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

These CSS custom properties and a shorthand-style declaration define a simple, reusable animation pattern that can be applied to elements for a smooth fade-in effect. Below is a concise guide explaining each part, how to implement it, and practical examples.

What each part means

• -sd-animation: sd-fadeIn;
  • Acts like a custom “animation name” hook used by your CSS/JS system. It signals that the element should use the sd-fadeIn animation pattern.
• –sd-duration: 250ms;
  • A CSS custom property specifying the animation’s duration. Using a variable makes it easy to adjust timing across components.
• –sd-easing: ease-in;
  • A CSS custom property for the timing function, controlling acceleration. ease-in starts slow and speeds up.

Core CSS pattern

Use CSS variables and an @keyframes rule tied to the sd-fadeIn name. Example:

:root {–sd-duration: 250ms;  –sd-easing: ease-in;}
@keyframes sd-fadeIn {  from { opacity: 0; transform: translateY(6px); }  to   { opacity: 1; transform: translateY(0); }}
/* A utility that applies the animation when -sd-animation is set */[data-sd-animation=“sd-fadeIn”],.-sd-animation-sd-fadeIn {  animation-name: sd-fadeIn;  animation-duration: var(–sd-duration, 250ms);  animation-timing-function: var(–sd-easing, ease-in);  animation-fill-mode: both;  will-change: opacity, transform;}

How to apply in HTML

• Using a data attribute:

<div data-sd-animation=“sd-fadeIn”>Fade-in content</div>

• Using a utility class:

<div class=”-sd-animation-sd-fadeIn” style=”–sd-duration: 400ms; –sd-easing: cubic-bezier(.2,.8,.2,1);”>  Slower, custom easing</div>

JavaScript trigger (optional)

If you want to add the animation after mount or on interaction:

function triggerFadeIn(el, duration = ‘250ms’, easing = ‘ease-in’) {  el.style.setProperty(’–sd-duration’, duration);  el.style.setProperty(’–sd-easing’, easing);  el.setAttribute(‘data-sd-animation’, ‘sd-fadeIn’);  // force reflow to restart animation if needed  void el.offsetWidth;}

Accessibility tips

• Keep motion-reduction preferences in mind:

@media (prefers-reduced-motion: reduce) {  [data-sd-animation=“sd-fadeIn”],  .-sd-animation-sd-fadeIn {    animation: none !important;    transition: none !important;  }}

• Use short durations (like 250ms) for quick, non-disruptive motion.

Use cases

• Toasts and notifications
• Modal or panel entrance
• Staggered list reveal (combine with animation-delay)
• Micro-interactions on hover/focus (adjust transform and easing)

Stagger example

.item { opacity: 0; transform: translateY(6px); }.item[data-sd-animation=“sd-fadeIn”] { animation: sd-fadeIn var(–sd-duration) var(–sd-easing) both; }
.item:nth-child(1) { animation-delay: 0ms; }.item:nth-child(2) { animation-delay: 60ms; }.item:nth-child(3) { animation-delay: 120ms; }

Summary

The snippet -sd-animation: sd-fadeIn; –sd-duration: 250ms; –sd-easing: ease-in; encapsulates a compact, customizable fade-in animation pattern. Implement it with CSS variables, respect reduced-motion preferences, and use short durations for unobtrusive UI motion.