Tic Tac Toe Kata

This was a fun experiment on modeling a tiny game. The implementation is very basic; there are no players. But it should resemble the structure of all the basic components of the game.

Grid

The grid only knows about squares and marks. It doesn't enforce any rules. Only that it cannot have a mark outside its size; and it won't place a mark on a filled square. The grid is also immutable.

Game

The Game enforces the rules of tic-tac-toe. It also keeps track of which square has the turn. It only has a single public command; placeMark(int $square) which places the square on the grid.

GameEventListener

The Game receives a GameEventListener on which it calls all the possible events.

Mark

A mark is a simple enum of either X or O.

Rendering

For rendering, I opted for a CLI implementation. The CliUserInterface implements the GameEventListener and will render the Grid for visualization.

Usage

Run php index.php for a simple 3x3 game.
Run php index.php 4 to make it a little more challenging.
Run php index.php 1 or php index.php 2 to always win with X.