Try beating it and destroying all the enemies. That was the original goal in each level, but we figured only destroying the castles would make it easier for less skilled players.
Anyway... Me and Terry got a decent level editor done, as well as an awesome online database of user created content. All levels are uploaded and download directly from the game. Convenient eh?
Let's see some more levels!
PS. Huge levels won't be able to upload. Those have to be shared through the local copy of the level in your game folder (.xpl files).
Edit: Forgot to include a dll.
http://64digits.com/users/cactus/xoldiers.zip