Gamma World - System

System

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.

The seventh version is a 4th Edition D&D genre setting using a modified version of the 4th Edition mechanics. Instead of choosing a character class, a player must roll a twenty-sided die two times and consult an accompanying character origin table. For example, a player might obtain the result "Radioactive Yeti" and gain the powers associated with the "Radioactive" and "Yeti" origins. Two decks of cards are included with the game. One deck represents random Alpha Mutations, which can be drawn to gain temporary powers, and the other contains various Omega Tech, powerful technological devices that could possibly backfire on those that use them. Other deviations from the standard 4th Edition D&D rules include new damage types such as "Radiation", Gamma World-specific skills, and increased lethality. Despite these differences, it is possible to use characters and monsters from a D&D game in Gamma World and vice versa.