films, including The Big Boss (1971), in which Lee fights a criminal gang before battling the big boss, and Game of Death (1972), where Lee fights a different boss on each level of a pagoda, which later inspired the boss battles of martial arts action games such as beat 'em ups. Another precursor is tabletop role-playing games starting with Dungeons & Dragons (1974), in which in a typical dungeon campaign there would be one powerful enemy acting as the boss of the weaker minions that players would face beforehand, in the same sense as a crime boss, which later inspired the boss battles of role-playing video games. The first interactive video game to feature a boss was dnd, a 1975 role-playing video game for the PLATO system. One of the earliest dungeon crawls, dnd implemented many of the core concepts of Dungeons & Dragons. The objective of the game is to retrieve an "Orb" from the bottommost dungeon. The orb is kept in a treasure room guarded by a high-level enemy named the Gold Dragon. Only by defeating the Dragon can the player claim the orb, complete the game and be eligible to appear on the high score list. In 1980, boss battles appeared in several arcade action games. In March 1980, Sega released Samurai, a jidaigeki-themed martial arts action game where the player samurai fights a number of swordsmen before confronting a more powerful boss samurai. SNK's Sasuke vs. Commander, released in October 1980, is a ninja-themed shooting game where the player character fights enemy ninjas before confronting bosses with various ninjutsu attacks and enemy patterns. It was one of the earliest games with multiple boss encounters, and one of SNK's earliest games. Phoenix, released in December 1980, is a fixed shooter where the player ship must fight a giant mothership in the fifth and final level. At several points in Namco's vertically scrolling shooter Xevious (1982), the player must defeat an Andor Genesis mothership to advance. In side-scrolling character action games such as beat 'em ups, Irem's 1984 arcade game Kung-Fu Master established the end-of-level boss battle structure used in these games, with the player character progressing through levels (represented by floors of a temple) and fighting a boss character at the end of each level; in turn, this end-of-level boss battle structure was adapted from the Bruce Lee film Game of Death, where Lee's character fights a