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 Appocalyps UG (haftungsbeschraenkt):
Birds are boring, let's fly with a Monster! Tap the little cute Monster trough the wholes between the ballons. But be careful, as higher your score is, as harder it will be!