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One of the crucial pieces of information we're missing is which player's piece is inside each square. Thanks to the isUsed boolean, we know when a square has a piece in it, but we have no idea which piece it is. Keeping better track of which piece occupies which square is the first step to detecting a win condition.

isUsed isn't a very information-packed variable. By replacing it with an int, we can use it to store more valuable data.

In the Square script, replace this:

var isUsed:boolean;

with this:

var player:int;

In the logic check, change this:

if(!isUsed)

to this:

if(player == 0)

and remove this line from the OnMouseDown function:

isUsed = true;

Altogether, the Square script should look like this:

#pragma strict
var x:int;
var y:int;
var player:int;

var gameLogic:GameObject;

function Start () 
{
  gameLogic = GameObject.Find("GameLogic");
}

function OnMouseDown()
{
  if(player == 0)
  {
    gameLogic.GetComponent(GameLogic).ClickSquare(gameObject);
  }
}

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