Harmony Of Dissonance makes use of a 2D side-scrolling style of gameplay, similar to many of the previous Castlevania video games. The objective of the game is to lead the player-character, Juste Belmont, through the monster-filled castle as he searches for his kidnapped friend. The castle consists of two "layers": Castle A and B. Structurally, each castle has mostly the same room layout, but monster types, items, and other aspects vary between the two versions. Later, the player can use special warp rooms that can teleport Juste to other castle rooms and between castles. The two castles share a connection; for example, the destruction of a wall in one castle can cause a change in the other. The game further divides the castle into various, named areas: the Shrine of the Apostates, for example. Relics and keys found within the castle allow Juste to reach previously inaccessible areas. Harmony Of Dissonance makes use of the forward dash move, which causes Juste to move forward with a short burst of speed. Unique to Harmony Of Dissonance is the ability to collect furniture and collectibles to furnish a bare room that Juste finds in the castle. This, under certain circumstances, does affect the ending. Juste primarily attacks at close quarters using the series' traditional whip weapon, the Vampire Killer. It can be brandished to deflect projectile attacks, reminiscent of Simon Belmont's usage of the weapon in Super Castlevania IV. A variety of ranged sub-weapons—holy water, a dagger, a holy book, a cross, a gem, an axe, and a thunder gauntlet—are available, one of which can be carried at any given time and combined with one of the five spell books—Fire Book, Ice Book, Bolt Book, Wind Book, and the Summoning Tome—hidden throughout the castle to create a magical attack. Casting a spell renders the player character invincible for a moment. Harmony Of Dissonance also makes use of elements found in role-playing games. Defeating minor enemies and bosses will procure experience points for Juste, who will level up when statistical requirements are met. Leveling up will increase his statistics: hit points, the amount of damage the character can receive before dying; magic points, which affects how often he can cast a magical attack; strength, the power of the physical attack; defense, the reduction of damage taken from an enemy; intelligence, the strength of the magical attack; and luck, which determines the rate of items dropped by enemies. Certain relics will also affect his statistics: the Fang of Vlad increases his defense points, for example. Equipment in the form of weapon modifications, armor and accessories can also be found scattered about the castle and will contribute to his statistics. Occasionally, an enemy will drop an item after being killed. Items can also be bought with in-game money from a merchant who appears in various places throughout the castle. Additional modes can be unlocked in the game. For Boss Rush Mode, the player is required to complete the game once and can then fight the bosses from the game in order with the number of bosses depending on the level of difficulty selected. Maxim Mode requires the player to finish the game with the best ending and allows the player to take control of Maxim. Unlike Juste, Maxim cannot equip items and can only use his boomerang as a weapon. Finishing with the best ending also unlocks an option to listen to the music of the game.