Draft:Tribun pugna pro cannae

Tribun pugna pro cannae is a board game for two players. It is usually abbreviated Tribun or Tribun ppc.

Tribun is an abstract strategy game that involves no hidden information and no elements of chance. It is played on a tribunboard with 91 hexagons arranged into a greater hexagon with a side length of 6 small hexagons, following hexagonal tiling. The players, referred to as "White" and "Black", each control 35 pieces and 1 tribun. One player is chosen to make the first move, then turns alternate. The game is lost by ones tribun being taken or running out of legal moves. There are several ways a game can end in a draw.

The first Tribun prototypes were created around 2020 in Lower Saxony, Germany. And the finalization of the rules took until about 2022. Due to Tribun being rather new there exist no engines yet.

Rules
The rules of Tribun are published by the authors on their website Tribun.org under the Download Tab.

90% Rules
The 90% Rule set is a simplified version of the game that is used to be taught to beginners. It excludes the following (from harder to learn to easier to learn):
 * Impero and all changes that come with it
 * Symmetrical Combination
 * The Unit Centuria (8)

The following description of the rules contains all rules, but modifications or clarifications (to making a turn) will be made when Impero is introduced.

Unit
The unit is a stack of tribun pieces where the height is measured by the count of pieces. The height (counted separately for both players) determines the kind of the unit. Height directly translates to attack power and resilience against enemy attacks. The height furthermore changes the moving and attacking pattern of the unit. The names of the Units are as follows:

Servus (1), Hastatus (2), Saggitarius (3), Eques (4), Balista (6), Centuria (8)

Units can also be merged with the Tribun. The Tribun piece must always be the piece on top of the unit. The Tribun also counts toward the height of the unit and increases it by 1. Should the height of a Unit with Tribun equal one of the above heights then this unit inherits the same moving / attacking pattern and name with Tribun as suffix;

4 pieces = Eques, 3 pieces + Tribun = Eques Tribun.

The only exeption to this is a single Tribun piece. The according Unit has a height of 1 but is called the Tribun and moves differently compared to the Servus. Pieces with the height of 5, 7 and above 8 do not exist. There is no move to create these units as they are invalid.

Setup
Tribun sets usually have simple, stackable pieces but might include decorated Tribun pieces (can be stacked on top of usual pieces). Tribun pieces are divided into two sets, usually light and dark colored, referred to as white and black, regardless of the actual color or design. The players of the sets are referred to as White and Black, respectively. Each set consists of 35 pieces and 1 Tribun.

The game is played on a hexagonal board that is made from small hexagons and has a side length of 6 hexagons. By convention, the 91 hexagons alternate in color and are referred to as, and  hexagons. This is done such that the corners are colored white and black and no same-colored hexagons touch; common colors for chessboards are shades of brown.

The units are set out as shown in the photo, n numbers symbolize a tower of n pieces. Black's position mirrors White's, with an equivalent piece on the same file. The board is placed with a light square at the right-hand corner nearest to each player. The correct position of the white colored corner hexagon is in front of the white player while the opposite black colored corner is in front of the black player.

The Tribun (1) is positioned on the corner of the board (on a hexagon matching the color of the player). A Saggitarius (3) is placed directly above the Tribun and two others adjacend to it, such that the Saggitarii form a very slight u shape. Adjacend to all of them is a Hastatus (2). Next to the left Saggitarius 4 Hastati (2) are positioned such that the form an upside down 1 whilst touching the edge of the board and the left Saggitarius. This is mirrored to the other side. The Hastati that are furthest up the board each touch 3 Servi (1) such that these form a slight downward u. At last 1 Servus continues the line of Servi toward the side on both sides.

In competitive games, the piece colors and the beginning color are allocated to players by the organizers; in informal games, decisions are usually made randomly, for example by a coin toss, or by one player concealing a white piece one hand and a black piece the other, and having the opponent choose.

Turn
After the first player makes a move, players alternate turns. They may choose 1 of these for kinds of Actions: Moving 1 of their own units, attacking 1 enemy unit, disassembling 1 own unit or merging 2 (or more) own units together. Not moving - possibly due to having run out of legal moves - is considered a loss.

Moving
Every Unit has its own movement pattern, as illustrated by the diagrams. The diagram is relative with the Unit being at the center of the small board. Only Units that walk along arrows can (and will) be blocked if something occupies a target hexagon. They cannot jump over the blockade. The Units Hastatus (2) and Saggitarius (3) cannot be blocked which may result in them having to be lifted over other units.

Only empty hexagons that are on the movement pattern of the unit about to be moved can be walked upon. The entire Unit has to be moved to the destination.


 * The Tribun (1) moves to adjacent hexagons.
 * The Servus (1) moves one hexagon up or down the board (towards the opponent and never towards the player)
 * The Hastatus (2) moves one step on the same color and reaches one step further than the Tribun
 * The Saggitarius (3) moves to the opposite colors, one step further than the Hastatus
 * The Eques (4) moves just like the Hastatus, but can continue into the same direction until he is blocked
 * The Ballista (6) moves like the Eques
 * The Centuria (8) walks like the Tribun but can walk two steps unless it is blocked by an enemy Unit on the first step. It cannot walk to the hexagons a Hastatus could walk to.

Attacking
Every Unit has its own the attack pattern. The difference to the movement pattern is that the attack pattern can only be used on hexagons that are already occupied by the opponent.


 * The Tribun (1) attacks like it moves.
 * The Servus (1) attacks adjacent hexagons to the left and right to the hexagon he would walk to.
 * The Hastatus (2) attacks like it moves
 * The Saggitarius (3) attacks like it moves
 * The Eques (4) attacks like it moves
 * The Ballista (6) moves hust like the Tribun, but can continue into the same direction until he is blocked
 * The Centuria (8) attacks like it moves and also the hexagons a Hastatus could attack / walk to.

