INTRODUCTION Tanbo is a board game which is played with a Go set. The initial setup is shown in Figure 1. More than just “new rules for an old game,” Tanbo is a unique, robust alternative to Go. Draws and ties cannot occur in Tanbo. Mark Steere invented Tanbo in 1993.

OBJECT OF THE GAME During play, stones of both colors are added to and removed from the board. Eventually however, all stones of one color will be removed while at least one stone of the other color remains. The player who still has one or more stones on the board after all opposing stones have been removed is the winner.

BASIC MOVES Players take turns adding their own stones to the board, one stone per turn, starting with Black. You must place your stone onto an unoccupied point which is horizontally or vertically adjacent (hereafter “adjacent”) to exactly one of your on-board stones. You cannot put your stone on a point which is not adjacent to any of your stones, nor can you place your stone adjacent to two or more of your stones. It doesn’t matter how many (if any) opposing stones are adjacent to your newly added stone.

Figure 2 shows all of White’s legal moves, depicted by W’s. Points not marked by W’s are not legal moves for White. As long as there are stones of both colors on the board, there will be a move available. Players are not allowed to pass on their turn.

ROOTS Tanbo is a game of “roots,” or groups of connected, like-colored stones. Players start the game with eight single-stone roots each. When placing a stone as described in the preceding section, you are connecting your stone to, and expanding, one of your roots. The basic move rule - your newly added stone must connect to exactly one of your other on-board stones - precludes the formation of clumps and closed loops in roots. And it precludes the merger of roots.

ROOT REMOVAL The “current root” is the root you connect a stone to on your turn. A “bounded root” is a root which has no possibility of expansion. If your move bounds one or more roots, including the current root, you must immediately remove the current root, and only the current root, while it is still your turn. If your move bounds one or more roots, not including the current root, then you must immediately remove all of the roots which were so bounded while it is still your turn. There should not be any bounded roots on the board at the conclusion of your turn.

In Figure 3, White’s move bounds three roots, including the current root. Since the current root is among the bounded roots, only the current root is removed. (Notice that no roots are bounded at the conclusion of White’s turn.) In Figure 4, White’s move bounds two roots, not including the current root. Since the current root is not bounded, all of the roots which were bounded by White’s move are removed.

AUTHOR’S NOTE Feel free to copy, distribute, profit from, or do whatever you like with this document and the game of Tanbo. However, please don’t change the name or the rules, and please attribute the game to me, Mark Steere. Other games I invented: Quadrature, Impasse, Byte, Diffusion, and Cephalopod. For more information see marksteeregames.com.

Copyright (c) December 2005 by Mark Steere