[Android]
Access the Android Market and search for Crystal Defenders.

[iPod/iPhone]
Access the App Store and search for Crystal Defenders.

[PlayStation 3]
Access the PlayStation Network to purchase the game.

[Wii Ware]
Access the Wii Shop Channel to purchase the game.

[Xbox LIVE]
You can purchase the game from XBOX LIVE's Games on Demand or through the XBOX LIVE Marketplace on the Web.

XBOX LIVE Marketplace:
http://marketplace.xbox.com/en-US/default.htm