Understanding the CSS Snippet: ”-sd-animation: sd-fadeIn; –sd-duration: 250ms; –sd-easing: ease-in;”
This small set of CSS custom properties defines a concise, reusable animation pattern that’s easy to apply across components. Below I explain what each piece does, show a practical CSS implementation, and offer variations and accessibility tips to help you use it effectively.
What the properties mean
- -sd-animation: likely a custom shorthand used by a design system (here named “sd”) to select a predefined animation — in this case
sd-fadeIn. - –sd-duration: sets how long the animation runs;
250msis quick and suitable for subtle UI transitions. - –sd-easing: defines the timing function;
ease-inmakes the animation start slowly and speed up.
Example implementation
Use these variables with standard CSS animation properties. Below is a compact example that defines a fade-in keyframes sequence and a utility class that consumes the custom properties.
:root {–sd-duration: 250ms; –sd-easing: ease-in; /* optional fallback if -sd-animation isn’t set on an element / –sd-animation-name: sd-fadeIn;}
/ define the animation /@keyframes sd-fadeIn { from { opacity: 0; transform: translateY(6px); } to { opacity: 1; transform: translateY(0); }}
/ utility that applies the animation using the custom props */.sd-animate { animation-name: var(–sd-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;}
Then use it in HTML:
<div class=“sd-animate” style=”-sd-animation: sd-fadeIn; –sd-duration: 250ms; –sd-easing: ease-in;”> Hello — I fade in!</div>
Note: The custom property name -sd-animation isn’t a standard CSS variable syntax (it uses a single dash prefix). Browsers only recognize custom properties beginning with –. To consume -sd-animation you’d need a preprocessing step (e.g., a build tool that maps -sd-animation to –sd-animation-name) or use it as a project-specific convention parsed by your framework.
Variations
- Slower fade: `–sd-duration: 500ms;
- Softer curve:
–sd-easing: cubic-bezier(0.4, 0, 0.2, 1); - Slide-and-fade from left: change keyframes to translateX(-8px).
Accessibility considerations
- Respect user motion preferences: add
@media (prefers-reduced-motion: reduce)to disable or shorten animations. - Keep animations subtle and avoid long or repetitive motion that can cause discomfort.
Quick accessibility snippet
@media (prefers-reduced-motion: reduce) { .sd-animate { animation: none; transition: none; }}
Use these properties as a compact, design-system-friendly way to standardize transitions across your UI while keeping them configurable per component.
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