Minesweeper
Numbers Are the Only Evidence
A grid of three sizes with 10, 40 or 99 mines hidden under it. Open a safe square and it tells you how many of its neighbors are mined, and from those counts alone you work out where the rest are. The first square you open is never a mine; open one later and the game ends at once.
When Deduction Runs Out
Most of a board can be settled by pure reasoning: a number and its uncovered neighbors often admit exactly one arrangement. But some positions genuinely do not. Two different mine layouts fit every clue you have, and no amount of thinking separates them - you have to guess, and you can lose a perfectly played game. Telling those two situations apart is the whole skill, and it is harder than it sounds. Deciding whether a given Minesweeper position is even consistent was proved to be NP-complete in 2000, which puts the puzzle in the same computational company as the problems nobody expects to solve quickly.
How to play
- Left click opens a square, right click flags one you believe is mined.
- Press both buttons, or Shift-click, on a number whose flags are all down to open its other neighbors at once.
- Work the edges of what you have opened; the interior rarely tells you anything new.
- When no certain move exists, take the guess with the fewest ways to be wrong.
