The "Download Now" link directs you to the iTunes App Store, where you must continue the download process. You must have iTunes installed in order to open the link, and you must have an active iTunes account to download the application. This download may not be available in some countries.
Just like traditional Tic-Tac-Toe, try to get three in a row in any direction before your opponent. But beginning with your fourth move, your oldest move will DISAPPEAR with every new turn! Incredibly simple, yet amazingly challenging.