Mahjong Solitaire

Mahjong solitaire is played with the 144 tiles of a mahjong set, stacked in a pattern of five layers. This one is the classic turtle. The goal is to clear the board by taking the tiles off in matching pairs.

You can only take a tile that is free:

• Nothing lies on top of it, not even partly.
• Its left side or its right side is open (no tile right next to it on the same layer). Tiles above or below don't count as neighbours.
• Two tiles match when they are the same: two 5 of Dots, two East Winds, two Red Dragons.
• Flowers are the exception: any flower matches any other flower. The same goes for the four seasons.
• The game is won when every tile is gone. It is lost when no two free tiles match and you can't undo.

There are three suits numbered 1 to 9, four tiles of each: Dots (circles), Bamboo (sticks) and Characters (the Chinese numeral over the sign for ten thousand). Each tile has its number in the top corner here, so you don't need to read the characters.

The honours have four of each too: the four Winds (East, South, West, North, marked E, S, W, N) and three Dragons (Red, Green and White; the White Dragon is the blue frame).

Then there are one of each of four Flowers (plum, orchid, chrysanthemum, bamboo) and four Seasons (spring, summer, autumn, winter). Flowers pair with any flower and seasons with any season.

Click or tap a free tile to pick it, then its match to take both. Picking a tile that is not free shows why it is stuck: covered, or blocked on both sides. Turn on "Highlight free tiles" below the board to dim every tile you can't take yet.

Undo takes back as many pairs as you like. Hint shows a pair from a winning line our solver found from your position, or tells you when the board can no longer be cleared.

When no two free tiles match, Shuffle mixes the tiles left into a new order that can still be cleared. Your game is saved in this browser, so you can close the page and come back.

Most lost games are lost early, by taking an easy pair that a later tile needed.

• Free the long rows first. The end tiles of the middle rows and the tall centre stack hold the most tiles back.
• When three tiles of a kind are free, think before you pair two of them: keep the one that blocks nothing, take the ones that sit on other tiles.
• When all four tiles of a kind are free, take both pairs. That can never hurt.
• Look under the stack: before taking a pair, check whether one of the same kind is buried under the tile you are about to leave behind.
• Flowers and seasons match each other freely, so save them for when you need to open a stuck side.

This puzzle shares its tiles with mahjong, the four-player game from China, but the play is its own. It began as a computer game: Brodie Lockard made it on the PLATO system in 1981, and home-computer versions spread it in the mid-1980s. The turtle stack has been the standard layout since then.