The original Castlevania (1986, NES) featured discrete levels that the player completed in a sequential manner. It was followed by Vampire Killer (1986, MSX)[3][4] and Castlevania II: Simon's Quest (1987, NES) which experimented with non-linear adventure gameplay,[5][6] before the series returned to the more linear style of the original Castlevania. Series lead Koji Igarashi found that as they continued to produce sequels to cater to fans of the series, experienced players would race through the levels, while new players to the series would struggle with some stages.[7] To try to make a title that would be more widely appreciated across play levels and extend the gameplay time of the title, Igarashi and others on his team looked toward the ideas used by The Legend of Zelda series into the development of Castlevania: Symphony of the Night (1997, PlayStation); such ideas included a large open world to explore, the need to acquire key items to enter certain areas, and the ability to improve the player-character as one would in console role-playing games.[7][8] The change proved popular with players, and subsequent games in the series would follow this formula.[1] With the releases of Super Metroid and Castlevania: Symphony of the Night, the formula these games presented would form the foundations of what are considered Metroidvanias today.[1] Castlevania: Symphony of the Night had also become a critical and financial success over time, establishing that there was a desire by players for Metroidvania-style games.[9]