THE MOKU FAMILY
Traditional Games and Modern Variants
(with collaboration of Edward Jackman and Bill Taylor)
N in-a-row games (win by making a line of N connected stones) seem to appear
independently in different cultures, which is not very common to abstract games.
This page includes many games, old and new, and are divided by the size of the
winning sequence.
ROWS OF 3
The most basic game of this family, played by most children, is Tic-Tac-Toe played in a 3x3 board:
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It's easy to see that this game always end in a draw, with reasonable moves.
Some more complex variants indexed here at WAG: 3 Musketeers, Dara, Wali, Neutreeko, 3 Stones, Winkers, and 4D TTT,
Another variant from Richard Hutnik (c) 1995, is Dual Tic-Tac-Toe: Select a board with size NxM (N>2 and M>3). Each player drops a stone of either color on an empty cell. The first player that makes a (orthogonal or diagonal) 3 in-a-row of either color wins. If the board gets full with no 3 in-a-rows, the game is a draw. Some variants are possible: Misère (who makes a 3 in-a-row loses), use more than two colors, more than two players...
A 1985 variant called King by Jim Wilkinson, uses six pieces (three of each color) with a setup phase where both players alternatively drop their stones into empty cells (the first drop cannot be at the center). After all pieces are on board, players move one piece per turn into a (diagonal or orthogonal) adjacent empty cell until one of them make a friendly 3 in-a-row. There is a move exception in the rules: "except diagonally black-to-black" which may only make sense with a view of the board (which I do not have).
There are several 3 in-a-rows in 3D (also check Qubic in the next section). Two of those are 1972's Rex and 1978's Trio. In Rex, there are three set of three columns where it is possible to drop up to 3 pieces (of either color) on each. Wins the player that achieves the first 3 in-a-row (either vertically, horizontally or diagonally in 3D). In Trio, the board is a 3x2x3 column pattern:
o o o
o o
o o o
both players try to achieve as many 3 in-a-rows possible, winning the player with the largest number.
Shift TicTacToe is a 1988 variant where: Two players play Tic-Tac-Toe on a "Connect Four" type board (meaning placing a disk sends it to the bottom first). On their turn, a player can drop a disc in, or slide a row one space to the left or right. Since the board is a 3x3, slides can sometimes send pieces out of the unit and back into regular play. The first to achieve 3-in-a-row is the winner.
Flip Tic-Tac-Toe (a 2006 game by Stratagem Publishers) is played on a 4x4 board with 64 stackable stones (4 colors with 16 stones each which I assume allows 2-4 players). Players are able to drop friendly stones (on empty cells or increasing stacks already on board), can move stacks (orthogonally to empty cells?) and also flip an entire stack (the bottom becomes to top). The goal is to make a 3 in-a-row of your own color.
Crosso is a 1975 game by C.S.Elliot: One player is the attacker, the other is the defender. The attacker draws crosses, while the defender draws circles. The attacker creates orthogonal or diagonal alignments of three or more crosses. The defender tries to prevent these alignments without creating alignments of their own. At the end of a round, the attacker scores 1 point per each 3 in-a-row (of either color), 2 points for 4 in-a-row, and 3 points for 5 in-a-row. At the end of the second match, the player with the most points wins.
In Nought-or-Cross
the current player
decides what type of piece the next player places. Wins the player that makes a
3 in-a-row of either color.
Shisima
is a 3 in-a-row
from Kenya (cf. wikipedia)
that was commercialized as
Tri-Pin.
Players take turns moving a piece to an adjacent empty point. Repeating a
position three times is a draw.
Another African traditional game is
Bolotoudou
:
This game starts with an empty board. Each player has 12 stones. At the first stage, players take turns placing 2 stones on empty squares. At this stage it's forbidden to put 3 stones of the same color in a row. After all the stones are put on the board, the players take turns moving their stones. The stone can be moved to an empty adjacent square vertically or horizontally. When 3 stones are arranged in a row, the player can remove from the board one of the opponent’s stones, which is adjacent to this group on the side. On the next turn, the player must move one of the stones of the same group. If a player has less than 3 stones left, he loses. ref
ROWS OF 4
There are several games that use 4 in-a-row.
The most famous is Connect 4. Also indexed here are Contigo, Delta, Firedrill, Gravity, Magneton, Complica.
One well-known variant, called Qubic (Parker Brothers, 1965) is played in 3D on four 4x4 boards, winning the first to make a 4 in-a-row (this game has other names, like Tramp).
