Question: Heroes Unlimited is a role-playing game that was written by which American artist and writer?

full_context: Document 1: Keiji Inafune: Keiji Inafune (稲船 敬二 , Inafune Keiji , born 8 May 1965) is a Japanese video game producer, illustrator and businessman. Starting his career at Capcom in the late 1980s, his job was as an artist and illustrator. The first Capcom game he worked on was the original "Street Fighter" in 1987. He was then an illustrator and artist of the "Mega Man" series during the NES and Super NES era. For "Mega Man X", he created and designed the character Zero. After the departure of long time producer Tokuro Fujiwara, Inafune then moved onto the position of producer with his first title being "Mega Man 8" in 1996. In addition to being the producer for "Mega Man X4", "Mega Man X5", the three "Mega Man Legends" games, the "Mega Man Zero" series, and the "Mega Man Battle Network" series. Inafune was also a producer of the "Lost Planet", "Dead Rising" and "Onimusha" series. In 2006, he was promoted to Senior Corporate Officer and the head of Research & Development, in addition to Online Business and Global Head of Production at Capcom.
Document 2: Marvel Super Heroes: The Heroic Role-Playing Game: Marvel Super Heroes: The Heroic Role-Playing Game is a role-playing game supplement published by TSR in 1984 for the "Marvel Super Heroes" role-playing game, and was the debut boxed set for the game.
Document 3: Keith Baker (game designer): Keith Baker (born July 7, 1969) is a game designer and fantasy novel author.
Document 4: Steve Peterson (game designer): Steve Peterson is a game designer who has worked primarily on role-playing games.
Document 5: Kevin Siembieda: Kevin Siembieda (born April 2, 1956) is an American artist, writer, designer and publisher of role-playing games.
Document 6: Neal Stephenson: Neal Town Stephenson (born October 31, 1959) is an American writer and game designer known for his works of speculative fiction.
Document 7: Marvel Heroic Roleplaying: Marvel Heroic Roleplaying (MHRP), is the fourth role playing game set in the Marvel Universe, published Margaret Weis Productions under license from Marvel Comics. It was a fast playing game using the Cortex Plus system, with the first volume published in early 2012. In early 2013 Margaret Weis Productions announced they would not be renewing their license.
Document 8: Jack Kirby: Jack Kirby ( ; born Jacob Kurtzberg ; August 28, 1917 – February 6, 1994) was an American comic book artist, writer, and editor, widely regarded as one of the medium's major innovators and one of its most prolific and influential creators.
Document 9: Champions (role-playing game): Champions is a role-playing game published by Hero Games designed to simulate and function in a four-color superhero comic book world. It was originally created by George MacDonald and Steve Peterson in collaboration with Rob Bell, Bruce Harlick and Ray Greer.
Document 10: Rifts (role-playing game): Rifts is a multi-genre role-playing game created by Kevin Siembieda in August 1990 and published continuously by Palladium Books since then. "Rifts" takes place in a post-apocalyptic future, deriving elements from cyberpunk, science fiction, fantasy, horror, western, mythology and many other genres.
Document 11: Jim Bambra: Jim Bambra (born 1956) is a British designer and reviewer of fantasy roleplaying games (RPG), and a former company director. He is particularly known for his contributions to "Dungeons and Dragons", "Fighting Fantasy", "Warhammer", and "" which was based on the "Star Wars" films. Later he became head of design at MicroProse, then managing director of Pivotal Games, a publisher of video games including "".
Document 12: Robert J. Kuntz: Robert J. Kuntz (born September 23, 1955) is a game designer and author of role-playing game publications. He is best known for his contributions to various "Dungeons & Dragons"-related materials.
Document 13: The Mechanoid Invasion: The Mechanoid Invasion (and its source books, supplements and sequels) was the first role-playing game from Palladium Books, conceived and written by Kevin Siembieda, with contributions from Erick Wujcik.
Document 14: Palladium Books: Palladium Books is a publisher of role-playing games (RPGs) perhaps best known for its popular, expansive "Rifts" series (1990–present). Palladium was founded April 1981 in Detroit, Michigan by current president and lead game designer Kevin Siembieda, and is now based in Westland, Michigan. The company enjoys the support of a small but dedicated fanbase who praise its various game series for their innovative settings and ease of adaptability to various personal preferences, play styles, and power levels.
Document 15: Heroes Unlimited: Heroes Unlimited is a superhero role-playing game written by Kevin Siembieda and first published by Palladium Books in 1984. The game is based upon the Palladium Books Megaversal system and is compatible with other games that use the Palladium system.
ground_truth: Kevin Siembieda