Hello, Android, 4th Edition

Creating the Tic-Tac-Toe Example

Everybody knows how to play Tic-Tac-Toe: a 3×3 array of tiles, initially empty, is filled in by two players who mark either an X or an O in an empty spot. The first player to get three of their marks in a row wins. If the board fills up first, then that’s a tie and nobody wins.

Ultimate Tic-Tac-Toe^[28] is similar, except that you can’t simply put a mark in your square—you have to win the square by playing a nested game of Tic-Tac-Toe using a 3×3 array of smaller tiles inside the big one. See the figure for an example.

Figure 2. Tic-Tac-Toe meets Inception

There are many variations, but we’re going to use the one ...