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Both Patashnik (around 1980) and, independently, Louis Victor Allis and Patrick Shoo (around 1991) solved Qubic (first player win). Allis also solved Connect-4.
Quintego is a Connect-4 variant (with 5 columns): when a vertical column has six stones, and another stone is added, the bottom stone is removed and returned to the player's reserve (and all the others on that column move down). A previous name for this game is Complica.
Another interesting variant is Gigamic's Quarto. In this game, there are 16 different pieces (all combinations of 4 boolean features: high/low, round/square, light/dark and solid/hollow). A player drops a piece on an empty cell and selects the next piece which must be dropped by the opponent! The first player to make a 4 in-a-row of any of the 4 features, wins.
This game can be played with the following 16 stacks, where each feature is given by the color of a stone at a certain height.
An uninspired 4 in-a-row is Pentana, which adds a winning condition of occupying all four corners of a 4x4 board (pieces start at the player's first row, and move like a Chess king). The goal is to get 4 in-a-row orthogonally or diagonally on any row other than your starting row OR to get all your pieces placed in each corner.
A nice three player variant can be played (on a Go board) with the addition of the following rule: each player is obliged to block a winning threat of the next player.
| An 3 player example
With the next-block rule it's easier to be aggressive, knowing the next player's move may be partly restricted. The player just needs to force a win (e.g. a simultaneous double-open 3 and another 3).It is very dangerous to make a single-ended 3, because if the next player has a double-ended 2, he will extend it to 3, leaving the 3rd player compelled to block the 1st, so then there is only one player left to block the double 3. In the left diagram (white-black-red turns), Black should not play at [1] since Red drops at [2], then White is obliged to block the black 3 in-a-row and Black can only block one side of the Red's already winning line. |
Delta
is a 1975 game by
Erich Brunner. Mats Winther's words:
The object is to form a line of four, either diagonally or orthogonally. Stalemate is loss. Players have nine stones each. The board is 5 x 5. White moves first.
Players first drop a stone each. Then they take turns to make make double-moves. First, the player slides a stone, diagonally or orthogonally. (A slide move must be longer than one step.) After the slide move, the player must drop a stone on the last square slided over. The first stone moved is called “forerunner”. The second is called “follower”.
In the opening phase, the second player may forfeit his first slide move (by pressing the red button) and make only the drop move. (This is the only time that pass is allowed and serves to equalize chances.) When all nine stones have been dropped, you must instead relocate any of your stones on the board (except the one just moved) to the last square slided over. ref
Ten-Q is played on a 7x7 board and the goal is to make a 4 in-a-row or a diamond 2x2 shape pattern.
Tabou by Michel Brassinne, appeared on Jeux et Statègie #28 in 1984.
The translation:
Material: Ten black stones or pebbles for one player; ten white ones for the other. The playing area is a 6 × 6 grid drawn on the sand.
Objective of the game: To achieve an alignment of four stones of one’s color, either vertically, horizontally, or diagonally.
Players take turns, starting with white. Each player places one stone on an empty square of their choice.
Once all stones have been placed, the swapping phase begins.
In turn, following the same order as placement, each player can swap the position of two stones of different colors.
To perform this move, the two stones of different colors must be adjacent (horizontally, vertically, or diagonally).
The opponent is not allowed to move any stones that were swapped in the previous turn—these stones are taboo!
The player who manages to align four stones of their color scores a point. A new game begins. The winner is the first player to reach five points.
[Illustration caption]: The black player swaps *a* and *b*, aligning four of their pieces.
Canoe is a 2003 game by Dale Walton, where the player must make a 'canoe', a bent 4 in-a-row. Here are the rules:
Exago is a 2004 game by Mark Forsyth, is played on a hexagonal board of size 6, where players drop a limited number of pieces (twelve), then reuse them, moving any friendly piece to another empty hex. If a group is surrounded, it is captured and returned to his owner, to be used again. The first to have four pieces in a straight line wins the game..
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ROWS OF 5
Perhaps the most famous 5 in-a-row game is GO-MOKU, an ancient Japanese game. The full name, "Go-moku Narabe," literally means "five stones in a row." In Japan, a more complex version of the game exists, known as Renju. Check more information at playSite. Victor Allis' Thesis presents the solution of Go-moku (first player wins).
The game starts at an empty Go board.
