Defend your castle against sticks, tanks, wizards and all sorts of demonic forces with plenty of spells, upgrades and weapons to help keep your castle standing.
Build up your castle by upgrading walls, and adding gunners, towers, archers. Use spells and runes to defend it.
The real-time strategy genre as we know it today--gathering resources, building bases, and massing huge armies to sweep your opponent from the map--owes a lot to Command & Conquer. The original Command & Conquer was one of the first true real-time strategy games, as well as one of the best games ever made.