["", "", ""],

  ["", "", ""],

  ["", "", ""],

];

​

let players = ["X", "O"];

​

let currentPlayer;

let available = [];

​

function setup() {

  createCanvas(400, 400);

  frameRate(1);

  currentPlayer = floor(random(players.length));

  for (let j = 0; j < 3; j++) {

    for (let i = 0; i < 3; i++) {

      available.push([i, j]);

    }

  }

}

​

function equals3(a, b, c) {

  return a == b && b == c && a != "";

}

​

function checkWinner() {

  let winner = null;

​

  //horzontal

  for (let i = 0; i < 3; i++) {

    if (equals3(board[i][0], board[i][1], board[i][2])) {

      winner = board[i][0];

    }

  }

  //vertical

  for (let i = 0; i < 3; i++) {

    if (equals3(board[0][i], board[1][i], board[2][i])) {

      winner = board[0][i];

    }

  }

  //diagonal

  if (equals3(board[0][0], board[1][1], board[2][2])) {

    winner = board[0][0];

  }

  if (equals3(board[2][0], board[1][1], board[0][2])) {

    winner = board[2][0];

  }

​

  if (winner == null && available.length == 0) {

    return "tie";

  } else {

    return winner;

  }

}

​

function nextTurn() {

  let index = floor(random(available.length));

  let spot = available.splice(index, 1)[0];

  let i = spot[0];

  let j = spot[1];

  board[i][j] = players[currentPlayer];

  currentPlayer = (currentPlayer + 1) % players.length;

}

​

function draw() {

  background(255);

  let w = width / 3;

  let h = height / 3;

​

  line(w, 0, w, height);

  line(w * 2, 0, w * 2, height);

  line(0, h, width, h);

  line(0, h * 2, width, h * 2);

​

  for (let j = 0; j < 3; j++) {

    for (let i = 0; i < 3; i++) {

      let x = w * i + w / 2;

      let y = h * j + h / 2;

      let spot = board[i][j];

      textSize(32);

      strokeWeight(4);

      if (spot == players[1]) {

        noFill();

        ellipse(x, y, w / 2);

      } else if (spot == players[0]) {

        let xr = w / 4;

        line(x - xr, y - xr, x + xr, y + xr);

        line(x + xr, y - xr, x - xr, y + xr);

      }

    }

  }

​

  let result = checkWinner();

  if (result != null) {

    noLoop();

    createP(result).style("color", "#FFF").style("font-size", "32pt");

  } else {

    nextTurn();

  }

}

​