Template:Infobox RPG Gamma World is a science fantasy role-playing game, originally designed by James M. Ward and Gary Jaquet, and first published by TSR in 1978. It was the first role-playing game in the post-apocalyptic subgenre.Template:Fact
Gamma World takes place in the mid-25th century, more than a century after nuclear war decimated human civilization. The game's designers took inspiration from the post-apocalyptic novels and movies of the 1950s, 1960s, and 1970s; the first edition rules cite Brian Aldiss's Hothouse, Andre Norton's Star Man's Son (also published as Daybreak - 2250 A.D.), Sterling E. Lanier's Hiero's Journey, and Ralph Bakshi's Wizards.
The war that destroyed civilization in Gamma World is only vaguely described in most editions of the game, and what details are provided change from version to version. (The first two editions place the final war in the years AD 2309-2322, and ascribe the final annihilation to a terrorist group called "The Apocalypse" and the ensuing retaliation by surviving factions.) All editions, however, agree that the war destroyed all government and society beyond a village scale, plunging the world into a Dark Age, where readily available technology is at best quasi-medieval (in the first edition, the crossbow is described as "the ultimate weapon" for most Gamma World societies). The post-apocalyptic inhabitants of Earth now refer to their planet as "Gamma World" (or "Gamma Terra" in later editions).
Gamma World is a chaotic, dangerous environment that little resembles pre-apocalyptic Earth. The weapons unleashed during the final war were strong enough to alter coastlines, level cities, and leave large areas of land lethally radioactive. These future weapons bathed the surviving life of Earth in unspecified forms of radiation and biochemical agents, producing widespread, permanent mutations among humans, animals, and plants. As a result, fantastic mutations such as multiple limbs, super strength, and psychic powers are relatively common. (Random tables of such improbable mutations are a hallmark of every edition of Gamma World.) Many animals and plants are sentient, semi-civilized species competing with surviving humans. Both humans and non-humans have lost most knowledge of the pre-war humans, whom Gamma World's inhabitants refer to as "the Ancients". The only group with significant knowledge of the Ancients are isolated robots and other artificial intelligences that survived the war—though these machines tend to be damaged, in ill-repair, or insanely hostile to organic beings.
Gamma World player characters include unmutated humans (referred to as "Pure Strain Humans" in most editions), mutated humans, sentient animals or plants, and androids. Characters explore Ancient ruins and strange post-apocalyptic societies to gain knowledge of the Ancients and social status for themselves. Common adventure themes involve protecting fragile post-apocalypse societies, retrieving Ancient "artifacts" (science fiction gadgetry such as power armor, laser pistols, and anti-grav sleds), or mere survival against the multifarious dangers of the future (such as gun-toting mutant rabbits, rampaging ancient death machines, or other Gamma Worlders bent on mayhem).
A recurrent source of conflict on Gamma World is the rivalry among the "Cryptic Alliances", semi-secret societies whose ideological agendas—usually verging on monomania—often bring them into conflict with the rest of the Gamma World. For example, the Pure Strain Human "Knights of Genetic Purity" seek to exterminate all mutants, while the all-mutant "Iron Society" wants to eliminate unmutated humans. Other rivalries involve attitudes towards Ancient technology, with some Alliances (such as "The Restorationists") seeking to rebuild Ancient society, while others (such as "The Seekers") want to destroy remaining artifacts.
Throughout the game's many editions, Gamma World has almost always remained strongly influenced by Dungeons & Dragons and other role-playing games of the time. Player characters in both games, for instance, have six Attributes rated on a scale of 3 to 18, randomly generated by rolling six-sided dice. Four of those abilities (Charisma, Constitution, Dexterity, and Intelligence) have the same name and functions in both games, and the Physical Strength and Mental Strength attributes in Gamma World closely parallel Strength and Wisdom in D&D.