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| An example
Black's turn. White has a winning position at the three cells [1]. |
Murray in his book A history of board-games other than chess refers another set of rules (game 3.7.1) consisting of two phases. First a drop phase where both players drop an agreed number of stones, then a move phase where each player moves a friendly stone into an adjacent (orthogonal) empty cell. Win by making an orthogonal 5 in-a-row. A similar variant (using twelve stones) states that each time a (orthogonal or diagonal) 5 in-a-row is achieved (in the drop or move phase), the player removes an enemy stone. The player which reduces the adversary to four stones, wins the game.
A
traditional variant called Gomoku-Ninuki adds an extra custodian capturing rule:
two enemy stones are captured when placed between two friendly stones, and a new
winning condition: a player also wins by capturing 10 stones. This game is also
known as Check-ro
(1957) and Pente
(1977). Bolix, aka
Bollox,
is a similar variant played on a 5x10x5 hexagonal board, but where only one of
the two enemy stones is captured. Also 1973's Keryo-Pente
,
by Rollie Tesh, allows for the capture of two or three stones. Another
commercial game is Wu
that comes with a 19x19 board and has three 'levels' of play: the first is
Gomoku, the second is like Pente but without removing the 'captured stones'
(they stay on board), and the last is just using sand-timers for time-control.
In the end of the XIXth century, Japanese players started to change Go-moku and tried to create a more balanced game (the first player, Black, has a tremendous advantage) which they called Renju (read the game's history). This was done by creating some restrictions in Black's move, namely:
- Black cannot create a 2 open 3 lines (and so winning)
- Black cannot create a 2 closed 4 lines (and so winning again)
- Black cannot create an overline (i.e., 6 or more stone line)
- Black's 1st move is a the center board, and Black's 2nd move must be at cell distance greater than 2.
- White's 1st move is decided by Black.
- At White 2nd move, there is the PIE rule: White may decide to change sides!
For more detailed information, check the international rules of Renju maintained by RIF: The Renju International Federation (some variants are also shown).
There
are a lot of variations of this simple game. Daedalus
is Gomoku in an
hexagonal board. A curious crossover between Gomoku and Reversi, called
Gomullo
invented by Roland Johansson at 1999 and can be defined as: wins who gets N
stones in-a-row in a NxN-board, using the rules of Reversi. Another variant,
with shifting rows, is Perplexus,
where the player may drop a stone or shift a row one cell to the right or left
(with 6 sliding rows of 7 stones placed within a base row of length 11).
Some comments from Edward Jackman: Here's a list of modifications we've used to address first player advantage and handicapping:
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Another game from Edward (around 1995) is Progressive Gomoku: Black starts by dropping one stone, then White drops two, then Black drops three... There is, however, one restriction: during a drop sequence, all the stones must be mutually non-adjacent (i.e., they cannot be adjacent to each other).
Applying the progressive mutator (drop one stone at the first move, then drop two, then drop three...) to Gomoku also provides a very enjoyable game, if we add a restriction: No two stones in a turn may finish in the same group (i.e., a set of friendly stones orthogonally or diagonally connected). If a fast game, but with lots of tactical subtleties. This game should be played on an unlimited board.
| An example
White's turn. This is the 8th move, so White can drop eight stones. However, it is enough to drop four (the marked stones). After that sequence, Black cannot stop the double attack at cells [1] because it would violate the restriction (two stones on the same group). |
The next game was designed by Bill Taylor and is called QUAD-MOTU:
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Here's a match example on a hexagonal board:
5 HEX-MOTU (one optional move step + one mandatory drop)
==========
abcdefghijklmnopqrstuvwxyzABC Billx Joao
-----------------------
1 . . . . . . . . 1. --- o8 -- p7
2 . . . . . . . . . 2. --- n7 -- p9
3 . . . . . . . . . . 3. o8-m8 o6 p9-n9 p5
4 . . . . . . . . . . . 4. n7-o8 l9 p7-n7 k8
5 . . . . . . . o . . . . 5. o8-q8 p7 n9-o8 r9
6 . . . . . o x x x x x . . 6. l9-n9 p9 p5-n5 o10
7 . . . . o x o . o . . . . . 7. p7-q6 s6 n5-m6 r7
8 . . . . . . . o x . . . . . . 8. m8-l7 t7 k8-j7 r5
9 . . . . . . x x o . . . . . 9. t7-u6 w6
10 . . . . . . o . . . . . . 10. 1-0
11 . . . . . . . . . . . . 11.
