The Mayfair Exponential Game System, or MEGS, is a game engine derived from the rules of the superhero role-playing game DC Heroes (1985) by Mayfair Games. It is notable for using a logarithmic (exponential) scale for measuring nearly every statistic in the game.

MEGS was updated in the second and third editions of DC Heroes (1989 and 1993 respectively), and used in the Batman Role-Playing Game (1989). A modified version was also used in the satirical Dark Age superhero game Underground (1993).

After Mayfair stopped publishing DC Heroes games, the rights to the rules were licensed to Pulsar Games, who used the MEGS engine in the superhero RPG The Blood of Heroes (1998). Pulsar Games went out of business in 2004 and the MEGS system has not been used since.

## Mechanics

All measurements in MEGS are done using a logarithmic scale. The units on this scale are called "Attribute Points" or "APs" in the superhero games and simply "Units" in Underground, with each unit on the scale represents exponentially increasing values for length, weight, time, etc. Because of the nature of logarithms and exponents, 0 APs/Units is a meaningful, positive value. Indeed, even negative APs/Units still represent positive values, though exponentially smaller, down to -100 APs, which is defined as absolute zero for all units.

In the superhero games, 1 AP corresponds to 8 seconds, 20 feet (6.1 m), 100 pounds (45 kg), 2 cubic feet (57 L), \$50, or a typed page of information. A single increase of an AP roughly doubles the value, so 2 APs of weight is about 200 pounds, while 6 APs of weight is about 3200 pounds, or about 1.5 tons.

In Underground, 1 Unit corresponds to 5 seconds, 12 feet (3.7 m), 125 pounds (57 kg), 64 cubic feet (1,800 L), or a bit more than a paragraph of text. An increase of 3 Units represents a doubling of the related value, so 4 Units of weight is about 250 pounds, while 7 Units of weight is about 500 pounds.

Multiplication and division of raw values are simplified to addition and subtraction on a logarithmic scale, so the MEGS scale functions essentially the same way that slide rules do. For example, raw distance travelled is normally calculated by multiplying raw speed by raw time. In MEGS, speed and time in APs/Units are simply added together to yield the distance travelled in APs/Units. So a car traveling at a speed of 5 APs (about 55 MPH) for 9 APs of time (about 34 minutes) will travel 5+9=14 APs of distance (about 31 miles). The results of other important game events can be determined in similar ways, such as calculating the distance an object can be thrown (the player character's strength score minus the weight of the object).