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

Context articles: Marvel Super Heroes: The Heroic Role-Playing Game
Space Opera (role-playing game)
Capes
Robert N. Charrette
The Legend of Heroes: A Tear of Vermillion
Bunnies &amp; Burrows
Heroes Unlimited
Kevin Siembieda
Bill Coffin
Marvel Super Heroes Advanced Set

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.
Space Opera is a science-fiction role-playing game created by Edward E. Simbalist, A. Mark Ratner, and Phil McGregor in 1980 for Fantasy Games Unlimited.
 While the system is applicable to the whole genre of science fiction, "Space Opera" had a default setting intended to be used as generic science fiction role-playing game rules, the focus being on creating space opera themed adventures.
Capes is a role-playing game by Tony Lower-Basch, independently published by Muse of Fire Games.
 It is a superhero role-playing game played in "scenes", in which players choose what character to play before each new scene.
 The game is a competitive storytelling game without a GM.
 Players create and play the villains who oppose other players' heroes.
Robert N. Charrette (born 1953) is an award-winning graphic artist, game designer, sculptor and author.
 Charrette has authored more than a dozen novels.
 His gaming materials have received many Origins Awards.
 Charrette was inducted in the Origins Hall of Fame in 2003.
 His work is known for a clean, realistic style that invokes themes from Feudal Japan and Chanbara films and in particular, historical and fantastic representations of Samurai culture.
 His early work in game design and miniature sculpting set the tone for depictions of Japanese mythology in American fantasy and science fiction.
 His 1979 role-playing game "Bushido" was one of the first role-playing games with a non-Western theme and remained in print for more than three decades.
 Charrette produced gaming products for Fantasy Games Unlimited, Grenadier Models Inc. and Ral Partha Enterprises, FASA and currently operates Parroom Enterprises, LLC, a boutique miniatures game company.
The Legend of Heroes: A Tear of Vermillion, known as "Eiyū Densetsu IV Akai Shizuku" (英雄伝説IV 朱紅い雫 , Eiyū Densetsu Fō Akai Shizuku ) in Japan is a role-playing game originally developed by Nihon Falcom Corporation.
 It is the fourth game in the "The Legend of Heroes" series, and the second in the ""Gagharv Trilogy"".
 This game is a remake of the original game released for the NEC PC-9801 in 1996.
 It was also released in 1998 for the PlayStation and a 1999 release for Microsoft Windows PCs.
 This game was the first US-released "Legend of Heroes" game since "" for the TurboGrafx-16.
 The US release dropped the number from the title, and was known as simply ""The Legend of Heroes: A Tear of Vermillion"".
Bunnies & Burrows ("B&B") is a role-playing game (RPG) inspired by the novel "Watership Down".
 Published by Fantasy Games Unlimited in 1976, the game centered on intelligent rabbits.
 It introduced several innovations to role-playing game design, being the first game to allow players to have non-humanoid roles, and the first to have detailed martial arts and skill systems.
 Fantasy Games Unlimited published a second edition of the game in 1982, and the game was modified and republished by Steve Jackson Games as an official "GURPS" supplement in 1992.
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.
Kevin Siembieda (born April 2, 1956) is an American artist, writer, designer and publisher of role-playing games.
Bill Coffin is a writer of novels and role-playing games in the fantasy and science fiction genres.
 Perhaps best known for his work at Palladium Books from July 1998 through May 2002, he made significant contributions to several of Palladium's game series, most notably "Palladium Fantasy", but also "Heroes Unlimited" and "Rifts", and created his own game, "Systems Failure".
Marvel Super Heroes Advanced Set is a role-playing game supplement published by TSR in 1986 for the "Marvel Super Heroes" role-playing game.