Castlevania: Circle of the Moon is the first of the series to be based on the action/RPG structure of Castlevania:Symphony of the Night rather than the level-based action style of all previous Castlevania games. Dracula's castle is a single continuous building, and as Nathan discovers artifacts within it he gains new abilities that allow him to explore more of it. While Nathan can only use his Killer Whip as a weapon, he can find and equip different kinds of armor and accessories that change his stats. Unique to this entry in the series is the Dual Set-up System, where a combination of two cards will give Nathan unique magical abilities. For example, equipping a fire type card with a whip card will give the Killer Whip a fire attribute, while equipping it with a summon card will let Nathan summon a fire demon to attack onscreen enemies.