Tonight we'll be writing programs to play tic-tac-toe!

If regular tic-tac-toe turns out to be too easy, try the "ultimate" version instead: http://mathwithbaddrawings.com/2013/06/16/ultimate-tic-tac-toe/

We may have our programs play against each other, so keep that in mind when designing your interface. (You can hard code it, but have a function that takes a board and returns a new board, and an easy way to access that.)