DVONN

DVONN is a two-player strategy board game in which the objective is to accumulate pieces in stacks. It was released in 2001 by Kris Burm as the fourth game of the "GIPF" Project. "DVONN" won the 2002 International Gamers Award and the "Games" magazine Game of the Year Award in 2003.
Rules.
Equipment.
"DVONN" is played on a board with 49 spaces. The board has a hexagonal layout 5 hexes wide. One player has 23 black pieces to play, the other player has 23 white pieces. There are also 3 neutral red pieces, called "DVONN pieces".
Object.
The object of the game is to control more pieces than your opponent at the end of the game.
Placement phase.
The game starts with an empty board and proceeds in two phases. During the first phase, the players place their pieces on the board, starting with the three red "DVONN" pieces. Pieces can be placed on any unoccupied space. White starts, and the players alternate. So Black is the first to place a piece of his own color. The first phase ends when all pieces are placed on the board, filling it completely.
Movement phase.
The second phase involves the building of stacks of pieces (a single piece is also considered a stack) by moving stacks onto other stacks. A stack is controlled by a player if his color is on top. A stack is immobile if it is surrounded by 6 neighboring stacks. The white player has the first move in this phase. Any mobile stack of height "n" (with "n" > 0) can be moved (in a straight line) in any one of the 6 directions by exactly "n" spaces by the player controlling it, if it lands on another stack. Jumping over empty spaces is allowed, as long as the tower does not land on an empty space. Single "DVONN" pieces cannot be moved, but they can be once they are part of a stack. After each move, all stacks that are not connected via a chain of neighboring stacks to any stack containing a "DVONN" piece are removed from the board.
Passing and game end.
A player who has no legal move must pass, and a player may only pass when no legal move is available. The game ends when both players have no legal moves. All stacks controlled by one player are collected into one tower. The winner is the player with the higher tower. The game ends in a draw in case both players own an equal number of stones in their tower. The maximum possible number of moves in the game is 97 (49 for placement and 48 in play, passes are not counted).
In competition, each player typically gets 15 minutes for the entire game in real-life tournaments, or 10 minutes for online tournaments.
Strategy.
The rules of "DVONN" can be learned in a few minutes. The main factor needed to win is to be in control of the game. The basic strategy of the game is given on the "GIPF" Project website. The more advanced strategy tips are derived from the general strategy guidelines developed by the DVONN guild at the BrettspielWelt game site. In 2003, 2004, and 2008 the game developer, Kris Burm, organized a real life DVONN world championship.
Placement phase.
Many beginner players place their pieces at the start of the game without a clear objective. However, placement is as major a factor in winning as the movement phase. While it is not possible to guarantee victory with a strong setup, it is possible to have no chance of winning by placing your stones badly.
Pieces should be placed with three main goals in mind: spaces by "DVONN" pieces, spaces by the side, and general density. The first objective is to place pieces by "DVONN" pieces, thereby keeping them safe from potential separation. Keeping at least three pieces by each "DVONN" piece helps defend them from potential attack. Next, pieces that are surrounded cannot move; therefore, having pieces along the side to start the game is valuable. Such pieces should also be in position to free other pieces on the inside. Finally, lumping groups of one's own pieces together is usually poor strategy. It is desirable to capture on every move, or at least take a "DVONN" piece; keeping all of one's pieces together often makes this difficult. Spreading pieces out across the board also increases the chance of maintaining a short (and therefore highly mobile) stack into endgame, where it may be moved into position for a crucial capture.
It may also be possible to string a line of one's own pieces across the board up and down. Play almost always separates along this line; pieces on one side of a string that has no "DVONN" piece are usually doomed. An additional advantage of placing stones connected in a line is that moving a stone on either end of the line will free another own stone for movement.
Having an even distribution of the "DVONN" pieces over the board is usually recommended for novice players, since this way they will be less vulnerable against groups of stones being lost by a cut off. Having all 3 red "Dvonn" pieces grouped together near the edge almost guarantees a win for an experienced player playing with white.
Movement phase.
The first few moves should correct any place where your position must be fixed: helping or moving pieces that could become isolated and moving outside pieces in order to give inside ones mobility. To go for a victory, one should try to recognize if it is possible to isolate part of the board from all the red "DVONN" pieces in such a way that the isolated part will contain more of the opponents stones than your own. Preferably, always play stones towards the "DVONN" pieces rather than away from them.
Capturing pieces that could capture a "DVONN" piece can be important, as a moving "DVONN" piece controlled by the opponent can isolate a large group of pieces. However, mobility is the most important aspect of "DVONN"; one needs to keep one's options open. Building a tall stack early in the movement phase is a mistake. Most often, the game is won by the player who is capable of making the last move(s). Maintaining some single stones until the end phase is, therefore, very often a good strategy. As a general rule one can state that using a tower to take a single stone of the opponent usually is one of the better moves, since this preserves own singles. A second general rule for selecting which move to make is that you should not make a move that the opponent cannot prevent you from making at a later time.
A very common mistake among beginners is that they are stacking own stones on top of each other in an attempt to prevent losing stones by being cut off by the opponent. However, since the game is all about mobility, this usually is a bad thing, since by stacking two of their own stones, instead of capturing an opponent's stone, they are effectively losing one stone. Only when a really large group of own stones is at risk, or in the end-phase of the game, should one consider placing own stones on top of each other. In any other situation, it is better to just give up the stone(s) in risk of being isolated and play offensive moves elsewhere and make the opponent lose a similar or preferably larger number of stones on another part of the board.
Taking a "DVONN" piece is especially desirable if it is possible to move it toward one's own pieces and away from one's opponent's. However, every capture counts, so big captures and maintaining mobility is more important than just taking "DVONN" pieces. A similar rule applies here as is the case for placing own stones on top of each other. When a "DVONN" piece is taken, the opponent is not losing a stone, which means that effectively you are set back one stone in the stonecount compared to the opponent. Therefore, one should take a "DVONN" piece only if one has a plan with it to gain a larger advantage, or if one needs to prevent the opponent from gaining a significant advantage by moving it.
After move 70 (about 20 moves into the movement phase) the board clears and settles. It becomes much more important to look ahead to see how every move affects the overall situation. Tall stacks are very hard to move, so they should be formed next to (or on) "DVONN" pieces and out of line of potential captures.
Strategy terminology.
"DVONN" strategy discussions among expert players often use a number of terms to express the game situation. In the Yahoo Gipf discussion group the development of this list of terms was initiated by Alan Kwan and completed by Kris Burm.
Dvonn playing computer programs.
There are many computer programs capable of playing Dvonn at a high level. Some of the early ones include:
RoRoRo the Bot and Jan's program used to play online at the LittleGolem games site until 2014 and 2016 respectively, and were usually among the top 10 players.
Holtz is a program supporting multiple games, including Dvonn.
Dvonn was the topic of the 2011 CodeCup which produced many high-level computer players, including contest winner PrimaDvonna.