Castlewars is a card game in which players from both sides can win by being the first to build a hundred storey castle or destroy the opponent's castle entirely. A number of cards are shown at the bottom of the screen, and the player has to decide which card to play for each turn by clicking on it. Cards can be discarded from their hands by holding down the control key while selecting a card. Only one card can be discarded during each turn.

This is a remake of the classic game Ants.