About

About Tango Unlimited

Tango Unlimited is a free, independent version of the sun-and-moon logic puzzle made popular by LinkedIn's Tango, built and run by one developer. This page says who that is, why the site exists, and exactly how every board is made.

Who makes it

Tango Unlimited is made by Ikuhei Kure, an independent developer based in Japan who builds small daily puzzle games for the web and iOS. The same person makes the Tango Unlimited iPhone app (same puzzles, same dates), the sister sites Poople Unlimited and Krillion Unlimited, and the multi-game site Puzzlune. There is no company and no team.

Why it exists

The original gives you one board a day and nothing to practise on. We wanted unlimited boards in more than one difficulty, every past day kept playable, and above all a hint that teaches: not "this cell is a sun" but "this cell is a sun because no three of the same may touch". Tango Unlimited is that site, and it stays free.

How the puzzles are generated

1. A full solution first. The generator builds a complete 6×6 grid that satisfies all three rules: three suns and three moons per line, never three alike in a row, every = and × respected.
2. Then it carves. Givens and signs are removed one at a time, and after every removal the board is re-solved with a solver that only uses human deductions. A clue stays only if removing it would make the board unsolvable by logic.
3. Uniqueness is proved by brute force. A separate exhaustive search confirms there is exactly one solution. Boards that fail any check are thrown away.
4. The daily is seeded by the date. The seed is the date itself, so everyone in the world gets the same board, the iPhone app gets the identical one, and the archive can rebuild any past day exactly. Each archive page lists how many givens and signs that day had and how many forced steps the solver needed.

What's different from LinkedIn's Tango

• Unlimited boards in easy, medium and hard; the original has one a day.
• A free archive of every daily, with the solution and the reasoning on each day's page.
• Hints that name the rule, an undo button, and an optional mistake marker you can switch off.
• Our own boards. The rules are shared; the puzzles are not copied.

How the site runs

Tango Unlimited is a static website: no accounts, nothing to install, progress and streak in your own browser. It is supported by ads and free to play. Details are in the privacy policy. Tango is a puzzle game published by LinkedIn; Tango Unlimited is independent and not affiliated with, sponsored by, or endorsed by LinkedIn Corporation.

Questions, corrections or press: contact.