Mahjong is a traditional Chinesee game. Shanghai version is a single player variant of the game.
The game is played with all Mahjong tiles - 144 separated into following groups:
Dots - 9 tiles 4 pcs each.
Bamboo - 9 tiles 4 pcs each.
Symbols - 9 tiles 4 pcs each.
Winds (cardinal directions) - 4 tiles 4 pcs each.
Dragons - 3 tiles 4 pcs each.
Flowers - 4 tiles.
Seasons - 4 tiles
To remove 2 tiles they must be identical. There is an exception of the rule - 4 season tiles and 4 flower tiles. Sinse they have no matching pair, they can be collected directly with each other. For example, Winter and Summer, Spring and Summer, etc.
A tile is said to be open or exposed if over it there is no tile and at least from one other side (left or right) there is also no tile. You can remove two matching tiles from the board if they are both "opened".
The aim of the game
The goal is to remove all matching tiles as fast as possible. The timer starts when you first click on a tile. Be aware that no every game can be finished, and there can be situation when one game can be solved but removing some tiles in not right order can make the game unsolvable.