CSS-in-JS compiler that converts JavaScript objects to CSS. Use when: (1) User mentions "esm-styles" explicitly (2) Working with .styles.mjs files (3) Project has esm-styles.config.js CRITICAL: This is NOT Tailwind/SCSS - no utility classes, no & ampersand syntax.
Write CSS as JavaScript objects. The compiler converts JS → CSS.
// ❌ WRONG - will NOT work