Complementary stats are statistics that always combine to a fixed total, i.e. they are complements of each other. The stat values may change over the course of a session or campaign, but only if other stats change in an equal and opposite way.
Complementary stats are most straightforward and most common when they appear in pairs. There are two forms of paired stats.
- The stats may have a single number which divides the possible total outcomes. In this situation, a roll-under check is used when one stat applies, and a roll-over check is used when the other stat applies. Rolling exactly the number may have other effects. This is the form used in Trollbabe by Ron Edwards and in Lasers & Feelings by John Harper.
- The stats may be numbered separately but be connected such that increase in one of the stats leads to an equal decrease in the other, and vice versa. This is the form used in Honey Heist by Grant Howitt.
Paired complementary stats are particularly useful in a role-playing game that is intended to explore a specific duality, either in the characters (as in Trollbabe and Honey Heist) or in the theme and setting (as in Lasers & Feelings).
Three or more complementary statsEdit
It is possible to have a trait set of three or more complementary stats. Labels in Masks are like complementary stats, in that one must increase whenever another decreases, although it is possible to occasionally increase the overall stat total through character advancement.