Margo is a board game similar to Go, played with marbles which may stack upwards. A special capture rule means that pinned pieces survive capture as zombies.

New Book! Margo Basics Margo Basics provides a comprehensive look at the game through examples, puzzles and annotated sample games. Get the print version here or a free download here.

Rules Equipment: The board consists of a 7x7 square grid of holes. Two players, White and Black, each have at least enough marbles of their colour to cover the board. Start: The board is initially empty. White places the first piece at any board point, then Black may elect to swap colours in lieu of making the next move (swap rule). Play: Players then take turns placing a piece of their colour either:            1) at an empty board point, or            2) stacked on top of four existing pieces (of any colour). Players may not pass.

Figure 1. Starting position.

Capture: After each move, all enemy groups without any board-level freedoms (connected empty board points) are captured and removed from the board, as in Go. For example, move a captures the following White group.

Figure 2. Surround capture.

Move b does not capture the following White group as it still has two board-level freedoms after the move (marked *). The stacked piece allows this group to temporarily escape capture.

Figure 3. Board-level freedoms keep this group alive.

Pinned Pieces: When a group is captured, any of its pieces pinned by higher-level enemy pieces remain in place. For example, move c captures the following White group but leaves two pinned pieces.

Figure 4. Pinned pieces are not removed.

Pinned pieces remain active in the game and can play an important role.

Over/Under Rule: A connection crossing over an enemy connection cuts it. For example, Figure 5 shows a White group cutting the connection between two Black pieces. Each group therefore consists of a visibly connected set of pieces when viewed from above.

Figure 5. The White overpass cuts the two Black pieces (over/under rule).

No Suicide: It is not permitted to place a piece without freedom, unless that move captures neighbours to create its own freedom.

Ko Rule: It is not permitted to repeat the board position of the previous turn.

Aim: The game ends when the current player has no legal move. The player with the most pieces in play wins (draw if equal).

Examples

Figure 6 shows a larger 9x9 game in progress. White currently leads on piece count, however Black commands more board-level territory and will soon overtake White as the game enters the eye-filling stage (explained in the Strategy and Tactics section below).

Figure 6. A 9x9 game in progress.

Any piece with another piece directly above it hiding it from view is described as buried. Buried pieces do not count in any connection but are counted in players' scores. For example, Figure 7 shows two White groups separated by a single Black group (left) and two Black groups separated by a single White group (right). In both cases, the central piece is still visible even though it has four other pieces stacked upon it, and is a connected part of the respective group. Placing a piece at the apex of this stack would bury the central piece.

Figure 7. The central pieces are visible and hence connected.

Zombies

One of the main differences between Margo and Go is the presence of zombies, i.e. pieces saved from capture by a pinning enemy piece. They are called zombies as they have been technically killed due to lack of freedom, yet remain alive in the game. Many (most?) games are decided by zombies, and the urge to build upwards to establish strong connections is always tempered with the danger of creating enemy zombies.

The following example shows the power of zombies. Can Black save this game? Click on the image to see the answer.

Strategy and Tactics

As in Go, groups with a single eye are vulnerable to immediate capture and groups with two or more eyes are safe from immediate capture. Unlike Go, this safety may not be permanent since players cannot pass and may eventually be forced to fill in their own eyes.

Players' scores, being based on piece count, will be tied at the end of each round until a capture occurs. However, the fact that players may not pass means that at least one capture is more or less inevitable and ensures that most games will have a clear winner. Territory is therefore an important secondary consideration, as the player that commands the most territory in the end game is the most likely to survive an eye-filling race.

Stacking to Join/Cut: Stacking moves can be very powerful. For instance, Figure 8 shows how two vulnerable (single-eye) groups may be formed into a safe (double-eye) group with stacking move d.

Figure 8. Combining two vulnerable groups into a single safe group.

This ability to save vulnerable groups would have made stacking moves far too powerful, resulting in very few captures and dull games, if it were not balanced by the inverse ability to cut safe groups into vulnerable ones. Figure 9 shows how a safe Black group with two eyes (marked *) may be split into two vulnerable single-eye groups by a White connection cutting across it.

Figure 9. Cutting a safe group into two vulnerable ones (over/under rule).

Pinned Pieces: Stacking moves are strong in that the pieces they pin become fixed, unless the stacked pieces are themselves captured and removed. It is therefore good to stack on friendly pieces but players should think very carefully before stacking on enemy pieces.

For example, consider the situation shown in Figure 10 in which White would like to move at e to capture the leftmost Black group. This is not a legal move as the pinned Black piece would survive the capture to leave the White piece with no freedoms after the move. The higher-level (pinning) White piece is a nuisance to White in this case.

Figure 10. White cannot move at e (suicide).

