Rules for this implementation

How to Play Mahjong Turtle

Remove every tile by selecting legal matching pairs. Each generated initial board is built with at least one valid removal path, but your move order can close access and create a dead end.

Objective

Select two free tiles that match to remove them. Continue until the board is empty. The classic Turtle has 144 tiles; the other playable layouts use smaller even counts.

Starting guarantee, not a promise about every later state. Board generation assigns pairs along a simulated legal removal path. A different sequence of player choices can consume a needed match or leave remaining faces behind blocked positions.

The exact free-tile rule

A tile must not be covered from above, and at least one horizontal side must be open.

Both conditions are checked against the positions still present on the board. A tile can have one blocked side and still be free. It is blocked by side neighbors only when both its left and right sides are occupied on the same layer.

Free tile. Tile A has nothing above it. Its left side is open, so the neighbor on its right does not prevent selection.

Blocked on both sides. Tile A is uncovered, but same-layer neighbors touch its left and right sides.

Covered tile. A higher-layer tile overlaps tile A, so A is blocked even though its sides appear open.

Newly opened tile. Removing a legal pair can uncover a lower tile or open one of its sides. Learn Mode highlights tiles whose availability changed.

Matching rules

Select one free tile, then a second free tile with a compatible face. Characters, bamboo, circles, winds, and dragons match only another tile with the identical face. The two category exceptions come directly from the game's match keys:

Flowers: plum, orchid, bamboo, and chrysanthemum match any other flower.
Seasons: spring, summer, autumn, and winter match any other season.

Flowers do not match seasons. A legal pair therefore requires two currently free tiles and either the same ordinary face or membership in the same special group. See every supported face in the visual Tile Guide.

Controls and what they guarantee

New Game: Creates a new seed and a newly generated initial board on the regular game. Daily uses Restart Today or Restart This Challenge instead, keeping that challenge's fixed seed.
Replay Same Board: Rebuilds the initial board from the current seed. It resets the timer, selections, move history, and counters.
Undo: Restores the most recent successfully removed pair recorded in the current play history. It works one supported move at a time and is disabled when that history is empty.
Hint: Highlights one currently available legal pair. A hint identifies a move, not a complete solution or the best strategic choice.
Shuffle: Reassigns the remaining faces among the remaining positions. Shuffle changes the remaining arrangement but does not guarantee that every later state can be solved.
Learn Mode: On / Off: Explains why a selected tile is blocked and reports newly opened tiles after a removal. Learn Mode explains availability and move impact without revealing a full solution.
Fit Board: Scales the complete layout to the available width.
Readable Zoom: On narrow screens, keeps tiles larger in a scrollable board area. It changes only the view, not tile availability.

Keyboard players can Tab into the board, use the arrow keys to move between present tiles, and press Enter or Space to activate the focused tile. The counters report Time, Tiles left, Moves, Pairs open, Hints, and Undos; they do not choose a move for you.

Completion and no-moves states

Removing the final pair completes the game and opens a result dialog. If tiles remain but no legal matching pair is available, the game reports that no moves remain. You can return to inspect the board, use Undo when a recorded move is available, Shuffle the remaining faces, or replay the same initial board.

Undo can move you back toward an earlier decision. Shuffle may make a move available, but it leaves the original generated solution path. This is why an initially valid path does not guarantee success after arbitrary decisions.

Common questions about this game

Does the initial board have a valid solution path?

Yes. Initial generation assigns pairs while simulating legal removals. That proves a route existed at the start; it does not prove that every legal move order will finish.

What does Replay Same Board reproduce?

It runs the current layout and seed through generation again, restoring the starting face assignment while resetting the timer, selection, history, and counters.

How is the Daily Challenge selected?

The visitor's local calendar date is converted to the deterministic seed for the Turtle layout. The same supported date restores the same initial Daily board.

Where is Daily progress stored?

Challenge history, best results, hint and undo counts, and streaks stay in this browser's local storage. They do not automatically follow you to another device.

Is an account required?

No. Regular games, layouts, the Daily Challenge, local history, and learning pages work without creating an account.

How do I diagnose a tile that looks available?

Check cover first, then both horizontal sides. The blocked-tile diagnostics guide walks through each state with coordinate-checked examples.