Why .mr-* emitted scale keys — and why v3 rewrote the engine.

How the engine does it#

A v2 bug emitted the scale KEY instead of the VALUE for some right/bottom utilities. The fix drove v3's differential testing culture: every utility now has oracle-verified output.

Example#

css
/* v2 emitted: */ .mr-4 { margin-right: 4 } /* key! */
/* v3 emits:  */ .mr-4 { margin-right: 1rem }

From v2 to v3#

Everything in this article survives the upgrade — the v2 → v3 migration guide keeps the generator API stable while fixing spacing and responsive bugs.

Utilities · Themes · Configuration