To attack, one of the opponents Units has to be chosen as a target. All own Units that can attack the target by means of their attack pattern have to be correctly identified. Now it has to be chosen which of the Units participate and which do not. Then the height / attack strength of all participating attackers is summed up and subtracted from the target.


 * If the target becomes illegal (5 / 7) one more piece  is taken.
 * If the target hexagon is empty one of the participating Units must replace the attacked Unit.

Decombination / Disassembly
This has nothing to do with the movement / attack patterns. One owned Unit is chosen (not a Tribun). All its pieces can be distributed over its former empty adjacent hexagons and the original hexagon.


 * No illegal Units (5, 7, >8) may exist at the end of the turn.
 * The Unit has to be distributed over at least 2 hexagons
 * No piece may be taken of the board

''Not all hexagons have to be used. Even the original hexagon can be left empty and there are no further constrictions on what units may be created. The Tribun may not Decombine.''

Combination / Merging
This has nothing to do with the movement / attack patterns. One empty hexagon is chosen. Now exactly two adjacent own Units are chosen. Now an arbitrary amount of pieces can be donated from both Units, the donated pieces are to be stacked onto the former empty hexagon.


 * If Tribun-Unit donated then this Unit must fully donate itself (will leave an empty hexagon), the Tribun must sit on top of the new formed Unit
 * No illegal Units (5, 7, >8) may exist at the end of the turn.
 * No piece was take of the board

The participating Units neither have to be the same height nor participate the same amount.

Symmetrical Combination / Merging
This is a special case of the standard combination, so only the differences will be highlighted. Instead of choosing "exactly two adjacent own Units" either exactly 3 equally spaced Units or all adjacent Units are chosen.


 * All chosen Units must be equal; any two Units could be swapped without changing the situation, they are of the same height, your color and not a Tribun.

All chosen Units donate the exact same amount. All of the conditions from the standard still apply.

Impero
Impero is the move that allows one player to utilize his opponents Units. This is signaled by stacking an owned Unit on top of a foreign one.


 * Only two Units may be stacked together
 * Units above the height of 5 may not be on top of an Impero Unit
 * The Impero-Condition must be met: For every 2 pieces below there must be 1 piece on top!

Impero-Units may only emerge during an Attack.

Moving
All former rules apply, but the pattern for the movement can now be chosen:


 * Moving like the captured Unit: all pieces move together.
 * Moving like the own / controlling Unit: only the own pieces are moved (again all of them).

Attacking
All former rules apply, but if an Impero-Unit participates the pattern for the attack must be chosen. Regardless to which pattern is chosen, the amount of pieces taken depends on the Unit whose pattern is being used. Their strength does not add up.

If the target hexagon is empty, the Impero-Unit may replace the former Unit. The rules for moving an Impero-Unit, depending on the chosen pattern must be considered.

If an Impero-Unit is attacked and cannot meet the Impero-Condition any more, all pieces must be taken off the board, liberating the captured Unit. In this case the target hexagon is not empty, even though all enemy pieces were taken. Thus no Unit may be moved on the target hexagon.

Decombination / Disassembly
All former rules apply, but if an Impero-Unit is chosen, then either enough pieces are left on the original hexagon to still meet the Impero-Condition or all pieces are distributed, liberating the opponents Unit. The Unit still has to be distributed over at least 2 hexagons.

Combination / Merging
All former rules apply, if an Impero-Unit donates, then either enough pieces are left to still meet the Impero-Condition or all pieces are donated, liberating the opponents Unit. One cannot rearrange the opponents pieces or carry them on.

Symmetrical Combination / Merging
All former rules apply, the Units must still be exactly the same and donate exactly the same.

Win
A game can be won in the following ways:
 * Nex: The opposing Tribun was taken off the board
 * Paralysis: The opponent has no legal move (very rare as sacrificing the Tribun is legal)
 * Resignation: A player may resign, conceding the game to the opponent.
 * Win on time: In games with a time control, a player wins if the opponent runs out of time, even if the opponent has a superior position.
 * Forfeit: A player who cheats, violates the rules, or violates the rules of conduct specified for the particular tournament can be forfeited. Occasionally, both players are forfeited.

Draw
There are 2 ways a game can end in a draw:
 * Draw by agreement: Draws are most commonly reached by mutual agreement between the players.
 * Draw on time: In games with a time control, the game is drawn if a player is out of time and no sequence of legal moves would allow the opponent to checkmate the player.
 * Draw by intervention: In tournament Tribun a game can be forcefully cancelled should neither player agree to a draw and the length of the game interferes with the schedule or take too much of a toll on the players.

Nex
The player whose Tribun is taken off the board first looses. Because the Tribun must be the highest piece in every Unit he will always be taken first. Thus the height of the Tribun-Unit does not provide cover for the Tribun. One is not obligated to defend the Tribun and neither to take the opponent when the opportunity presents itself.

Should a Tribun be attacked then these are the optimal (not loosing) responses:


 * The threat can be taken off the board or impero.
 * The threat can be harmed such that the resulting Unit cannot still take the Tribun.
 * If the Unit is blockable (4, 6, 8) the attack might be able to be interposed by means of moving or decombining a Unit.

These responses might fail in case of a double attack. Because only one Unit at a time can be dealt with, attacking with 2 or more Units simultaneously is a very strong threat. This usually happens by splitting a big Unit into many smaller Units. These responses might also work against a double attack:


 * The Tribun can be moved away
 * The Tribun can be combined away

If these are also not a viable escape strategies then there is no escape.

Time control
In competition, Tribun games are played with a time control. If a player's time runs out before the game is completed, the game is automatically lost. The duration of a game ranges from ours to minutes.