Most game situations are resolved by rolling percentile dice and comparing the results against a column of the colorful "Universal Results Table". The column used is determined by the attribute used; different tasks are resolved by reference to different attributes. All characters have seven basic attributes:
Fighting, which determines hit probability in and defense against hand-to-hand attacks.
Agility, which determines hit probability in and defense against ranged attacks, feats of agility vs. the environment, and similar acrobatics.
Strength, which determines damage inflicted by hand-to-hand attacks as well as the success of tasks such as grappling or the lifting and breaking of heavy objects.
Endurance, which determines resistance to physical damage (e.g., poison, disease, death) it also determined how long a character can fight and how fast a character could move at top speed by exerting themselves.
Reason, which determines the success of tasks relating to knowledge, puzzle-solving, and advanced technology.
Intuition, which determines the success of tasks relating to awareness, perception, and instinct.
Psyche, which determines the success of tasks relating to willpower, psionics, and magic.
Players sometimes refer to this set of attributes, or the game system as a whole, by the acronym "FASERIP". Attribute scores for the majority of characters range from 1 to 100, where normal human ability is 6, and peak (non-superheroic) human ability is 30. However, the designers minimize use of the numerical figures, instead preferring adjectives in the Marvel Comics tradition, such as "Incredible" (scores from 36-45) and "Amazing" (46-62). A "Typical" (5-7) attribute has a 50% base chance for success at most tasks relating to that attribute. For example, a character with "Typical" fighting skill has a base chance of 50% to connect with a punch. As an attribute increases, the chance of success increases by about 5% per 10 points. Thus a character with an "Amazing" (50) attribute has a 75% chance of success at tasks relating to that attribute.
Beyond the seven attributes, characters possessed superpowers, such as Spider-Man's wall crawling, or Mister Fantastic's elasticity. The powers function on a mostly ad hoc basis, and thus each character's description gives considerable space to a description of how his or her powers work in the game.
Each character had an origin, which put ceilings on a character's abilities and superpowers. The origins included: Altered Humans (normal people who acquired powers, such as Spider-Man or the Fantastic Four), High-Tech Wonders (normal people whose powers come from devices, e.g., Iron Man), Mutants (persons born with superpowers, such as the X-Men), Robots (created beings such as the Vision and Ultron), and Aliens (a blanket term used to cover non-humans, including extra-dimensional beings such as Thor and Hercules).
The game also featured a simple skill system, referred to as Talents. Talents had to be learned and covered a wide range of knowledges from Archery to Zoology. A Talent raised a character's ability by one rank when attempting actions related to that Talent. For example, a character uses his Agility score when attempting ranged attacks. A character with an Agility of Excellent would normally roll on that column when attacking with a rifle. However, if he had the "Guns" Talent he would treat his Agility as the next higher power rank (Remarkable). The GM was free to determine if a character would be unable to attempt an action without the appropriate Talent (such as a character with no medical background attempting to make a pill that can cure a rare disease).
Resources and Popularity
Characters also had two variable attributes: Resources and Popularity. These attributes were described using the same terms as the character's seven attributes ("Poor," "Amazing," "Unearthly," etc.). But unlike the seven physical and mental attributes which changed very slowly, if at all, Resources and Popularity could change very quickly.
The first of the variables, Resources, represented the character's wealth and ability to obtain goods or services. Rather than have the player keep track of how much money the character had in the bank or with him, the Advanced Game assumed the character had enough money coming in to cover his basic living expenses. The Resources ability was used when the character wished to purchase something out of the ordinary like a new car or house. For example, the referee might decide a character with Typical resources would probably be unable to purchase a brand new sports car, but with a Yellow Resources roll might be able to afford a used car in good condition. The game books note that a character's Resources score can change for a variety of reasons, such as winning the lottery or having a major business transaction go bad.