Character generation is mostly random, and features one of the game's most distinctive mechanics, the mutation tables. Players who choose to play mutants roll dice to randomly determine their characters' mutations. All versions of Gamma World eschew a realistic portrayal of genetic mutation, instead giving characters fantastic abilities (often resembling comic book superpowers) such as electrical generation, infravision, quills, sonic attacks, multiple limbs, dual brains, total body carapaces, precognition, planar travel, weather manipulation, telepathy, and "life leeching".
Characters in all versions of Gamma World earn experience points during their adventures, which cause the character's Rank (in some editions, Level) to increase. Unlike D&D, however, the first two editions of Gamma World do not use a concept of character class, and increases in Rank do not affect the character's skills or combat abilities. In fact, in the first three editions of the game, character rank is primarily a measure of the character's social prestige.
The game mechanics used for resolving character actions, on the other hand, greatly varied between Gamma World editions. The first two editions, like the early editions of D&D, depend heavily on matrix-based mechanics, where two factors (one representing the actor or attacker, and one representing the opponent) are cross-referenced on a chart. For some actions, such as attacks, the number located on the matrix represents a number the acting player must roll. For other actions (such as determining the result of radiation exposure), the matrix result indicates a non-negotiable result. Gamma World's first two editions had a variety of specialized matrices for different situations (again, closely resembling D&D).
The third edition rules replace specialized matrices with the Action Control Table (ACT), a single, color-coded chart that allowed players to determine whether a character action succeeded, and the degree of success, with a single roll. (The ACT concept is drawn from the Marvel Super Heroes game published by TSR shortly before development of Gamma World's third edition.) The ACT requires the referee to cross-reference the difficulty of a character action with the ability score used to complete that action, determining which column of the ACT is used for that action. The character's player then rolls percentile dice; the result is compared to appropriate column, determining a degree of success or failure and eliminating the need for second result roll (e.g. the damage roll that many games require after a successful combat action).
Gamma World's fourth edition abandoned the Action Control Table in favor of mechanics derived from the Advanced Dungeons & Dragons 2nd Edition rules, although some mechanics presage Alternity and the 3rd edition D&D rules. (For example, Gamma World's 4th edition inverted the Armor Class (AC) scale its predecessors inherited, so that higher AC numbers indicate better armor.) AD&D-borrowed concepts such as character classes and Attribute Checks were also prominent in the 4th edition.
The fifth and sixth versions of Gamma World take the game's tendency of mimicking other games to its logical end, adopting the rules systems of other games wholesale: The fifth edition of the game uses the Alternity rules, while the sixth edition uses the d20 Modern rules. Both of those systems, not coincidentally, use game mechanics inspired by D&D, giving Gamma World characters six ability scores, and measuring character development through increases in character class level.
Gamma World originated with Mutant, a game proposal from an unidentified TSR staffer in the late 1970s.Template:Fact TSR editor Tim Kask turned over the incomplete notes for Mutant to James M. Ward and Gary Jaquet, who drew upon Ward's existing rules for Metamorphosis Alpha to develop Gamma World (Anon 1982). The original Gamma World boxed set (containing a 56-page rulebook, a map of a devastated North America, and dice) was released in 1978. TSR went on to publish three accessories for the 1st edition of the game:
- GW1, Legion of Gold by Gary Gygax, Luke Gygax, and Paul Reiche III (ISBN 0-935696-61-X)
- GW2, Famine in Far-Go by Michael Price (ISBN 0-935696-88-1)
- Gamma World Referee's Screen (ISBN 0-935696-78-4)
At least one other TSR product was announced -- Metamorphosis Alpha to Omega, an adaptation of Metamorphosis Alpha's campaign setting to Gamma World's rules (Anon 1981). Work on the adaptation was halted when a 2nd edition of Gamma World was announced.
