Traditionally, go is played with 181 black and 180 white go-ishi (flat, round pieces called stones) on a square wooden board (goban) checkered by 19 vertical lines and 19 horizontal lines to form 361 intersections; more recently, it has been played electronically on computers and on the Internet. Each player in turn (black moves first) places a stone on the point of intersection of any two lines, after which that stone cannot be moved. Players try to conquer territory by completely enclosing vacant points with boundaries made of their own stones. Two or more stones are “connected” if they are adjacent to each other on the same horizontal or vertical line, as are the white stones in group e in the figure-->. A stone or a group of stones belonging to one player can be captured and removed from the board if it can be completely enclosed by his opponent's stones, as white is by black in groups a, f, and g and prospectively in groups b and e in the figure. A stone or group of stones is “live” (not captured) as long as it is connected to a vacant intersection, as are the black stones in groups c and d and the white stones in b and e. A stone cannot be placed on a point completely surrounded by enemy stones unless it makes a capture by so doing, as white does in group c. Groups of stones are in effect invulnerable if they contain an “eye,” which consists of two or more vacant points arranged such that the opposing player cannot place his stone on one of the points without that stone's itself being captured. The black stones in group d possess such an eye. The black stones in group c in the figure, however, do not possess an eye, and a white stone placed on the indicated point would result in the complete enclosure and thus the capture of the black stone group. A player's final score is his number of walled-in points less the number of his stones lost by capture.