The fact that pinned pieces remaining alive in the game means that they can be exploited to safely reduce enemy freedoms (as shown in Figure 10) or used as stepping stones to extend groups. They can also be used as bases for apparently suicidal incursions into enemy territory that suddenly become quite dangerous if the opponent can be forced to also pin the invading pieces.

Pinned pieces introduce subtle tactics foreign to Go and represent a fundamental difference between the two games. As the board fills up and players' territories become more clearly defined, it becomes pointless to play in enemy territory in Go except under certain circumstances. However, such territorial invasion can be a game-winning play in Margo if the attacker is able to keep the invading group alive long enough (typically using pinned pieces) to connect over the enemy wall to an existing support group. Even if such an invasion fails, the attacker can usually force the defender to pin at least some of the invading pieces and hence whittle away at valuable territory.

Edge Play: Adjacent pieces on the outermost row or column of any level cannot be cut, as it's not possible to bury them or separate them with an overpass (see Figure 11). Edge moves can therefore be quite strong despite the fact that the edge removes a potential freedom.

Figure 11. Black cannot cut the safe White group.

Notes

Counting pieces rather than territory to determine the winner makes scoring straightforward and avoids disputes over undecided territory.

The board size was originally 8x8. This led to deeper games wth greater scope for strategy, but also much longer cold phases when large volumes of the pyramid had to be filled in during the eye-filling stage. The 6x6 board is a nice balance between depth and practicality; it still provides a rich game, but avoids the long cold spells which are the least interesting aspect.

The Margo board, when fully stacked, forms a pyramidal or cannonball stacking. The maximum number of pieces that may be played on a board of size n is given by the pyramidal number Pn = n (n + 1) (2n + 1) / 6.

A game of Margo can therefore take several times as long as a game of Go on the same sized board. For example, an 8x8 Go board has room for 64 pieces whereas an 8x8 Margo board has room for 204 pieces (although these limits will rarely be approached). Also, the additional eye-filling stage of Margo will extend most games to an even greater extent.

36 pieces should be sufficient for each player in a standard 6x6 game, as Margo relies heavily on board-level play and pieces will not usually stack too high before the game ends. Some longer games may require more pieces (it can pay to have a few marbles on hand).

Like Go, pieces may have up to four adjacent freedoms. Unlike Go, pieces may have up to twelve adjacent neighbours.

The swap rule is used to discourage the first player from making an overly strong opening move.

Due to the no-pass rule, games typically enter an extended cold phase in which the players are forced to fill in their own eyes or make otherwise disadvantageous moves. This adds to the drama of the game, since the losing player may eventually turn the game around to force a win if they have managed their territory more cleverly than their opponent. Territory plays a more important role if passing is not allowed.

Variants

Single Capture: Players wanting a shorter game can instead award victory to the first player to make any capture. But the winning move still has to be a legal no-suicide move!

Multiplayer Version: Margo can be played by three or more players. Multiplayer Margo is played using the same rules as the two-player version, however a couple of clarifications are warranted.

Figure 12. Either a Black or Grey piece at m captures the White group, which has no remaining liberties.

Some multiplayer Go variants relax the connection definition so that enemy groups may consist of stones of any colour except the current player's. Margo maintains the stricter definition (that any group may consist of only one colour) to encourage captures.

Figure 13. The two Black pieces are cut by the combined White/Grey overpass (over/under rule).

History

Margo rules by Cameron Browne 2006 and copyright (c) Cyberite Ltd 2008.

The name "Margo" = Marbles + Go.

I'd been wanting to devise a practical 3D Go variant for years. Various attempts were made without success, mostly due to the fact that unconstrained freedoms in 3D make groups all but impossible to capture, leading to rather dull games. Games such as Tanbo3D get around this problem by constraining piece growth, but I wanted to retain Go's freedom of placement.

The simple innovation that finally yielded a workable game was to limit freedoms to the board level. In addition, the "don't remove pinned pieces" capture rule was found to avoid potential ambiguities with revealed connections and falling pieces, and to add tension to the game as stacking then became a two-edged sword.

Margo may also be played with the Akron-style movement of pieces from one point to another to add further dynamicism (perhaps too much?) However, the official rules do not allow piece movement as it effectively allows players to pass by making cycles of repeated moves. Such cycles can be avoided using a super-ko rule that forbids the repetition of any previous board position, but then things start to get messy. In addition, pieces that drop could have the undesirable side-effect of creating multiple friendly groups with no freedoms.

The default board size was originally 9x9 but this was found to lead to lengthy passages of cold play in which players were forced to fill in significant regions of the board following temporary deadlocks before the tension started to mount again. Reducing the default board size to 8x8 reduced the problem, although some cold wars would still occur involving large piles of balls. The 6x6 board size almost eleminates the cold war problem while maintaining significant depth, and makes each move more immediate and important, thus increasing the tension right from the start.

Margo can be played on Richard's PBeM server - check out the help file for more details.
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