The second edition Gamma World boxed set (with rules designed by Ward, Jaquet, and David James Ritchie) was released in 1983. Four accessories were released for this version:
- GW3, The Cleansing War of Garik Blackhand by Michael Price & Garry Spiegle (ISBN 0-88038-015-2)
- GW4, The Mind Masters by Phil Taterczynski" (ISBN 0-88038-029-2)
- GWAC1, Gamma World Referee's Screen and Mini Module" (ISBN 0935696784
- GWAC2, Gamma World Character Sheets (ISBN 0-88038-139-6)
TSR also produced four packs of Gamma World miniatures.  TSR started production on a third adventure module, which was to be assigned the identification code GW5. This module was not published (Williams 1989). However, in 2007 a very professional fan produced work of GW5 was published on the internet. It was based around the only information available for the never released TSR module - that of the working title "Rapture of the Deep".
The 3rd edition of Gamma World was another boxed set, credited to James M. Ward and published in September 1985. It introduced the Action Control Table, a color-coded table use to resolve nearly all actions in the game. (Color-coded tables were something of a trend at TSR in mid-1980s. After 1984's Marvel Super-Heroes proved the viability of the concept, TSR revised Gamma World, Star Frontiers, and Top Secret to use similar tables.) Unfortunately for TSR, this version of the rules became notorious for the number of editorial mistakes, including cross-references to rules that didn't appear in the boxed set. The errors were serious enough that TSR published a Gamma World Rules Supplement containing the "missing" rules. The Rules Supplement was sent to gamers who requested it by mail, and included in reprintings of the boxed set (Ward and Johnson 1986).
The five modules TSR published for Gamma World's 3rd edition introduced the setting's first multi-module metaplot, which involved rebuilding an Ancient space shuttle:
- GW6, Alpha Factor by Kim Eastland (ISBN 0-88038-294-5)
- GW7, Beta Principle by Bruce Nesmith (ISBN 0-88038-404-2)
- GW8, Gamma Base by Kim Eastland (ISBN 0-88038-405-0)
- GW9, Delta Fragment by Kim Eastland (ISBN 0-88038-406-9)
- GW10, Epsilon Cyborgs by Kim Eastland (ISBN 0-88038-477-8)
TSR dropped the 3rd edition of Gamma World from its product line before the multi-module storyline could be completed. A clever fan of the game published an acclaimedTemplate:Fact conclusion to the module series (by closely following Kim Eastland's original storyline) under the title "GW11 Omega Project" in 2003.
Despite its editorial issues, the 3rd edition rules were well-received enough to win the 1986/1987 Gamer's Choice Award for "Best Science-Fiction Roleplaying Game" (Rabe 1987).
The 4th edition of Gamma World (ISBN 1-56076-401-5) was a 128-page softcover book, written by Bruce Nesmith and James M. Ward, published in May 1992 by TSR. This version of the game abandoned the 3rd edition's Action Control Table for mechanics resembling 2nd Edition Advanced Dungeons & Dragons. TSR published five accessories for the 4th edition:
- GWA1, Treasures of the Ancients by Dale "Slade" Henson (ISBN 1560765771
- GWA2, The Overlord of Bonparr by Jack A. Barker (ISBN 1-56076-599-2)
- GWQ1, Mutant Master by Bruce Nesmith (ISBN 1-56076-411-2)
- GWQ2, All Animals Are Equal by Dale "Slade" Henson (ISBN 1-56076-638-7)
- GWQ3, Home Before the Sky Falls by Tim Beach, Paul Riegel, Drew Bittner, and Kim Eastland (ISBN 1-56076-674-3)
TSR's Gamma World development team announced at Gencon 1993 that no further products would be released for the 4th edition. They also announced that TSR had restarted development of Metamorphosis Alpha to Omega, but that the manuscript would be completed using the Amazing Engine rules.
The 5th version of Gamma World was a supplement for the science-fiction game Alternity. (In a nod to Gamma World's reputation for being repeatedly revised, the book's back cover states "That's right, it's the return of the Gamma World".) The Gamma World Campaign Setting (ISBN 0-7869-1629-X) was a 192-page softcover book written by Andy Collins and Jeff Grubb, published in 2000 by Wizards of the Coast (WOTC), only a month after WOTC announced its cancellation of the Alternity line. This version of Gamma World is unique as the only one not to have accessories or supplements.
