A string of stones is captured by playing into string's last liberty. In the diagram white stones (A) are captured when black plays into B. A stone string consists all the stones connected by lines. A string does not connect diagonally.
An example game continuation is shown. White 1 cannot capture the black stone. Black 2 could connect black stone, but here it does not do it. White 3 may capture black stone, as stones 1 and 2 changed the whole-board position.
One of the players takes black "stones" and the other player takes white "stones". The board is a grid of 9 by 9 lines. The game starts with 4 stones are on the board as shown in the diagram. Black player starts the game. Each player plays a single stone of their own color. A player can play to any empty intersection. A player may not pass. Once the stone is played it is never moved to another intersection.