-sd-animation: sd-fadeIn; –sd-duration: 0ms; –sd-easing: ease-in;

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

This article explains what the CSS-like shorthand shown in the title represents, when and how to use it, and practical patterns for implementing similar animation variables in modern front-end projects.

What this syntax is

• Custom properties (CSS variables): The double-dash prefix (–) marks CSS custom properties. They hold values you can reference elsewhere with var().
• Namespacing convention: The leading -sd- looks like a namespace or design-system prefix to avoid collisions with other variables.
• Animation intent: sd-fadeIn likely names an animation or keyframe behavior. The other properties declare duration and easing.

Why use this pattern

• Reusability: Centralize animation values to keep motion consistent across components.
• Theming: Swap variable values for different themes or motion preferences.
• Maintainability: Changing the variable updates all components that use it.

How to implement (example patterns)

1. Define keyframes and a mapping for semantic animation names:

@keyframes sd-fadeIn {from { opacity: 0; transform: translateY(6px); }  to   { opacity: 1; transform: translateY(0); }}
:root {  –sd-animation: sd-fadeIn;  –sd-duration: 250ms;  –sd-easing: ease-in;}

2. Apply variables in a component:

.card {  animation-name: var(–sd-animation);  animation-duration: var(–sd-duration);  animation-timing-function: var(–sd-easing);  animation-fill-mode: both;}

3. Component-level overrides:

.modal {  –sd-duration: 150ms;  –sd-easing: cubic-bezier(.2, .8, .2, 1);}

4. Respect user motion preferences:

@media (prefers-reduced-motion: reduce) {  :root { –sd-duration: 0ms; }  .card { animation: none; transition: none; }}

Advanced patterns

• Multiple animations: Store a full shorthand in one variable: –sd-animation: sd-fadeIn 250ms ease-in both; then apply with animation: var(–sd-animation);
• JS-driven swaps: Toggle CSS variable values from JavaScript for runtime control:

el.style.setProperty(’–sd-animation’, ‘sd-slideIn’);el.style.setProperty(’–sd-duration’, ‘350ms’);

• Design tokens: Export these variables from a design-token system so motion scales with brand guidelines.

Troubleshooting

• If animation-name seems ignored, ensure the keyframes name matches the variable value exactly.
• Check specificity: component-level variables override root ones.
• Animations don’t run on display: none; use visibility/opacity instead.

Best practices

• Use short durations for micro-interactions (100–250ms), longer for larger transitions (300–500ms).
• Prefer easing curves that match the intent: ease-out for entrance, ease-in for exits.
• Always honor prefers-reduced-motion.

Conclusion

The snippet -sd-animation: sd-fadeIn; –sd-duration: 250ms; –sd-easing: ease-in; is a compact, maintainable way to express animation intent using CSS custom properties. Use it to centralize motion, enable theming, and keep UI transitions consistent across your project.