
1.        Introduction:

1.1.      SPACESHIPS is a zero-sum game for two players, which can be played
          either as a single game[2] or a series of games making up a
          match[7].

1.2.      It is played in two SPACEs, one for each player.
1.2.1.    Each space is a 3-dimensional 5x5x5 grid of cubical CELLs of which
1.2.2.    only the identity and relationship between the cells (not the size,
          exact shape, orientation or handedness) is relevant.
1.2.3.    Cells are ADJACENT if they share faces; sharing edges is not
          sufficient.
1.2.4.    The spaces do not `wrap'.

1.3.      The object of the game is to cause all of your opponent's ships[3]
          to be destroyed[3.6] before they destroy yours.

1.4.      Spaceships is not a game of perfect information.  Players record
          their play privately, revealing only certain information to each
          other, and
1.4.1.    reveal their records of their play for checking by the other player
          after each game[2] is finished.
1.4.2.    Mutually trusting players need not reveal their records of the game
          to each other.

2.        A GAME consists of the following phases:

2.1.      SETUP: each player secretly records the locations of their ships[3].

2.2.      Thereafter play proceeds in TURNs.  During each turn
2.2.1.    the two players first secretly record their actions[4] for that turn
          and the effects of those actions; when both players have done so
2.2.2.    each reveals the VISIBLE ASPECTs of these actions to the other.
2.2.3.    Finally, each player records secretly the effects of these visible
          aspects, and makes known their VISIBLE RESULTs.
2.2.4.    The availability of actions, and their effects and visible aspects,
          and the possible effects and visible results are defined below,
          along with the actions[4].

2.3.      Termination:
2.3.1.    If at the end of a turn[2.2] either player has no ships[3] which are
          not destroyed[3.6] the game terminates[2.3.3] immediately.
2.3.2.    If at the start of a turn[2.2] either player has no possible
          actions[4] other than kamikaze strikes[4.4], and during that turn
          the player does not record any actions, then the game
          terminates[2.3.3] at the end of the turn.
2.3.3.    When the game TERMINATES the player who has the most remaining
          materiel[2.3.4] is the winner; if both players have the same amount
          then the game is a draw.
2.3.4.    A player's REMAINING MATERIEL is the number of undamaged[3.4] cells
          in their ships[3] at the end of the game.

2.4.      References to the state of a cell refer to the state at the start of
          the turn[2.2], unless otherwise specified.

3.        A SHIP is a tuple consisting of a type[6] and a subset of the cells
          in a player's space recorded as such by that player in the
          setup[2.1] phase of the game.

3.1.      Each ship's subset of the space must conform to the requirements for
          its type.

3.2.      Each player must record exactly as many ships of each type as are in
          that player's fleet[3.3].

3.3.      Each player's FLEET consists of one ship each of the following
          types: death star[6.1], kill cruiser[6.2], flying saucer[6.3],
          missile destroyer[6.4] and heavy fighter[6.5], plus any additional
          ships due to to the rules for matches[7].

3.4.      After setup[2.1] each cell belonging to a ship is either UNDAMAGED
          or DESTROYED.  Every such cell is undamaged immediately after setup;
          it may become destroyed during the game.

3.5.      A ship is DAMAGED if some but not all of its cells are
          destroyed[3.6].

3.6.      A ship is DESTROYED when all of its cells are destroyed[3.6].

3.7.      No two ships (belonging to the same player) may intersect.

4.        ACTIONs:

4.1.      For each action, the player taking the action is called the ACTIVE
          PLAYER; the other player is called the PASSIVE PLAYER.  Note that in
          each turn each player is both the active player (for their own
          actions) and the passive player (for their opponent's).

4.2.      Each player may make in a turn[2.2] any or all of the following
          actions when and insofar as they are permitted.  The information to
          be recorded for each action and its effects and visible
          aspects[2.2.2] are specified with each action in the list below:

4.3.      CONVENTIONAL STRIKEs:
4.3.1.    Unless otherwise stated, a single conventional strike may be
          launched per turn[2.2] for every distinct adjacent[1.2.3] pair of
          undamaged[3.4] cells belonging to the same ship[3].
4.3.2.    A conventional strike must be recorded as such together with the
          coordinates[8.1] of the single target[5.1.1] cell.
4.3.3.    A conventional strike has no effects on the active player[4.1].
4.3.4.    The visible aspect[2.2.2] of a conventional strike is a strike[5.1]
          on the target cell.

4.4.      For each ship[3] which does not entitle its player to a conventional
          strike[4.3] in a turn[2.2] the player may instead launch one
          KAMIKAZE STRIKE in that turn:
4.4.1.    A kamikaze strike must be recorded as such together with the
          coordinates[8.1] of the KAMIKAZE LAUNCH and target[5.1.1] cells.
4.4.2.    The kamikaze launch cell must be an undamaged[3.4] cell in the ship.
4.4.3.    Effect: the kamikaze launch cell becomes destroyed[3.6] at the end
          of the turn[2.2].
4.4.4.    The visible aspect[2.2.2] of a kamikaze strike is a strike[5.1] on
          the target[5.1.1] cell and the kamikaze death[5.3] of the kamikaze
          launch cell.

