-sd-animation: sd-fadeIn; –sd-duration: 250ms; –sd-easing: ease-in;

Understanding the CSS Custom Properties: ”-sd-animation: sd-fadeIn; –sd-duration: 0ms; –sd-easing: ease-in;”

CSS custom properties (variables) let developers define reusable values and tweak component behavior without changing multiple rules. The snippet -sd-animation: sd-fadeIn; –sd-duration: 0ms; –sd-easing: ease-in; appears to be a set of such properties used to control an animation system—likely within a design system, component library, or custom UI framework that recognizes -sd- prefixed variables.

What each property likely means

• -sd-animation: sd-fadeIn;
  • Assigns a named animation (here sd-fadeIn) to the element. The -sd- prefix suggests these variables are scoped to a specific design system or component toolkit.
• –sd-duration: 0ms;
  • Sets the animation duration to zero milliseconds. Effectively, this disables the visible transition, causing the animation to complete instantly. This is useful for rendering elements in their final state without a perceptible transition—e.g., instant mode for accessibility or testing.
• –sd-easing: ease-in;
  • Defines the timing function for the animation. ease-in makes the animation start slowly and accelerate toward the end. With a 0ms duration this has no visual effect, but it documents the intended easing when duration is changed.

Typical use cases

1. Design system defaults
   • Components can expose -sd- variables so app-level styles override animations consistently across the UI.
2. Accessibility / reduced-motion
   • Setting –sd-duration: 0ms is a technique to honor users’ reduced-motion preferences or provide a “no-animation” state for testing or performance.
3. Theming and runtime control
   • Developers can toggle the animation name, duration, or easing at runtime (via JS or CSS media queries) to create different interaction modes.
4. Animation composition
   • A named animation like sd-fadeIn can map to a keyframe set elsewhere; variables keep components decoupled from implementation details.

Example implementation

Below is a simple example showing how these variables might be used with CSS keyframes and a component:

:root {–sd-duration: 300ms;  –sd-easing: ease-out;  -sd-animation: sd-fadeIn;}
/* Named keyframes /@keyframes sd-fadeIn {  from { opacity: 0; transform: translateY(8px); }  to   { opacity: 1; transform: translateY(0); }}
/ Component using variables /.card {  animation-name: var(-sd-animation);  animation-duration: var(–sd-duration);  animation-timing-function: var(–sd-easing);  animation-fill-mode: both;}
/ Instant/no-animation mode */.no-anim .card {  –sd-duration: 0ms;  –sd-easing: ease-in;}

Best practices

• Use descriptive variable names