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30-seconds-of-code/snippets/dynamic-shadow.md
2018-10-05 09:23:16 +10:00

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### Dynamic shadow
Creates a shadow similar to `box-shadow` but based on the colors of the element itself.
#### HTML
```html
<div class="dynamic-shadow"></div>
```
#### CSS
```css
.dynamic-shadow {
position: relative;
width: 10rem;
height: 10rem;
background: linear-gradient(75deg, #6d78ff, #00ffb8);
z-index: 1;
}
.dynamic-shadow::after {
content: '';
width: 100%;
height: 100%;
position: absolute;
background: inherit;
top: 0.5rem;
filter: blur(0.4rem);
opacity: 0.7;
z-index: -1;
}
```
#### Demo
#### Explanation
1. `position: relative` on the element establishes a Cartesian positioning context for psuedo-elements.
2. `z-index: 1` establishes a new stacking context.
3. `::after` defines a pseudo-element.
4. `position: absolute` takes the pseudo element out of the flow of the document and positions it in relation to the parent.
5. `width: 100%` and `height: 100%` sizes the pseudo-element to fill its parent's dimensions, making it equal in size.
6. `background: inherit` causes the pseudo-element to inherit the linear gradient specified on the element.
7. `top: 0.5rem` offsets the pseudo-element down slightly from its parent.
8. `filter: blur(0.4rem)` will blur the pseudo-element to create the appearance of a shadow underneath.
9. `opacity: 0.7` makes the pseudo-element partially transparent.
10. `z-index: -1` positions the pseudo-element behind the parent but in front of the background.
#### Browser support
<span class="snippet__support-note">⚠️ Requires prefixes for full support.</span>
- https://caniuse.com/#feat=css-filters
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