Free-tile rules, reading the stacks, and choosing the right pair when a face appears four times
Mahjong solitaire borrows the tiles of the four-player Chinese game Mahjong but none of its rules. The tiles are piled into a layered layout, and a single player removes them in matching pairs until the table is empty. The computer version traces back to Brodie Lockard's Mah-Jongg, written for the PLATO system in 1981, and Activision's Shanghai brought it to home computers in 1986 - which is why the game is still sometimes called Shanghai.
Everything is visible from the first move: there are no hidden cards and no dice. What turns it into a puzzle is the stacking. Tiles lower down stay locked until the tiles above and beside them are cleared, so every game is a question of digging the right tiles out in the right order.
On PlayVersusAI, free tiles are drawn bright with white symbols, blocked tiles are dimmed, and your current selection turns purple. Blocked tiles ignore clicks, and clicking a free tile that doesn't match your selection simply moves the selection to it - there is no penalty for a wrong pick.
Rather than the traditional 144-tile turtle, PlayVersusAI deals a compact stepped pyramid. On the Small and Medium layouts the base layer is eight tiles wide and four rows deep, with layers of six by three, four by three and (on Medium) two by three stacked on top. The Large layout widens the base to ten by five and stacks eight by four, six by four and four by four above it. Every upper layer is shifted half a tile downward, so each upper tile straddles two tiles beneath it. The faces are the Characters, Circles and Bamboo suits from 1 to 9, the four winds, the three dragons and a set of flower pictures, and a tile only matches an identical face.
Faces are not simply shuffled onto the board. The game builds each deal backwards: starting from the full pyramid, it repeatedly picks two tiles that would be free at that point, gives them the same face and lifts them off, until the table is empty. Playing those pairs in reverse clears the board, so a solution always exists. Because removing tiles can only ever free other tiles, never block them, any free pair you take on Small or Medium keeps the board clearable - on those layouts every face appears on exactly two tiles, so there is never a wrong choice of partner.
Large has 61 pairs but only 42 distinct faces, so 19 faces appear on four tiles, as they do in a traditional set. That brings back the classic dilemma. When three copies of a face are free you have to pick two, and the one you leave behind may be the only key to a buried tile later. When all four copies are free, take both pairs straight away; there is nothing to gain by waiting. When three are free, match the two that are covering or flanking the most other tiles and leave the one that blocks nothing. Above all, avoid leaving two copies of the same face where one sits directly on top of the other.
If you do reach a position with tiles left but no free matching pair, the game reshuffles the faces of the remaining tiles - using the same backwards method, so the new arrangement is clearable - and tells you it has done so. The completion summary counts reshuffles, so a clean clear with none is the mark of a well-played Large board.
Because the leaderboard ranks time, play for speed and visibility. Start on the tall centre stack: it is the deepest part of the pyramid, and the tiles underneath it stay hidden longest. Prefer matches that uncover something - a top tile that frees two half-covered tiles below beats an edge tile that frees nothing. Work the long base rows from both ends, keeping an eye on the tile second from each end, since it becomes available next. When you see a free tile whose twin is still buried, note what is covering the twin and go after those tiles first.
Most lost seconds come from searching, not deciding. Pick one free tile and sweep the whole board for its twin before moving on, rather than darting between candidates. The suits are easy to tell apart by shape - Characters carry a written numeral, Circles show rings, Bamboo shows sticks - so check the suit first and the number second. Dimmed tiles are blocked, so you only ever need to scan the bright ones.
The layout buttons choose the size and depth of the pyramid. Every deal is generated so that it can be cleared.
| Layout | Layers | Tiles | What to expect |
|---|---|---|---|
| Small | 3 (8×4, 6×3, 4×3) | 62 tiles, 31 pairs | A shallow pyramid where no tile is buried more than two layers deep. The best layout for learning to read free tiles. |
| Medium | 4 (adds a 2×3 top) | 68 tiles, 34 pairs | A tall spine down the middle that leaves the centre of the base buried under three layers. |
| Large | 4 (10×5, 8×4, 6×4, 4×4) | 122 tiles, 61 pairs | Nearly twice the tiles, with 19 faces appearing four times, so the order you match in starts to matter. |
The Matches counter rises by one for each pair removed. Your score is the time from your first click to the last match, and the leaderboard ranks the fastest clears. Personal bests are kept separately for each layout in your browser, while the online table currently combines all three. There is no hint or undo.
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