The second variable, Popularity, reflected how much the character was liked (or disliked) in the Marvel Universe. Popularity could be used to influence non-player characters. A superhero with a high rating, like Captain America (whose popularity is Unearthly-the highest most characters can achieve), might be able to use his Popularity to gain entrance to a club because the general population of the Marvel Universe admires him. If he were to try the same thing as his secret identity Steve Rogers (whose Popularity is only Typical), he would probably be unable to do it. Villains also had a Popularity score, which was usually negative (a bouncer might let Doctor Doom or Magneto into the aforementioned club simply out of fear). There were several ways Popularity could change. For example, if Doctor Doom defeated Spider-Man in front of the general public, Spidey's Popularity would go down for a short time. But if everyone's favorite web-slinger managed to foil one of Doctor Doom's plans and the word got out, he would enjoy a temporary Popularity boost. Since mutants were generally feared and distrusted in the Marvel Universe, these characters start with a Popularity of 0 and have a hard time improving this attribute.
The game was intended to be played using existing Marvel characters as the heroes. The Basic and Advanced Sets both contained fairly simple systems for creating original superheroes, based on random ability rolls (a la Dungeons & Dragons). In addition, the Basic Set Campaign Book also allowed players to create original heroes by simply describing the desired kind of hero, and working together with the GM to assign the appropriate abilities, powers, and talents.
The game's equivalent of experience points was Karma, a pool of points initially determined as the sum of a character's three mental attributes (Reason, Intuition, and Psyche).
The basic system allowed players to increase their chances of success at most tasks by spending points of Karma. For example, a player who wanted to make sure he would hit a villain in a critical situation could spend however many Karma points were necessary to raise the dice roll to the desired result. Additional Karma points were distributed by the referee at the end of game sessions, typically as rewards for accomplishing heroic goals, such as defeating villains, saving innocents, and foiling crimes. Conversely, Karma could be lost for unheroic actions such as fleeing from a villain, or failing to stop a crime: in fact, in a notable departure from many RPGs (but strongly in keeping with the genre), all Karma was lost if a hero killed someone or allowed someone to die.
In the Advanced Game, Karma points could also be spent to permanently increase character attributes and powers (at a relatively moderate cost, ten times the attribute number raised, powers were steeper, at twenty times the number). The Karma system thus united two RPG mechanics—"Action" or "Hero" points (which allow players to control random outcomes) and character advancement (e.g., "experience points")—in one system. Though this system could frustrate both referees and players (the former because a player willing and able to spend Karma could effectively overcome any challenge at least once; the latter because advancement was slow compared with most other RPGs), it had the virtue of emulating two central features of super-hero comics, namely, that heroes almost always win, even in improbable circumstances, and that heroes' power levels remain mostly static. Furthermore, the system encouraged players to keep their characters' behavior to the equivalent concept of their alignment by giving an incentive to behave heroically and morally correct.
Marvel Superheroes was driven by two primary game mechanics: column shifts and colored results. Both essentially influenced the difficulty of an action.
A column shift is used when a character is attempting an exceptionally hard or easy action. A column shift to the left indicates a penalty, while a shift to the right indicates a bonus. For example, Reed Richards (Mr. Fantastic) has an Intuition of Excellent, making him significantly more perceptive than the average person whose Intuition is Typical (two ranks lower). The GM might determine that spotting a trap hidden beneath a few sticks and leaves will be fairly easy, and give the player running Mr. Fantastic a +1 column shift. His Intuition will be treated as Remarkable (the next column to the right). However, a trap buried underground might be considerably harder to spot, and the GM might give the player a -1 column shift penalty. In this case, Mr. Fantastic's Intuition will only be treated as Good (the column to the left).
The column for each ability is divided into four colors: white, green, yellow, and red. A white result is always a failure or unfavorable outcome. In most cases, getting a green result was all that was needed to succeed at a particular action. Yellow and red results usually indicated more favorable results that could knock back, stun, or even kill an opponent. However, the GM could determine that succeeding at an exceptionally hard task might require a yellow or red result.
Additional rules in the "Campaign Book" of the Basic Set, and the subsequent Advanced Set, used the same game mechanic to resolve non-violent tasks. For example, if a superhero needs to figure out how to operate a piece of alien technology, the hero would have to succeed at a Reason roll, where the chance of success is modified by the complexity of the device.