Shisen-Sho Mahjong

Shisen-Sho sometimes referred to as 'Shisen', 'Four Rivers' or simply 'Rivers,' is a Japanese tile-based game which uses Mahjong tiles, and is similar to Mahjong solitaire. The objective of the game is to match similar tiles in pairs until every tile has been removed from the playing field. Numerous computer based versions of the game have been developed.

Rules
The aim of the game is to remove all tiles from the board. Only two matching tiles can be removed at a time. Two tiles can be removed if they can be connected by up to three horizontal or vertical lines which pass only through empty spaces. The game is over if future moves are not possible and tiles are left on the board, or the player successfully removes all the tiles.