Tic-Tac-Toe for EasyToBook
==========================

A bit stupid tic-tac-toe game implemented in PHP 5+ for interaction in
a browser.

Requirements:
- Apache
- PHP 5+ (tested on 5.3.8)

Usage:
- Machine always makes the first move (plays with "X").
- Click an available radio button to mark an "O".
- The script will detect the following scenarios:
  - One of the players (machine or human) won.
  - The  game is stale (ie. no one wins).

Explanation:

It's a single file that contains the "model" (class model), the "view"
(class "view") and the "controller" (class "controller").

The script creates an instance of the "controller", and proceeds to dispatch
the request (action/method controller::play() is hardcoded as there are no
other routes). The action build in a "view" instance the response (HTML in this
case), and returns a string representation of it. The string is ultimately
echoed to STDOUT for display on the browser.

Machine's ticks are stored as -1, human's as 1, and not played yet cells as 0
values.

The "board" is stored as a 2-dimensional array. The "solutions" that mark a
winning position are a pre-calculated array.

In order to reduce memory consumption (not hat its much anyways), the
solutions are pre-computed in a "normalized" way, ticks are 1 and others are 0.
This means that after each move we loop through all solutions and check to see
if the human or the machine matched a winning position. To do this we convert
those -1, 1 to 1 by multiplying them by themselves (-1*-1=1, 1*1=1). Then the
solution is "mapped" into the board (ie. when values match keep them, else
dismiss them). If the mapping matches the solution then we know someone won.

The "stupid" part comes from the machine's playing strategy. Its very simple,
but guarantees it'll never lose:
- Machine always makes first move and plays with "X".
- On 1st move is always for the center of the grid.
- On 2nd move is for a free corner.
- On 3rd tries to close game by finishing diagonal.
- If diagonal not possible then force none wins by blocking human's actions.

Following these rules its not possible for the human to win, at most they can
obtain a stale.