

o Black or brown
o Horizontal or vertical o Solid or hollow o Round or square  
This makes a total of 16 possible pieces and there are exactly one piece of each type (so each piece can be represented by a binary number of length 4).
Initially, the board is empty and it is successively filled with pieces. The game is over when a row, a column or a diagonal has four pieces carrying a common property in it, e.g. four black pieces. The player who places the fatal piece loses.
The game is a twoplayer game, although in the current release, only the humancomputer combination is supported. Player 1 (the human by default) chooses one of the 16 pieces. Player 2 (the computer by default) places this piece on one of the 16 squares of the board and chooses a piece out of the remaining 15 pieces which he gives to player 1, who places this piece on one of the remaining 15 squares on the board, etc.
As mentioned above, the game is over when a player places a piece in such a way that a row, a column or a diagonal (but see below) contains four pieces carrying a common property. The player who places this piece loses. If there is no empty square left, we have a draw (yes, this can happen).
There are two menus, the Actions Menu and the Options Menu.
New game  You start Starts a new game of xtic, ending the previous one abruptly and letting the human start. New game  I start Identical to "New game  You start" except that the computer will begin the next game. Quit Exist from xtic.
Level trivial The easiest level. The computer only tries to place the selected piece in a way that it does not lose immediately, and chooses any free piece to give away, i.e. it thinks only one move ahead. Level easy The computer thinks two moves ahead. Level medium The computer thinks three moves ahead. Level hard The computer thinks four moves ahead. Level very hard The computer thinks five moves ahead. Level don’t try The computer thinks six moves ahead. This can be quite slow (and hard). Game Type: normal In addition to the rows and columns, the two main diagonals are dangerous (can make the game end). Game Type: nodiags Only the rows and columns are dangerous. Game Type: torus All 8 "diagonals" are dangerous. This corresponds to playing on a torus.
Probably plenty. Report any you find to mjo@math.kth.se
Mattias Jonsson, Dept of Mathematics, Royal Institute of Technology, S100 44 Stockholm, Sweden.email: mjo@math.kth.se, URL: http://www.math.kth.se/~mjo
Mattias Jonsson, KTH  XTIC (1)  X11 
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