12 . . . . . . . . . . . 12.
13 . . . . . . . . . . 13.
14 . . . . . . . . . 14.
15 . . . . . . . . 15.
These rules define a more "violent" game. This extra freedom may provide a solution to the drawish feature of gomoku in hex boards.
Drop and Move Gomoku gives each player just 12 stones. After the drop phase, the move phase begins: each player moves one stone to an adjacent (orthogonal or diagonal) empty cell. Wins the player that makes a 5 in-a-row.
Tomas Flodén designed Pentago, a 5 in-a-row game where a 6x6 board is made out four separate 3x3 boards. Each player, on his turn, drops a friendly stone on an empty cell and then rotates one of the four small board 90 degrees in any direction (i.e., clockwise or counterclockwise). If all cells are occupied before a 5 in-a-row is achieved, the game is a draw. Also, if due to a rotation, both player get a 5 in-a-row, the game is also a draw. This idea suggests a hexagonal variant, where each cell on the board could be select as a pivot to rotate the adjacent 6 cells in either direction (a physical board would be difficult to make, it would be better to play this variant on a computer).
A 2005 game which also tries to balance first player
advantage without protocol moves is
Vincent Everaert's
In
Love Gomoku
.
On each turn, each player drops a friendly stone on an empty cell and then an
enemy stone on an adjacent empty cell. If there is no additional empty cell to
drop the enemy stone, the turn is invalid. As usual, a friendly 5 in-a-row wins
the game.
| An example
[puzzle by the author] Black wins in two moves. How? Answer: 1.h6,g5 forcing White to reply g6,h5 and winning with h8 (select this line) . |
João Neto and Bill Taylor tested this variant and found the game is not decisive. Here's a match played on an unbounded board, until we decide to stop due to the fact that neither player was making meaningful threats:
___Bilx________Joao___ ___Bilx________Joao___
1. n26 m25 m24 l23 10. i25 i26 h24 g25
2. m26 n27 l26 k26 11. i24 j25 k22 j21
3. k24 j24 k25 j26 12. i21 j20 k21 l20
4. m27 n28 n24 n23 13. k19 k20 n22 o21
5. o23 o22 p23 q22 14. l22 m21 f l19 k18
6. l28 k28 o25 p25 15. q23 r22 m20 n19
7. k27 l27 m29 m28 16. o20 n20 m18 m17
8 m23 l24 k23 j23 match stopped
9. o24 n25 m22 l21. . . . . . . . . . . . . . 16
. . . . . . . x . . . . . . 17
. . . . . x . o . . . . . . 18
. . . . . x o . x . . . . . 19
. . . . o o x o o x . . . . 20
. . . x x o x o . x . . . . 21
. . . . . o x o o o . x o . 22
. . . . x o x x x x o x . . 23
. . o x o x o o o x . . . . 24
. x . x o o . o o o x . . . 25
. . . o x x o x x . . . . . 26
. . . . . x o x o . . . . . 27
. . . . . o x x o . . . . . 28
. . . . . . . o . . . . . . 29
. . . . . . . . . . . . . . 30
f g h i j k l m n o p q r sSince the 5-moku was seemingly too difficult to achieve, a 4-moku was tried. Here the problem was the opposite, too easy to finish:
___Joao________Bilx___
1. l20 l19 k19 k18
2. m19 n20 n18 o17
3. i19 h19! <-- this move forces a zugzwang. . . . . . . . . . . . . . 16
. . . . . . . . . o . . . . 17
. . . . . o . . x . . . . . 18
. . o x . x x o . . . . . . 19
. . . . . . o . x . . . . . 20
. . . . . . . . . . . . . . 21
f g h i j k l m n o p q r ssidenote: The idea that motivates In Love Gomoku can be made a mutator and applied to other games, like In Love Y, which is a reasonable playable connection game. In Love Go, otoh, also does not seem to work that well.
Philip Shoptaugh's Challenge 5, aka, Interplay (from 1980): there are narrow and wide stones, and wins by making one of three alternate patterns (N-W-N-W-N, N-W-W-W-N or N-N-W-N-N). There are three different types of pieces: a narrow cylinder, a wide cylinder, and a wide tube. The narrow cylinder will fit inside the wide tube, and so those two pieces can share the same space - but only if they belong to opposite players. Pieces may also be moved, once there are no more new ones to be placed.