4.5.      A ship[3] may entitle its player to additional actions.

4.6.      The active player[4.1] need not record which strikes[5.1] were
          enabled by which ships[3] and rules.

5.        The visible aspect[2.2.2] of an action[4] may be one of the
          following.  The information to be passed to the passive player[4.1],
          the visible aspect's possible effects on the passive player and the
          corresponding visible results[2.2.3] are specified with each
          possible visible aspect in the list below:

5.1.      STRIKEs:
5.1.1.    A strike is identified as such and by the TARGET cell in the passive
          player's space.
5.1.2.    If the target cell does not belong to a ship[3] there is no effect
          on the passive player and the visible result is a MISS.
5.1.3.    If the target cell belongs to a ship and is undamaged[3.4] then the
          cell becomes destroyed[3.6] at the end of the turn[2.2] and the
          visible result is a HIT.
5.1.4.    If the target cell belongs to a ship and is destroyed[3.6] then
          there is no effect on the passive player[4.1] and the visible result
          is a DUPLICATE HIT.
5.1.5.    Other rules may specifiy additional effects and visible results for
          a strike.

5.2.      A BEAM STRIKE (the visible aspect of a beam weapon[6.1.3]) has the
          same visible aspect, effects on the passive player and visible
          results as a strike[5.1], except that its visible aspect identifies
          it as beam strike rather than a strike.

5.3.      A KAMIKAZE DEATH
5.3.1.    is identified as such and by the kamikaze launch[4.4.1] cell in the
          active player's[4.1] space.
5.3.2.    A kamikaze death has no effect on the passive player and
5.3.3.    no visible results.

6.        TYPEs of ships[3]

6.1.      DEATH STAR:
6.1.1.    A death star contains eight adjacent[1.2.3] cells in a 2x2x2 cube.
6.1.2.    Each death star entitles its player to only one conventional
          strike[4.3] per turn[2.2], but it does so until it is
          destroyed[3.6].
6.1.3.    Each undamaged[3.4] death star entitles its player to one use of a
          BEAM WEAPON as an action[4] during that turn.
6.1.3.1.  The visible effect of the beam weapon is a set of beam strikes[5.2]
          in a set of target[5.1.1] cells.
6.1.3.2.  The target cells are a set of 5 adjacent[1.2.3] cells lying in a
          straight line.
6.1.3.3.  The cells in the active player's[4.1] space corresponding to the
          target[5.1.1] cells in the passive player's[4.1] space must
          intersect the death star.

6.2.      A KILL CRUISER contains six adjacent[1.2.3] cells in a 3x2x1
          rectangle.

6.3.      A FLYING SAUCER contains four adjacent[1.2.3] cells in a 2x2x1
          square.

6.4.      MISSILE DESTROYER
6.4.1.    A missile destroyer contains three adjacent[1.2.3] cells lying in a
          straight line.
6.4.2.    Each undamaged[3.4] cell in a missile destroyer is a missile[6.6].

6.5.      A HEAVY FIGHTER contains two adjacent[1.2.3] cells.

6.6.      A MISSILE is either an UNFIRED MISSILE or a FIRED MISSILE.
6.6.1.    After setup[2.1] each missile starts as an unfired missile; it may
          become a fired missile or be destroyed[3.6] during the game.
6.6.2.    Each ship[3] which contains an unfired missile entitles its player
          to one MISSILE STRIKE as an additional action[4] in that turn.
6.6.2.1.  A missile strike must be recorded as such together with the identity
          of the MISSILE LAUNCH cell (which must be an unfired missile in the
          ship which enables the missile strike) and the target[5.1.1] cell.
6.6.2.2.  The effect of a missile strike (on the active player[4.1]) is to
          cause the missile launch cell to become a fired missile just before
          the visible aspects[2.2.2] are revealed.
6.6.2.3.  The visible aspect of a missile strike is a strike[5.1] on the
          target[5.1.1] cell.
6.6.3.    A strike[5.1] whose target[5.1.1] cell is still an unfired missile
          just after visible aspects are revealed additionally:
6.6.3.1.  has the effect on the passive player[4.1] of causing any
          adjacent[1.2.3] undamaged[3.4] cells in the same ship[3] to become
          destroyed[3.6] at the end of the turn[2.2] and
6.6.3.2.  has as visible result MISSILE EXPLOSIONs in the target[5.1.1] cell
          and any adjacent undamaged cells in the same ship.

7.        MATCHes:

7.1.      A pair of players may agree to play several games[2] as a single
          match.

7.2.      In every game[2] except the first each player's fleet[3.3] contains
          additional ships[3] containing as many cells as they had remaining
          materiel[2.3.4] in the previous game[2].

8.        Notation:

8.1.      Conventionally, the cells[1.2.1] are identified by their three
          cartesian COORDINATES.  The three coordinates and their values and
          orderings are:
8.1.1.    colour: Red, Orange, Yellow, Green, Blue, abbreviated R O Y G B.
8.1.2.    letter: v, w, x, y, z.
8.1.3.    number: 1, 2, 3, 4, 5.
8.1.4.    The conventional order for writing down and reading out coordinates
          is colour, letter, number.  Coordinates are usually written as
          triples of characters without spaces.
8.1.5.    Case is significant in the notation - it is required for
          distinguishing Y (Yellow) from y.

8.2.      Actions are conventionally recorded as follows:
8.2.1.    A conventional strike[4.3] is recorded as the triple for the
          coordinates of the target[5.1.1] cell.
8.2.2.    The use of a beam weapon[6.1.3] is recorded as b followed by the two
          coordinates which together identify the line of target cells.
8.2.3.    A missile strike[6.6.2] is recorded as m followed by sufficient
          coordinate value(s) to uniquely identify the missile launch[6.6.2.1]
          cell, and as one additional strike target cell.
8.2.4.    A kamikaze strike[4.4] is recorded as k followed by the coordinates
          of the kamikaze launch[4.4.1] cell, and as one additional strike
          target cell.
