Clear the board by matching free tiles in pairs
A tile is free when nothing sits on top of it and either its left or its right side is clear. Match two free tiles with the same face to take them off. Every deal here is built so it can be finished.
Tiles are stacked in layers. A tile can be taken only while it is free: no tile covering any part of it, and no tile directly against it on the left, or none on the right. Tap one free tile, then a second one with the same face, and the pair disappears.
Flower tiles match any other flower, and season tiles match any other season — those are the only pairs that do not have to be identical. If you run out of moves, shuffle the remaining tiles; the board stays solvable.
Mahjong solitaire borrows the tiles of mahjong, a four-player game that took shape in China in the nineteenth century, but not its rules. The solitaire form is far younger: it was written as a computer game in the early 1980s, and the version bundled with Windows from 1990 onward introduced the stacked "turtle" pile to a very large audience. The tiles themselves carry the older tradition — three numbered suits, the four winds, three dragons, and the flowers and seasons that stand apart from the rest.
The whole game rests on one rule about which tiles may be lifted. A tile is available only if nothing rests on top of it and one of its long sides is open, so the pile has to be unwrapped from the outside in. That turns a simple matching exercise into a question of order: two identical tiles may be visible, yet taking them now can bury a pair you will need later.
Not every arrangement of tiles can actually be finished, which is why a randomly shuffled pile is often a dead end through no fault of the player. Boards here are built the other way round, by laying pairs into positions that are free at that moment, so a complete solution always exists — the challenge is finding it rather than hoping the deal was kind.