Those are custom CSS properties (CSS variables) likely used by a design system or component library to control a small animation. Brief breakdown:
- -sd-animation: sd-fadeIn;
- Specifies the animation name to apply (here a custom animation called “sd-fadeIn”).
- –sd-duration: 250ms;
- Sets the animation duration to 250 milliseconds.
- –sd-easing: ease-in;
- Sets the timing function (acceleration curve) to ease-in, which starts slowly and speeds up.
How they’re used (typical patterns):
- Defined on an element or root and consumed by component styles:
- animation: var(–sd-animation) var(–sd-duration) var(–sd-easing) both;
- The actual keyframes must exist, e.g.:
- @keyframes sd-fadeIn { from { opacity: 0; transform: translateY(4px); } to { opacity: 1; transform: translateY(0); } }
Notes:
- Leading hyphen in -sd-animation suggests a private or vendor-like custom property but functions same as –name; however standard custom properties must start with –, so -sd-animation is just a normal property name (not usable with var()) unless defined that way — prefer starting with – (e.g., –sd-animation).
- Use prefers-reduced-motion media query to respect accessibility:
- @media (prefers-reduced-motion: reduce) { animation: none; transition: none; }
If you want, I can:
- Provide a ready-to-use CSS snippet implementing sd-fadeIn with these variables.
- Convert to a scoped component (e.g., Web Component, React styled-component) or show how to toggle via JS.
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