It is a clone of the old arcade game Rampart. Up to four players (or more in future versions) build castle walls, place cannons inside these walls, and shoot at the walls of their enemy(s). If a player cannot build a complete wall around one of his castles, he loses. The last surviving player wins.
What's new in Castle-Combat
Simple single-player mode
Conquer mode is back
Fullscreen and Sound can be turned on/off
As always: a lot of small improvements, fixes and clean-ups