Provided by: atom4_4.1-5.1_amd64 bug

NAME

       atom4 - two-player color puzzle game

SYNOPSIS

       atom4 [ -a n ] [ -d level ] [ -mt | -mx ]
       atom4 -h

DESCRIPTION

       Atom-4  is  a two-player color manipulation game played with colored spherical pieces on a
       board divided into equilateral triangles. The player who first makes a row of 4 pieces  of
       the right color wins.

       There  is  an  AI  mode  where  you  play  against the computer. By default, atom4 runs in
       2-player mode. Since 2-player mode is controlled from the same terminal, it can be used as
       a  "practice" mode to acquiant oneself with the color change rules or to explore strategic
       possibilities in a controlled way.

       atom4 supports both a curses-based text interface and an X11 interface. The interface  can
       be  selected  with  the  -m  option.  By  default, atom4 launches the X11 interface if the
       $DISPLAY environment variable is set, and the curses-based interface otherwise.

OPTIONS

       -a n   Play against AI player.  n must be either 1 or 2, specifying which  player  the  AI
              will be.

       -d n   Set  AI  player's  difficulty  level,  where  n is an integer from 0 or larger. The
              default difficulty setting is 2.  This  version  of  Atom-4  uses  a  real  min-max
              algorithm;  higher  difficulty  settings  are  actually  much  harder unlike in the
              previous version. However, be warned that very high difficulty settings will likely
              be very slow, as the game tree grows very quickly.

       -h     Shows a summary of command-line options that atom4 takes.

       -mt    Selects  the  text  (curses-based) interface. The curses-based interface requires a
              terminal with color capabilities; at least 9 colors are needed.

       -mx    Selects the X11 interface. The X11 interface requires an X display that supports at
              least  8-bit  color. Note that currently, atom4 will always connect to the X server
              specified in the $DISPLAY environment variable.

TEXT MODE INTERFACE

       The text mode interface requires a terminal that supports at least 9 colors.

       The game controls are straightforward: the keypad arrow keys move the  cursor  around  the
       board,  and the Enter key or the Space key will place the piece being played on the board.
       The panel on the right shows you which piece is currently being played. Gameplay  proceeds
       until one of the players win.

       You can press q at any time to quit the game.

       After  one  of  the players win, the game will pause. You can either press n to proceed to
       the next round, or q to quit.

X11 INTERFACE

       The X11 interface requires an X display which has at least 8-bit color.

       Gameplay on the X11 interface is simple: the color wheel in  the  right  panel  shows  the
       order  in  which  pieces are played, as well as the current player (number in the center).
       The current piece being played is highlighted in the  color  wheel.  To  play  the  piece,
       simply locate your mouse over the desired spot on the board and click the mouse button.

       When  it  is  your turn to play, and your mouse hovers over a legal position where you can
       place a piece, the piece you are currently playing will appear under the mouse cursor.  It
       is not actually placed on the board until you click the mouse button.

       At any time during the game, you may press q to quit the game.

       After one of the players win, press n to proceed to the next round.

GAME RULES

       (Adapted from the README file.)

       Pieces may be placed only on the vertices of the triangular game board divisions, and only
       if touching two other pieces which themselves are adjacent to each other  (i.e.,  it  must
       form   an   equilateral   triangle  with  two  adjacent  pieces  already  on  the  board).
       Theoretically, the board is unlimited in size; practically, we limit  it  to  16  vertices
       across and 16 rows down.

       Pieces have 8 different colors in total, grouped into 4 groups:

        - black
        - red, green, and blue (the primary, or "additive", colors)
        - yellow, cyan, and purple (the secondary, or "subtractive", colors)
        - white

       Black and white are also called "propagators" (explained below).

       The  first  player  plays  additive  colors, and must make a row of 4 whites. White is the
       "goal piece" of the first player.  Similarly, the second player plays subtractive  colors,
       and must make a row of 4 blacks. Black is the "goal piece" of the second player.

       Since  neither player can play their goal pieces directly, they need to combine the colors
       they play in order to form their goal pieces on the game board,  indirectly.  Whenever  an
       additive  or  subtractive  piece  is  put  on  the  board,  it changes the color of pieces
       surrounding it. The color changes are illustrated by the following color wheel:

                             red   yellow
                                \ /
                        purple --*-- green
                                / \
                            blue   cyan

       1) If the neighbouring piece has an adjacent color on the wheel, it does not  change.  For
              example,  if  red  is placed next to yellow or purple, the yellow or purple remains
              the same.

       2) If the neighbouring piece has a color 60 degrees away on the wheel, then it changes  to
              the  color in between. For example, if red is placed next to green, the green turns
              into a yellow. If a red is placed next to a blue, the blue turns purple.

       3) If the neighbouring piece has the opposite color on  the  wheel,  then  it  changes  to
              either white or black, depending on what type of color the new piece is. If the new
              piece is an additive piece, the neighbour becomes white; if  it  is  a  subtractive
              piece, the neighbour becomes black. For example, if a red is placed next to a cyan,
              the cyan turns white; but if a cyan is placed next to the red, the red turns black.

       4) If the new piece is additive and the  neighbouring  piece  is  black,  then  the  black
              changes  to  the  same  color  as  the  new  piece.  Similarly, if the new piece is
              subtractive and the neighbouring piece is white, then the white changes to the same
              color as the new piece.

