Tanbo

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This article is about a board game. For a martial arts weapons, see: Tambo (weapon)

Tanbo is a board game invented by Mark Steere in 1993. It typically uses a 19x19 Go board, but (like Go) it can be played on larger or smaller boards, depending on the intended length and depth of the game. The game has, however, a very big first move advantage (71% according to Super Duper Games) which makes it almost unplayable in serious competition.

Some Tanbo-related terminology is as follows:

A root is a collection of orthogonally connected stones of the same colour.
A liberty is a location on the board into which a root could legitimately be extended; this is a close analogue to the same term in Go.

The rules of Tanbo are as follows:

Set up a starting configuration of stones. A sample starting configuration on a 9x9 board is as follows:

9
8
7
6
5
4
3
2
1
	a	b	c	d	e	f	g	h	i

The starting configuration should be symmetric, and there should be an odd number of spaces between "adjacent" stones to keep players from using a symmetric strategy. Like Go, Tanbo is played on the lines of the board instead of the squares themselves.

Each player selects a colour of stone to use throughout the game. Black goes first.
The current player must place one stone in such a way that it extends one of his roots; it must be orthogonally adjacent to one and only one stone of its own colour. Consider the following board section, Black to move, with 1s representing legitimate moves and 9s representing invalid moves:

(The empty intersections represent invalid moves as well, but are not shown as such for clarity.) The 9s in the top and middle rows represent moves which are invalid because they would be adjacent to more than one black stone; the 9 in the middle row is invalid because it is adjacent to none. All of the 1 signs are adjacent to one and only one black stone.

The expanded root is the root which is expanded by the current player's move.
A bounded root is a root which has lost all of its liberties.
If the expanded root is bounded, then the expanded root is removed from the board. If the expanded root and additional roots of either colour are simultaneously bounded, then the expanded root and only the expanded root is removed from the board. Removing the expanded root effectively undoes the move, and roots which were temporarily bounded are now freed. An example with White to move:

9
8
7
6
5
4
3
2
1
	a	b	c	d	e	f	g	h	i

Placement of a white stone at 1 expands the white root in the upper left corner. This move simultaneously bounds three roots: the expanded root, the black root in the lower left corner, and the white root in the lower right corner. White must immediately remove the expanded root, and only the expanded root.

If a player's move bounds one or more roots of either or both colours, and the expanded root is not one of the bounded roots, the player must immediately remove all of the roots which were bounded by that move.

9
8
7
6
5
4
3
2
1
	a	b	c	d	e	f	g	h	i

With this slightly different board, placement of a white stone at 1 expands the white root in the upper left corner, and the expanded root is not bounded. However, two other roots are bounded by this move: the black root in the lower left corner, and the white root in the lower right corner. White must immediately remove the two bounded roots.

At the conclusion of a turn, there should not be any bounded roots on the board.
Play alternates until only one player has roots remaining; that player is the winner.

The official starting configuration of a 19x19 board is as follows: