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 Pierre Schippert:
Be part of the Game!Design your own world. The best ones will be added to the game monthly and everyone can play them! Enter the game. Your mouse is already waiting! Before uploading your own world, check out the levels to learn more about the gameplay. Have fun collecting the cheese!