diff --git a/react-fb-tictactoe/src/TicTacToe/index.js b/react-fb-tictactoe/src/TicTacToe/index.js
index 56944d57..06b10441 100644
--- a/react-fb-tictactoe/src/TicTacToe/index.js
+++ b/react-fb-tictactoe/src/TicTacToe/index.js
@@ -1,7 +1,6 @@
 import React, { Component } from 'react';
 import './TicTacToe.css'
 
-
 /*
  * Changes from original tutorial
  *  - Here we import Component, so we can replace
@@ -9,23 +8,55 @@ import './TicTacToe.css'
  *    with
  *    class Square extends Component
  */
-class Square extends Component {
-  render() {
-    return (
-      <button className="square">
-        {/* TODO */}
-      </button>
-    );
-  }
+
+/* The Square component renders a single <button> */
+function Square(props) {
+  return (
+    <button className="square" onClick={props.onClick}>
+      {props.value}
+    </button>
+  );
 }
 
+/* The Board component renders 9 squares */
 class Board extends Component {
+  constructor() {
+    super();
+    this.state = {
+      squares: Array(9).fill(null),
+      xIsNext: true,
+    };
+  }
+
+  handleClick(i) {
+    const squares = this.state.squares.slice();
+    if (calculateWinner(squares) || squares[i]) {
+      return;
+    }
+    squares[i] = this.state.xIsNext ? 'X' : 'O';
+    this.setState({
+      squares: squares,
+      xIsNext: !this.state.xIsNext,
+    });
+  }
+
   renderSquare(i) {
-    return <Square />;
+    return (
+      <Square 
+        value={this.state.squares[i]} 
+        onClick={() => this.handleClick(i)} 
+      />
+    );
   }
 
   render() {
-    const status = 'Next player: X';
+    const winner = calculateWinner(this.state.squares);
+    let status;
+    if (winner) {
+      status = 'Winner: ' + winner;
+    } else {
+      status = 'Next player: ' + (this.state.xIsNext ? 'X' : 'O');
+    }
 
     return (
       <div>
@@ -50,6 +81,7 @@ class Board extends Component {
   }
 }
 
+/* The Game component renders a board with some placeholders */
 class Game extends Component {
   render() {
     return (
@@ -67,3 +99,23 @@ class Game extends Component {
 }
 
 export default Game;
+
+function calculateWinner(squares) {
+  const lines = [
+    [0, 1, 2],
+    [3, 4, 5],
+    [6, 7, 8],
+    [0, 3, 6],
+    [1, 4, 7],
+    [2, 5, 8],
+    [0, 4, 8],
+    [2, 4, 6],
+  ];
+  for (let i = 0; i < lines.length; i++) {
+    const [a, b, c] = lines[i];
+    if (squares[a] && squares[a] === squares[b] && squares[a] === squares[c]) {
+      return squares[a];
+    }
+  }
+  return null;
+}