Shisen-Sho (四川省 Shisenshō; "Sichuan Province"), sometimes referred to as '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.
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 only if they can be connected with a maximum of three lines. Lines can be only horizontal or vertical, but not diagonal. Lines may cross only the empty border. 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.