Kojima has cited Yuji Horii's "The Portopia Serial Murder Case" (1983) and Shigeru Miyamoto's "Super Mario Bros." (1985) as the games that inspired him to enter the video game industry. "Portopia Serial Murder Case", a murder mystery adventure game, was an important influence because, according to Kojima, it had "mystery, a 3D dungeon, humor, and a proper background and explanation of why the murderer committed the crime. That is why there was drama in this game. My encountering this game expanded the potential of video games in my mind." "Portopia" had an influence on his early works, including "Metal Gear" and particularly "Snatcher".