The full game.
Build&Defend requires Java in order to work. If Java is not installed on your computer, you can download it at www.java.com.
If you want to configure your router to host online public games, we invite you to read the F.A.Q..
Follow the Java 64 Bits guide if you are using Java 32 and the game runs out of memory.
See the command launch page for advances usages.