RegressionCurve

MMO\rpg\xp · 1 symbol · generated 5 Oct 2026

class

RegressionCurve

Regression (extinction curve). The genuine inverse of a growth S-curve — not just "decreasing," but shaped like one flipped upside down: cost starts near a ceiling, holds high through an initial resistance phase, then drops rapidly through a breakthrough zone, and settles at a low floor. Built for objectives framed as reducing or extinguishing a behavior, where "level" = a milestone of reduction achieved — early reduction is disproportionately hard, then it gets much easier once the behavior loses its grip.

class MMO\rpg\xp\RegressionCurve implements MMO\rpg\xp\iCurve

Namespace: MMO\rpg\xp
Implements: iCurve

XP(n) = floor + (ceiling - floor) / (1 + e^(steepness * (n - midpoint))) (Same logistic denominator as Habit/Logistic, but WITHOUT the negative sign on steepness — that sign flip is what turns the ascending S descending.)

Methods1

xpForLevel($n, $params)

Curves.php:192

function xpForLevel(int $n, array $params): float

$n	int
$params	array
returns	float