4x4 5x5 6x6 Tic Tac Toe

A one person Tic Tac Toe game that you play against the phone/tablet, playing as "Bob." In 4x4 most people discover how to beat Bob, but it takes a while. 5x5 is harder yet, and 6x6 starts getting crazy. There is very little text, so it works in any language.