Checkers and draughts, done properly

Most checkers apps ship one set of rules and call the rest variants. These five are implemented separately, down to which square is playable and what a king is allowed to do, because a Turkish player and an English player are not playing the same game with a house rule between them.

• English checkers — 8×8, three rows each. Men move and capture forwards only, and a king steps one square at a time.
• International draughts — 10×10, four rows each. Men capture in every direction, kings slide the length of a diagonal, and you must take the line that captures the most pieces.
• Brazilian draughts — the international rules on the small board: flying kings, maximum capture compulsory, faster and sharper.
• Spanish checkers — long-range kings but forward-only men, and a tie-break that decides between two equal captures by counting the kings taken.
• Turkish draughts — 8×8 on every square, sixteen men a side, no diagonals at all. Pieces move straight ahead and sideways, and captured men come off the board immediately.

Online games are paired by rule set and rating, so you meet someone who plays roughly as well as you do. Each rule set carries its own rating: being strong at English checkers says nothing about your Turkish, and the leaderboards agree.

Offline, the computer plays at a range of strengths — from an opponent that lets a beginner finish a game to one that punishes a loose move ten plies later. It runs on the device, so it works on a plane, on a train, and in the parts of the world where mobile data is something you ration.

Two people with one phone can share it: pass-and-play on a single board, no second account and no second device.

Timed online games run on a clock the server keeps, not one your phone keeps. That is a boring engineering detail with one visible consequence: nobody wins because their opponent's connection stuttered, and nobody gains a second by changing a device's system time.

If your connection drops mid-game, the game is still there when you come back.

Any finished game exports as PDN, the plain-text notation the draughts world already uses, and the app reads back files it did not write. Your openings are not locked inside somebody else's database — including ours.

English (US and UK), Polish, German, Spanish, French, Italian, Portuguese, Turkish, Ukrainian and Vietnamese. Rule names differ by country for real historical reasons, and the interface uses the name each country actually uses.