While Vampire Killer shares the same premise, soundtrack, characters and locations as the original Castlevania, the structure of the game and its play mechanics differ significantly from its NES counterpart. Like Castlevania, Vampire Killer consists of 18 stages, with a boss encounter at the end of every third stage. But in contrast to the linear level designs in Castlevania, Vampire Killer features more labyrinth-like stages, requiring the player to not only seek out the exit to the next stage, but also the skeleton key required to unlock it. Due to the hardware limitations of the MSX2, Vampire Killer uses flip screens instead of scrolling. The game can be played with a keyboard or a game controller. Items and weapons can be obtained not only by breaking through candle stands and certain walls like in the NES version, but also by purchasing them from merchants hidden throughout the castle or by unlocking treasure chests using keys. Simon's default whip can also be replaced with one of four weapons: a chain whip, throwing daggers, an ax, and a cross - the latter two function both like a boomerang and must be retrieved on their return path if the player wishes to preserve them. There are also four items that Simon can carry with him similar to the sub-weapons in the NES version: a map which shows his current position and the location of the exit, holy water, an hourglass and one of two types of shields. Heart points are used not only as ammunition for the holy water and hourglass, but also as currency for merchants. There are other items that provide more auxiliary effects such as increasing or decreasing the prices of items sold by merchants, temporary invulnerability, increased walking speed and jumping height, and health recovery. After defeating a boss, Simon will start the next stage without any of his previously-accumulated equipment, aside from the number of hearts and the map. The player starts the game with only three lives and with no way to gain extra lives. There are no continues, unless the game is played the Game Master cartridge on the second slot. Playing with the Game Master will also enable the option to select the stage and the number of lives to start with, as well as the ability to skip screens.