In September 2002, Omega World, a d20 System mini-game based on Gamma World and written by Jonathan Tweet, was published in Dungeon 94/Polyhedron 153. Tweet does not plan any expansions for the game,  although it received a warm reception from Gamma World fans and players new to the concept alike.
In November 2002, Sword & Sorcery Studios (SSS) announced that it had licensed the Gamma World setting from WOTC in order to produce a sixth version of the game.  SSS's version of the game, which reached the market in 2003, used the d20 Modern system, and mimicked D&D's "three core book" model with three hardcover manuals:
- Gamma World Player's Handbook by Bruce Baugh, Ian Eller, Mikko Rautalahti, and Geoff Skellams (ISBN 1-58846-069-X)
- Gamma World Game Master's Guide by Bruce Baugh, Werner Hagen, Lizard, and Doug Oglesby (ISBN 1-58846-068-1)
- Gamma World Mutants and Machines by David Bolack, Gareth Hanrahan, Patrick O'Duffy, and Chuck Wendig (ISBN 1-58846-067-3)
Sword & Sorcery Studios also published three paperback supplements for the d20 version of Gamma World:
- Gamma World Beyond the Horizon by Ellen Kiley (ISBN 1588469778)
- Gamma World Cryptic Alliances and Unknown Enemies by Owen K. C. Stephens, Alejandro Melchor, and Geoff Skellams (ISBN 1588469662
- Gamma World Out of the Vaults by James Maliszewski, John R. Snead, and Ellen P. Kiley (ISBN 1-58846-022-3)
This new version of the game presented a more sober and serious approach to the concept of a post-nuclear world, at odds with the more light-hearted and adventurous approach taken by previous editions; it was also the first edition of the game to include fantastical nanotechnology on a large scale. In August 2005, White Wolf announced that it was reverting the rights to publish Gamma World products back to Wizards of the Coast, putting the game out of print again.  The Sword & Sorcery Studios products had received a poor critical reception, with longterm fans of the game complaining of poor editing, inconsistent rules, a sparse number of mutations compared with previous editions, and a failure to capture the whimsical, freewheeling atmosphere the line had been known for.Template:Fact Several critics and fans considered Tweet's Omega World to be a superior d20 System treatment of the Gamma World concept. 
Some editions of the Gamma World rulebook include details of an anti-mutant militant organization calling itself the Knights of Genetic Purity, which exists solely and explicitly to be a mustache-twirlingly evil enemy for players of the game to fight. The science-fiction television program Andromeda produced an episode in its second season entitled Immaculate Perception which featured a group called the Knights of Genetic Purity, and having them play exactly the same role in the general scheme of things.
The first printing of the first edition has a "lizard wizard" logo on the box and rulebook. 2nd and 3rd printings of the first edition game have a regular TSR wizard logo and they also state inside the manual which printing number they are.
- Anon 1981. 'RPGA Interview with... Jim Ward.' RPGA News, 3:6-12 (Winter 1981-82).
- Anon 1982. 'RPGA Interview with... "Jake" Jaquet.' Polyhedron, 4:6-10 (1982).
- GamingReport.com: S&S Studios To Publish Gamma World Campaign Setting For d20 Modern, retrieved June 16, 2006.
- Rabe, Jean 1987. 'Notes from HQ,' Polyhedron, 38:3,23 (1987).
- Stuff of Legends - Grenadier Models: Gamma World, retrieved June 16, 2006.
- Stuff of Legends - TSR: Gamma World, retrieved June 16, 2006.
- Sword & Sorcery Online: Arthaus Reverts Rights to RAVENLOFT and GAMMA WORLD to Wizards of the Coast, retrieved June 7, 2006.
- Tweet, Jonathan 2003. JoTW Game OW-FAQ, retrieved June 16, 2006.
- Ward, James and Harold Johnson 1986. 'Gamma III.' Dragon, 117:76-80 (Jan 1986).
- Williams, Skip 1989. 'Advice for All Mutants.' Dragon, 149:28-30 (Sep 1989).