Tic-Tac-Toe Extensible Notation
T3EN is a notation system designed to represent the state of a Tic-Tac-Toe board for various board configurations, including standard and non-standard shapes.
It uses a combination of symbols to represent playable and non-playable cells, player moves, and the structure of the board, along with the side whose turn it is to play.
It is designed to balance readability, consistency, and efficiency.
_(underscore): Represents a playable cell..(dot): Represents a non-playable cell.x,o: Represent player moves (lowercase)./(slash): Used as a row delimiter.
T3EN employs variable-length encoding to efficiently encode consecutive cells
of the same type, which is common in tic-tac-toe. For example, 3_ represents
3 playable cells. The numeric prefix is only used when more than 1 cell of the
same type repeats, and only in the span of a single row.
The board state is followed by a space and the lowercase letter representing the player to move (x or o).
Bear in mind that T3EN is extensible therefore supports non-standard variants of tic-tac-toe with non-standard board shapes (other than typical square grids with all playable cells). However, the T3EN notation is expected to be used only to represent a square grid. This is to allow for deterministic behavior, while allowing incremental parsing.
3_/3_/3_ x - A standard 3x3 empty board with x to move. This is also the
starting position of a standard tic-tac-toe game.
_ _ _
_ _ _
_ _ _3_/_x_/3_ o - After x plays in the center from the previous empty board,
with o ready to play.
_ _ _
_ x _
_ _ _2_o/_x_/3_ x - After o plays in the top right on the previous board played
by x, with x set to play.
_ _ o
_ x _
_ _ _.3_./5_/.3_./5_/.3_. o - An hourglass shaped board, with some unplayable
cells, and o to move.
. _ _ _ .
_ _ _ _ _
. _ _ _ .
_ _ _ _ _
. _ _ _ .3_/3_ - A rectangular board (the number of rows and columns are different).
This can be represented, using a 3x3 grid with unplayable cells, for example:
3_/3_/3.
_ _ _
_ _ _
. . .3_/5_/3_ - An irregular board (the number of columns per row is uneven). This
can be represented using a 5x5 grid with unplayable cells, for example:
.3_./5_/.3_./5./5.
. _ _ _ .
_ _ _ _ _
. _ _ _ .
. . . . .
. . . . .This notation is inspired by the Forsyth-Edwards Notation, with special considerations applied to enable scaling to larger board sizes and simplified for tic-tac-toe.