       5)  If  the new piece is additive and the neighbouring piece is white, then the white does
              not change, but the color change effect "propagates" through the white to the piece
              behind  the  white. That piece then changes as though the new piece had been placed
              next to it. If it is also white, then the effect continues propagating in the  same
              direction, in a straight line, until it reaches a non-white piece, and then changes
              that non-white piece as though the new piece was placed next to  it.  If  an  empty
              spot  is  reached  before  a non-white piece, then nothing happens. Because of this
              effect, white pieces are also called "additive propagators".

       6) Similarly, if the new piece is subtractive and the neighbouring  piece  is  black,  the
              color  change  effect  propagates  in the direction of the black until it reaches a
              non-black piece, which then changes as though the new piece had been placed next to
              it.  Nothing  happens  if an empty spot is reached before a non-black piece. Hence,
              black pieces are also called "subtractive propagators".

       (Another way to understand the color changes is treat  colors  as  red,  green,  and  blue
       combinations.  Additive  colors  always try to "add" themselves to their neighbours: red +
       green = yellow (red & green together); red + cyan (green  &  blue)  =  white.  Subtractive
       colors  try  to  remove  their  complement  color  from their neighbours. For example, the
       complement of yellow (red & green) is blue; so  yellow  tries  to  remove  blue  from  its
       neighbours.  Hence,  when  yellow (red & green) is placed next to cyan (green & blue), the
       cyan turns green (loses the blue component). Similarly, when cyan (green & blue) is placed
       next to white (red & green & blue), it removes its complement, red, from the white; so the
       white becomes cyan as well. In other words, additive colors  behave  like  colored  light,
       whilst subtractive colors behave like colored paint.)

       The  initial state of the board consists of two pieces, green and purple, in the middle of
       the board, touching each other. The first player then plays a red, the second player plays
       a  yellow,  and  then  the  first  player  plays  a  green, and so on, taking turns, going
       clockwise around the color wheel. The first person to make a row of 4 propagators wins.

       If the game is played in multiple rounds, the second player may start first on the  second
       round,  using a subtractive piece, and then the first player with the next color clockwise
       on the color wheel, and so on. The starting configuration always consists of  two  pieces,
       one  30 degrees counterclockwise from the starting color on the color wheel, and the other
       60 degrees clockwise; each touching the other in the center of the board.

GAME STRATEGY CONSIDERATIONS

       Notice that in order to get from additive colors to white,  the  first  player  must  form
       secondary  colors  and  then  add  their  complements; but the second player already plays
       secondary colors. So the first player can make use of the  pieces  played  by  the  second
       player  to  make whites, which is faster than building whites from scratch. Similarly, the
       second player plays subtractive pieces and must first form primary colors and then add the
       complements to make black; but the first player already plays primary colors, which can be
       exploited to make blacks.

       This also means that when playing a piece, one should be careful  not  to  give  too  much
       advantage to the other player by providing material to make propagators (black or white).

       Propagators  (blacks  or  whites) are useful for changing colors of pieces already blocked
       from direct access because they are surrounded by other pieces. Using propagators, you can
       create  more  propagators  from such "buried" pieces. Strategic positioning of propagators
       that allow you to reach these "internal" pieces is key to winning the game.

       Since it is relatively easy for one's opponent to prevent one from winning by changing the
       color  of a piece intended to be the 4th propagator in the row of 4, a good strategy is to
       devise a way to have at least two different pieces that can serve as a 4th  piece  in  the
       row.  Another  good strategy is to bury the prospective 4th piece with other non-essential
       pieces so that the opponent cannot easily reach it, and have multiple propagator paths  to
       it.   Then  if  the opponent blocks one propagator path, another one is available to reach
       it.

       It is very useful to anticipate the color of one's subsequent piece, and plan accordingly.
       For  example,  if  the first player is playing a red, and there are no cyans around, it is
       useful to place the red next to blue  pieces,  because  they  form  purple  which  can  be
       complemented  by  the green on the next turn. If they are placed next to green pieces, the
       result is yellow, which cannot be used until 2 turns later.

HISTORY

       The original 2-color version of the game was developed in December 2002. It was  based  on
       much  simpler rules (basically, each player directly plays his goal piece), but because of
       the very small initial state space and the proximity of winning states, one player  always
       had  the  advantage.  Several  different  starting  configurations,  including  randomized
       starting states, were tried in an attempt to balance the game, but with limited results.

       Because of these limitations, more elaborate  versions  of  the  game  were  sought.   The
       current  8-color version was first introduced in February 2003. Its main motivation was to
       postpone winning states until the state space has grown significantly.

       A min-max algorithm with alpha/beta pruning was introduced to the AI player in April 2003.
       This  replaced  the  previous, more limited algorithm which only performed well at certain
       search depths.

       The "4" in the name "Atom-4" refers obviously to the goal of making  the  4-in-a-row.  The
       "atom"  part  refers  to the similarity to atoms forming into a crystal lattice: you can't
       just stick an atom anywhere in a crystal lattice; it must fit into a "stable" position (in
       this  case,  touching  two other adjacent "atoms" already on the board). Also, atoms don't
       just stick together; chemical reactions (color changes) happen when  they  come  together,
       and  some chemical changes have far-reaching effects (color change propagating over whites
       and blacks).

AUTHOR

       The game concept of Atom-4, the design and implementation of the software version  of  the
       game,   and   the   graphics  used  by  the  game,  were  all  done  by  Hwei  Sheng  Teoh
       <hsteoh@debian.org>.

COPYRIGHT

       Copyright (C) 2002-2003 by Hwei Sheng Teoh <hsteoh@debian.org>

       This is free software; you can redistribute it and/or modify it under the terms of the GNU
       General  Public License as published by the Free Software Foundation; either version 2, or
       (at your option) any later version without ANY WARRANTIES.

                                                                                         ATOM4(6)