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Mastercode
Board · plays in your browser, no download
A hidden row of colours. Ten tries, and every answer narrows it down.
Where it comes from
Mastermind, the pegboard from 1970 that an Israeli postmaster invented and sold to a British company. It is a short game with a long mathematics: the known answer is that five guesses are always enough, and finding that out took a famous computer scientist and a computer.
How to play
- A row of hidden colours. Find it before you run out of rows.
- Pick a colour at the bottom and it goes into the row. Press ▶ when the row is full.
- The dots do not say which colour — only how many.
- ⌫ clears the last colour.
What makes this one different
A filled dot means a colour is right and in the right place; a ring means it is there but somewhere else. They never say which colour, only how many — so every row you play has to be chosen for what its answer will rule out, not for what it might be.
Ten rows, and the dots on the right are the only thing you ever learn — so the game is not guessing colours, it is designing a question whose answer narrows things down however it comes back. The number at the top is how many rows you have left.