DC Heroes uses the original Mayfair Exponential Game System. Characters have nine Attributes, divided into two axes. The first axis defines Attributes as being Physical, Mental, or Mystical. The second axis divides them into Action, Effect, and Resistance Attributes.
- Dexterity (Action): Quick reflexes, like the Green Arrow.
- Strength (Effect): Muscle and power, like Superman.
- Body (Resistance): Toughness. Superman has a high toughness.
- Intelligence (Action): Governs perception and many skill uses.
- Will (Effect): Force of will and ability to maintain concentration. The Green Lantern has a high Will.
- Mind (Resistance): Mental resilience, sanity, and memory.
- Influence (Action): Charm and the ability to manipulate mystical forces.
- Aura (Effect): Force of personality and mystical power.
- Spirit (Resistance): Spiritual resolve.
A normal human has 2 AP's (Attribute Points) in each Attribute. Each AP doubles the previous value, so someone with a Strength of 4 is four times as strong as someone with a Strength of 2. To perform an action, an Action Attribute is rolled against another Action Attribute (which serves as the Opposing Value for the test). Two ten-sided dice are rolled. If the total equals or succeeds a target number on a chart, the Effect Value is compared to the Resistance Value. For instance, Dexterity is used against Dexterity to hit, and if you hit, Strength is compared to Body to determine how much damage you cause.
Rolling doubles allows you to roll again, but double 1's causes an automatic failure. Characters also have Hero Points which can be used to aid rolls or reduce damage. Especially good rolls can result in Column Shifts, which reduce the relative Resistance, allowing for more spectacular results.
All actions, from combat to persuasion to detective work, use the same system. Further, everything is measured in APs. 10 APs is a mile of distance. 6 APs is over a ton of weight. This allows measures to be quickly converted, and many comparisons can be done on the fly.
Characters also have Skills and Powers. Later editions added Advantages and Drawbacks. Characters might also have Limitations on their powers. Each character also has a Alignment that describes how and why they perform heroic actions (or villainous ones in the case of the bad guys).