FrontendAround since 2017
CSS Custom Properties
Also written as CSS Variables
Reusable values (colors, spacing, fonts) defined once in CSS and referenced throughout a stylesheet — CSS's native answer to what Sass variables used to require a preprocessor for.
Think of it like
Like a paint store's master color-mixing formula — change the formula once, and every can of that color, wherever it was used, updates automatically.
Junior or senior?
Junior sounds like
Reaches for a Sass variable out of habit.
Senior sounds like
Uses native CSS custom properties for theming and can describe building something like light/dark mode with them.
Ask them
“Have you used CSS custom properties to build a theming system, like light/dark mode?”