The download button opens the iTunes App Store, where you
may continue the download process. You must have iTunes installed with an
active iTunes account in order to download and install the software. This
download may not be available in some countries.
From Curious Bit:
How high can you fly using our original twitchy control system?Beat your own high score or compete online with your friends.Master the controls and enjoy the flow![Bird controls]- tap to change direction- hold for extra speed[Tip]- use extra speed to navigate a large stretch between two pipe openings!