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 Apocolyp Software:
The country is under attack! As part of the Nuclear Defence Force it is your job to defence the 5 cities, and a theme park from a nuclear attack. The game contains an online scoreboard system that allows users to track the best scores, best players, and the most recent scores.