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A little history on both:

Castlevania

The Castlevania series is about a war between the enchanted family of the Belmonts (originally "Belmondo") and Dracula. Almost every hundred years, Dracula is resurrected and it is up to the Belmonts to defeat him before he unleashes his wrath on the entire world.

The series is loosely based on Bram Stoker's novel Dracula. In fact, the novel is included in the official timeline of the series, with Castlevania: Bloodlines taking place shortly afterwards.[1] The connection even goes as far as to claim that Quincy Morris, a character from the novel who lands the final blow against Dracula at the cost of his own life, is in fact a Belmont descendant. Morris is also said to have a son, John, and a grandson, Jonathan, who star in Bloodlines and Portrait of Ruin, respectively. The series also incorporates a variety of other creatures from classic horror fiction, films, fantasy, and mythology. These monsters serve to obstruct the path to Dracula but are rarely tied to the game's plot. More
Contra
The Contra series essentially defined the run and gun computer and video game genre. The games, which are a combination of platform and shoot 'em up, consist of a player-controlled human protagonist who employs rapid-fire rifles to destroy enemies. While there is more emphasis put on shooting than jumping, the player must be able to use jump to gain the right angle to destroy certain enemies and avoid getting shot. Avoidance is essential, as it only takes one hit to kill the player.More