Circle Of The Moon makes use of a 2D side-scrolling style of gameplay, similar to many of the previous Castlevania video games. The objective of Circle of the Moon is to lead player character Nathan Graves through a monster-filled castle as he searches for his kidnapped mentor. Like many of the previous Castlevania protagonists, Nathan uses a whip to attack and defeat enemies, alongside secondary weapons—an axe, cross, holy water, dagger and stopwatch—only one of which may be carried at any time by the player. Hearts, typically found within candles, determine the amount of any secondary weapon carried by him. Circle of the Moon follows a nonlinear style of gameplay: at the beginning of the game, Nathan can only traverse certain areas of the castle; by obtaining various abilities, such as becoming able to run, double jump, and wall kick, he gradually explores the castle. He will also encounter rooms with the ability to teleport him across portions of the castle and rooms which will restore his health and allow the player to save his or her progress in the game. The game also automatically updates the castle map to reflect Nathan's progress through it. Circle of the Moon incorporates elements found in role-playing games. Nathan possesses various statistics: hit points, the amount of damage he can withstand before dying; magic points, how often he can cast a magical attack; strength, the power of his physical attack; defense, his resilience to damage inflicted by the monsters; intelligence, the recovery speed of magic points; and luck, the frequency with which items are dropped by enemies. Defeated enemies drop various items and equipment, and provide experience points; after reaching a predetermined amount of experience points, Nathan will level up, and his statistics will improve. The defeat of boss enemies allows the player to acquire new abilities to progress further in the game. Unique to Circle of the Moon is the Dual Set-up System (DSS), based on magic cards found throughout the game that belong to one of two categories: Action and Attribute. Each of the ten Action card takes its name from one of the gods and goddesses from Roman mythology, and determines the type of magic being performed, while the ten Attribute cards take their names from creatures from Greek and Roman mythology, and add an effect to the magic. To produce a magical effect, the player combines one card from each of the two categories, for a total of one hundred different combinations. In "The Battle Arena"—a certain area of the castle which consists of seventeen rooms filled with stronger versions of monsters found elsewhere in the castle—Nathan's supply of mind points is drained, causing the DSS cards to become temporarily unusable. Castlevania: Circle of the Moon has four alternative modes of gameplay, which must be completed in order as completion of one mode unlocks the code for the next. Once the player has finished Circle of the Moon for the first time, he or she receives a code that can be entered as his or her name when starting a new game; this code will start the game in Magician Mode, in which Nathan has decreased strength and defense, but increased intelligence and begins with all twenty DSS cards. Fighter Mode does not permit the use of DSS cards, but increases his strength and endurance. Shooter Mode allows a higher maximum of hearts he can carry, but gives a penalty to strength, defense, and hit points. Nathan can throw homing daggers if he collects two daggers in a row in this mode. Thief Mode reduces Nathan's strength and defense, but increases his luck greatly.