Shintai is a 2009 variant by Steve Metzger where at every fifth move the player, instead of dropping a stone, relocates a friendly stone already on board.
The next picture shows the rules of Joshua Howard's Bones (1994):
Bango is a 2003 game by Steffen Mühlhäuser. There are 16 tiles for each one of two colors, and no board. Players drop tiles orthogonally adjacent to dropped tiles (must share an edge, a corner is not enough). If no 5 in-a-row (orthogonal or diagonal) is reached after all 32 pieces are dropped, players take turns picking one friendly tile and moving elsewhere in the playing area (again adjacent to another piece). It is illegal to pick a tile that would split the group.
Neumoku is a 2004 game by João Pedro Neto and Bill Taylor, where the neutral mutator of Nex is applied:
- Same as Gomoku, except that each player either:
drops a friendly stone plus a neutral stone
flips two neutral stones into friendly stones and then flip another friendly stone into a neutral stone
Pie rule: after the third move, the second player may swap sides.
A sample game:
--x----?-----o----?--
1. n3 m5 o2 n4
2. l6 q2 o3 p2
3. o4 p5 m2 q1
4. n2 n6 n4p2 o2
5. q1o2 n2 p4 q5
6. n2q5 n3 p3 m3
7. n3p5 q5 p1 q3
8. p0 q6 q5q6 p3
9. l4 k5 m3q3 p2
10. p2q2 q1 r2 r3
Actual Board:
j k l m n o p q r s
. . . . . . . . . . -1
. . . . . . x . . . 0
. . . . . . o ? . . 1
. . . o x x x x o . 2
. . . o x o ? o ? . 3
. . x . o x o . . . 4
. ? . ? . . x o . . 5
. . x . ? . . o . . 6
. . . . . . . . . . 7
Here, 'o' has a winning sequence:
--x---?-----o---?--
11. o5 l5 r7 s1
12. s7 l3 q4 t0
j k l m n o p q r s t u
. . . . . . . . . . . . -1
. . . . . . x . . . ? . 0
. . . . . . o ? . ? . . 1
. . ? o x x x x o . . . 2
. . . o x o ? o ? . . . 3
. . x . o x o o . . . . 4
. ? ? ? . x x o . . . . 5
. . x . ? . . o o . . . 6
. . . . . . . . . x . . 7
. . . . . . . . . . . . 8
Qui Vive
, by Eugene de
Wolf, uses five pieces
per player on a 5x5 board, trying to make one of five different shapes (lots of
fives!).
. . . . . . . . . . X . . . . . . . . . . . . . .
. . X . . . X . X . . X . . . X . . . X . X . . .
. X X X . . . X . . . . X . . . X . X . . X . . .
. . X . . . X . X . . . . X . . . X . . . X X X .
. . . . . . . . . . . . . . X . . . . . . . . . .
Chicken Gomoku applies the auction rule to balance asymmetrical games. In this case, Black must make 5 in-a-row in a 9x9 board (which is basically impossible), while White tries to prevent it. The auction will provide players the chance to drop black stones until the first player decides to take the role as Black.
- Same as Gomoku, except:
- Played on a 9x9 board
- Black must make a 5-in-a-row, White must prevent him.
- Both players play black moves until one declares to be black, simultaneously passing.
- Then alternation as usual starting with White.
Here's some matches of this surprisingly good variant ('f' means forced move):
a b c d e f g h i 0. J starts: e5, f3, h9, B takes
. . . . . . . . . 1. e4 d5 10. f3 f b3
. . . o o x x . . 2. c5 d4 11. a3 f h5
o x x x x o x . . 3. f6 d6 12. f5 f h4
. . . x o o o x . 4. d7 g3 13. h6 Black resigns
. . o x x o x x . 5. f4 g2
. . . x o o . o . 6. e2 g5
. . . o . . . . . 7. g4 d3
. . . . . . . . . 8. d2 f c3
. . . . . . . x . 9. e6 e3
a b c d e f g h i 0. B starts: e5,h1,f2,h9 B takes
. . . . . . . x . 1. f4 e3
. . . . o x o . . 2. d4 e4
. . x . x x . . . 3. e2 e6
. . . o x o . . . 4. e7 f d5
. . . x x o . . . 5. f5 f3!
. . x . x . . . . 6. g2 f f7
. o . . o x . . . 7. g8 f c6
. . . . . . o . . 8. b7 f c3
. . . . . . . x . 9. White resigns
a b c d e f g h i 0.
