An earlier work of Konami that sprang into a widely-known video game series of creepy castles and eerie enemies. Castlevania was the original of them all, and even considered by some to be the best of the NES series.
Konami still hadn't finished developing their masterful graphic techniques at the time of this games release, and it shows. Sure, the graphics look great, but when you play, a lot of the sprites will start to flash or get cut off, etc. when a few are on the screen at a time. Konami was able to fix this later on and allow many sprites on the screen at a time. Castlevania is just an example of their earlier testing to improve upon their games' performance.