function winner(board)

{

    for (var i=0; i<3; ++i) {

        if (board.children[i].state!=""

            && board.children[i].state==board.children[i+3].state

            && board.children[i].state==board.children[i+6].state)

            return true

        if (board.children[i*3].state!=""

            && board.children[i*3].state==board.children[i*3+1].state

            && board.children[i*3].state==board.children[i*3+2].state)

            return true

    }

    if (board.children[0].state!=""

        && board.children[0].state==board.children[4].state!=""

        && board.children[0].state==board.children[8].state!="")

        return true

    if (board.children[2].state!=""

        && board.children[2].state==board.children[4].state!=""

        && board.children[2].state==board.children[6].state!="")

        return true

    return false

}

function restart()

{

    // No moves left - start again

    for (var i=0; i<9; ++i)

        board.children[i].state = ""

}

function makeMove(pos,player)

{

    board.children[pos].state = player

    if (winner(board)) {

        win(player + " wins")

        return true

    } else {

        return false

    }

}

function computerTurn()

{

    var r = Math.random();

    if(r < game.difficulty){

        smartAI();

    }else{

        randAI();

    }

}

function smartAI()

{

    function boardCopy(a){

        var ret = new Object;

        ret.children = new Array(9);

        for(var i = 0; i<9; i++){

            ret.children[i] = new Object;

            ret.children[i].state = a.children[i].state;

        }

        return ret;

    }

    for(var i=0; i<9; i++){

        var simpleBoard = boardCopy(board);

        if (board.children[i].state == "") {

            simpleBoard.children[i].state = "O";

            if(winner(simpleBoard)){

                makeMove(i,"O")

                return

            }

        }

    }

    for(var i=0; i<9; i++){

        var simpleBoard = boardCopy(board);

        if (board.children[i].state == "") {

            simpleBoard.children[i].state = "X";

            if(winner(simpleBoard)){

                makeMove(i,"O")

                return

            }

        }

    }

    function thwart(a,b,c){//If they are at a, try b or c

        if (board.children[a].state == "X") {

            if (board.children[b].state == "") {

                makeMove(b,"O")

                return true

            }else if (board.children[c].state == "") {

                makeMove(c,"O")

                return true

            }

        }

        return false;

    }

    if(thwart(4,0,2)) return;

    if(thwart(0,4,3)) return;

    if(thwart(2,4,1)) return;

    if(thwart(6,4,7)) return;

    if(thwart(8,4,5)) return;

    if(thwart(1,4,2)) return;

    if(thwart(3,4,0)) return;

    if(thwart(5,4,8)) return;

    if(thwart(7,4,6)) return;

    for(var i =0; i<9; i++){//Backup

        if (board.children[i].state == "") {

            makeMove(i,"O")

            return

        }

    }

    restart();

}

function randAI()

{

    var open = 0;

    for (var i=0; i<9; ++i)

        if (board.children[i].state == "") {

            open += 1;

        }

    if(open == 0){

        restart();

        return;

    }

    var openA = new Array(open);//JS doesn't have lists I can append to (i think)

    var acc = 0;

    for (var i=0; i<9; ++i)

        if (board.children[i].state == "") {

            openA[acc] = i;

            acc += 1;

        }

    var choice = openA[Math.floor(Math.random() * open)];

    makeMove(choice, "O");

}

function win(s)

{

    msg.text = s

    msg.opacity = 1

    endtimer.running = true

}