. . . . . . . . . 1. B starts: d3,h8,a9 J takes
. . o . x . . . . 2. d6 c4
. . . x o x . . . 3. b5 e4
. . x . x o . . . 4. f4 f5
. o . x x x o x . 5. c2 h7
. . . o x . o o . 6. g6 h5
. . . . o o . x . 7. h6 e5
. . . . . . . x . 8. g5 e6
x . . . . . . . . 9. e2 e3 f
10. e7 d5
11. f7 f3 & Black wins in two moves
Other games indexed at WAG: Andantino, Kassle, Quixo, Campaign, Ergo, Pentagonal 3D5 and Hex-gomoku.
ROWS OF 6
Games with more than 5 in-a-row need extra liberties to avoid easy draws (it's much easier to block a player in a regular board). One possibility is to add the 1222 progressive mutator: In each turn, each player drops two stones (except in the first turn, which balances the game).
| An example
The marked black stone has coordinates (0,0). All the other drops are relative to that first one (this notation is used because the board is not limited). 1. 0,0
1,0 1,-1 |
This game is, at least, from 1993, and is now known as
Connect6
. The game has the advantage of
partly nullifying the
opening advantage by 1222 play. Bill Taylor thinks it is a forced win, but has
no idea to whom! In practice games tend to be a similar length to normal Go-moku.
There is a 1983 game, Jargen Hagedorn's Hexago to make a 6 in-a-row on a large hexagonal board, however, with no additional rule, this simple goal cannot be done.
Pentello is a 2009 game by João Neto and Bill Taylor:
Player A places two black and one white stone on an infinite board. Player B choose colours; then play continues alternately with
white playing the next stone. If two stones of the same colour become trapped by a newly-played and an existing stone of the other colour, their colour is changed. First to make a ortho/diag line of six (or more) stones wins.Here are some matches:
i j k l m n o p q r s Jx Bo
. . . . . . . . . . . 1 k5 n6
. . . . . x x . . . . 2 o7 n7
. . . o . x X . . . . 3 m5 n5
. . . . x . . . . . . 4 m6 p5
x o o o o o x o . . . 5 o6 l6
. . . o o o x . . . . 6 n8 n3
. . . o o o x . . . . 7 n2 l3
. . . . . x . . . . . 8 o5 m4
. . . . . . . . . . . 9 o2 m7
. . . . . . . . . . . 10 l5 j5
. . . . . . . . . . . 11 i5 l7
. . . . . . . . . . . 12 o3 & wins after o4, q6i j k l m n o p q r s Bx Jo
. . . . . . . . . . . 1 k5 n5
. . . . . x . . . . . 2 o7 m7
. . . x . x . . . . . 3 l5 l7
. . . x x x x . . . . 4 m6 n7
. . x o o x o . . . . 5 n6 o6
. . o x x o x . . . . 6 m4 l6:
. x . x o o o o o x . 7 l8: n3
. . o x . . . . . . . 8 p7: q5:
. . . . . . . . . . . 9 j7 m5
. . . . . . . . . . . 10 l4: q7:
. . . . . . . . . . . 11 r7 o5
. . . . . . . . . . . 12 o4 n4:
13 l3: k8
i j k l m n o p q r s 14 n2: resign!
A "bent moku" game is Corners by Stuart Elliott. Here a review from Games and Puzzles #73:
Check also Freeling's Hexade.
ROWS OF 7, 8, 9...
There is a proof that 9 in-a-row games is a draw even on infinite boards and 8 in-a-row is almost proved. No one has a clue about 6 and 7 in-a-row (perhaps a win and draw, respectively)
Kokto, by Les Jeux du Pige, is a 8 in-a-row variant where after the first player plays at the 19x19 board center, the next player must place one friendly stone on an empty cell (orthogonally or diagonally) adjacent to any other stone, and the second stone adjacent to the first one. This means a player cannot start by placing a stone where there are no empty adjacent cell.
OTHER ROWS
ShanJari, a 2003 game by Kevin Brougher, is a moku game with shared stones of four different colors (the board is a large 13x16 rectangle of hexagons). Both players agree on a certain pattern (eg, red-blue-yellow-green-green) and both try to make it. The first player that notices the winning pattern wins. The pattern must be of any size and color combination.
However, imho, it seems that each player should have his own sequence (or equal size) so the game would become more strategic.