden-pair/index.md): If two digits can appear only in the same two cells of an area, they form a Hidden Pair. Other candidates can be removed from those two cells.
- [Naked Triple: Three cells share three candidates](https://unisu-sudoku.app/en/sudoku-techniques/naked-triple/index.md): A Naked Triple has three cells in one area with just three different candidates between them. Remove those digits from the other cells in that area.
- [Hidden Triple: Three digits confined to three cells](https://unisu-sudoku.app/en/sudoku-techniques/hidden-triple/index.md): A Hidden Triple occurs when three digits have only three possible cells between them in a row, column or box. Extra candidates in those cells can be removed.
- [X-Wing: Two rows, the same two columns](https://unisu-sudoku.app/en/sudoku-techniques/x-wing/index.md): An X-Wing has a digit in exactly two possible cells in each of two rows, in the same two columns. Learn which candidates this pattern rules out.
- [XY-Wing: A pivot and two wings](https://unisu-sudoku.app/en/sudoku-techniques/xy-wing/index.md): An XY-Wing connects a pivot cell X/Y to two cells it sees, X/Z and Y/Z. Whichever digit goes in the pivot, one wing must contain Z.
- [XYZ-Wing: Three candidates in the pivot](https://unisu-sudoku.app/en/sudoku-techniques/xyz-wing/index.md): An XYZ-Wing has a pivot X/Y/Z and two cells it sees, X/Z and Y/Z. At least one of these three cells must contain Z.
- [Swordfish: Follow one digit across three lines](https://unisu-sudoku.app/en/sudoku-techniques/swordfish/index.md): A Swordfish confines a digit’s candidates in three starting rows to exactly three columns. The three required placements use those columns.
- [W-Wing: A matching pair joined by a strong link](https://unisu-sudoku.app/en/sudoku-techniques/w-wing/index.md): A W-Wing links two cells with the same candidate pair through a strong link. Follow the example to see how that connection rules out another candidate.
- [Simple Coloring: Follow one digit in two groups](https://unisu-sudoku.app/en/sudoku-techniques/simple-coloring/index.md): Simple Coloring follows strong links for one digit. When an area has exactly two places for it, one must be true. Alternating groups show those dependencies.
- [Jellyfish: Four lines form one pattern](https://unisu-sudoku.app/en/sudoku-techniques/jellyfish/index.md): A Jellyfish confines a digit’s candidates in four rows to four columns. Learn how this pattern rules out candidates outside those starting rows.
- [Unique Rectangle: Avoid a second solution](https://unisu-sudoku.app/en/sudoku-techniques/unique-rectangle/index.md): Unique Rectangle requires a guaranteed unique solution. This example uses four cells in two boxes to show how that condition rules out a candidate.
- [Finned X-Wing: An X-Wing with an extra possibility](https://unisu-sudoku.app/en/sudoku-techniques/finned-x-wing/index.md): A Finned X-Wing adds a fin to the basic pattern. Remove only candidates that conflict with both the fin and the X-Wing left when the fin is false.
- [XY-Chain: Link cells with two candidates](https://unisu-sudoku.app/en/sudoku-techniques/xy-chain/index.md): An XY-Chain links cells with exactly two candidates each. Follow the example to see where the shared digit at the two ends can be eliminated.
- [AIC: Alternate strong and weak links](https://unisu-sudoku.app/en/sudoku-techniques/aic/index.md): An AIC connects candidates using alternating strong and weak relationships. An assumption can then be followed along the chain to a certain deduction.
- [ALS: Connect almost locked candidate groups](https://unisu-sudoku.app/en/sudoku-techniques/als/index.md): An ALS is a group of n cells in one area with n+1 distinct digits among their candidates. Two such groups can interact through a restricted common candidate.
- [Forcing Chain: Examine two possibilities separately](https://unisu-sudoku.app/en/sudoku-techniques/forcing-chain/index.md): A Forcing Chain checks both candidates of a cell in separate branches. If both branches force the same elimination, you can apply it with certainty.
- [Nishio: Test an assumption through contradiction](https://unisu-sudoku.app/en/sudoku-techniques/nishio/index.md): Nishio tests one candidate by following the moves it forces. If it leaves a cell with no option or a required digit with no place, reject that candidate.

## Help and contact

- [Help with Unisu – Unisu](https://unisu-sudoku.app/en/help/index.md): Answers about hints, lessons, offline play and saved games. For a question about your own app experience, use the contact form.
- [Contact the Unisu team](https://unisu-sudoku.app/en/contact/index.md): A question, a bug or an idea? Tell us what happened. For a bug report, your device, operating system and app version help us investigate.

## Legal information and accessibility

- [Unisu app privacy policy for iOS and Android](https://unisu-sudoku.app/en/privacy/index.md): Privacy policy for the Unisu iOS and Android app: local storage, usage analytics, contact requests, data recipients and your personal data rights.
- [Website privacy](https://unisu-sudoku.app/en/website-privacy/index.md): Unisu website privacy: hosting, contact forms, email notifications, data recipients, retention and deletion, and your rights over personal data.
- [Unisu legal notice and provider details](https://unisu-sudoku.app/en/legal-notice/index.md): Unisu provider details: Stubbe + Finke PartG in Hamburg, contact persons Anna Stubbe and Julian Finke, and the team’s email address.
- [Website accessibility | Unisu Sudoku](https://unisu-sudoku.app/en/accessibility/index.md): Read about keyboard navigation, visible focus and image descriptions on the Unisu website, and find out how to report a barrier.