duy-nv/30SecondsOfCss

Box-sizing reset

Resets the box-model so that widths and heights are not affected by their borders or padding.

CSS

html {
  box-sizing: border-box;
}

*,
*::before,
*::after {
  box-sizing: inherit;
}

Demo

Explanation

box-sizing: border-box makes the addition of padding or borders not affect an element's width or height.
box-sizing: inherit makes an element respect its parent's box-sizing rule.

Browser support

✅ No caveats.

https://caniuse.com/#feat=css3-boxsizing

Clearfix

Ensures that an element self-clears its children.

Note: This is only useful if you are still using float to build layouts. Please consider using a modern approach with flexbox layout or grid layout.

HTML

<div class="clearfix">
  <div class="floated">float a</div>
  <div class="floated">float b</div>
  <div class="floated">float c</div>
</div>

CSS

.clearfix::after {
  content: '';
  display: block;
  clear: both;
}

.floated {
  float: left;
}

Demo

float a

float b

float c

Explanation

.clearfix::after defines a pseudo-element.
content: '' allows the pseudo-element to affect layout.
clear: both indicates that the left, right or both sides of the element cannot be adjacent to earlier floated elements within the same block formatting context.

Browser support

⚠️ For this snippet to work properly you need to ensure that there are no non-floating children in the container and that there are no tall floats before the clearfixed container but in the same formatting context (e.g. floated columns).

Constant width to height ratio

Given an element of variable width, it will ensure its height remains proportionate in a responsive fashion (i.e., its width to height ratio remains constant).

HTML

<div class="constant-width-to-height-ratio"></div>

CSS

.constant-width-to-height-ratio {
  background: #333;
  width: 50%;
}
.constant-width-to-height-ratio::before {
  content: '';
  display: block;
  padding-top: 100%;
  float: left;
}
.constant-width-to-height-ratio::after {
  content: '';
  display: block;
  clear: both;
}

Demo

Resize your browser window to see the proportion of the element remain the same.

Explanation

padding-top on the ::before pseudo-element causes the height of the element to equal a percentage of its width. 100% therefore means the element's height will always be 100% of the width, creating a responsive square.

This method also allows content to be placed inside the element normally.

Browser support

✅ No caveats.

Evenly distributed children

Evenly distributes child elements within a parent element.

HTML

<div class="evenly-distributed-children">
  <p>Item1</p>
  <p>Item2</p>
  <p>Item3</p>
</div>

CSS

.evenly-distributed-children {
  display: flex;
  justify-content: space-between;
}

Demo

Item1

Item2

Item3

Explanation

display: flex enables flexbox.
justify-content: space-between evenly distributes child elements horizontally. The first item is positioned at the left edge, while the last item is positioned at the right edge.

Alternatively, use justify-content: space-around to distribute the children with space around them, rather than between them.

Browser support

⚠️ Needs prefixes for full support.

https://caniuse.com/#feat=flexbox

Flexbox centering

Horizontally and vertically centers a child element within a parent element using flexbox.

HTML

<div class="flexbox-centering">
  <div class="child">Centered content.</div>
</div>

CSS

.flexbox-centering {
  display: flex;
  justify-content: center;
  align-items: center;
}

Demo

Centered content.

Explanation

display: flex enables flexbox.
justify-content: center centers the child horizontally.
align-items: center centers the child vertically.

Browser support

⚠️ Needs prefixes for full support.

https://caniuse.com/#feat=flexbox

Grid centering

Horizontally and vertically centers a child element within a parent element using grid.

HTML

<div class="grid-centering">
  <div class="child">Centered content.</div>
</div>

CSS

.grid-centering {
  display: grid;
  justify-content: center;
  align-items: center;
}

Demo

Centered content.

Explanation

display: grid enables grid.
justify-content: center centers the child horizontally.
align-items: center centers the child vertically.

Browser support

✅ No caveats.

https://caniuse.com/#feat=css-grid

Grid layout

Basic website layout using grid.

HTML

<div class="grid-layout">
  <div class="header">Header</div>
  <div class="sidebar">Sidebar</div>
  <div class="content">
    Content
    <br>
    Lorem ipsum dolor sit amet, consectetur adipisicing elit.
  </div>
  <div class="footer">Footer</div>
</div>

CSS

.grid-layout {
  display: grid;
  grid-gap: 10px;
  grid-template-columns: repeat(3, 1fr);
  grid-template-areas:
    'sidebar header header'
    'sidebar content content'
    'sidebar footer  footer';
  color: white;
}
.grid-layout > div {
  background: #333;
  padding: 10px;
}
.sidebar {
  grid-area: sidebar;
}
.content {
  grid-area: content;
}
.header {
  grid-area: header;
}
.footer {
  grid-area: footer;
}

Demo

Header

Sidebar

Content
Lorem ipsum dolor sit amet, consectetur adipisicing elit.

Footer

Explanation

display: grid enables grid.
grid-gap: 10px defines spacing between the elements.
grid-template-columns: repeat(3, 1fr) defines 3 columns of the same size.
grid-template-areas defines the names of grid areas.
grid-area: sidebar makes the element use the area with the name sidebar.

Browser support

✅ No caveats.

https://caniuse.com/#feat=css-grid

Truncate text

If the text is longer than one line, it will be truncated and end with an ellipsis ….

HTML

<p class="truncate-text">If I exceed one line's width, I will be truncated.</p>

CSS

.truncate-text {
  overflow: hidden;
  white-space: nowrap;
  text-overflow: ellipsis;
  width: 200px;
}

Demo

This text will be truncated if it exceeds 200px in width.

Explanation

overflow: hidden prevents the text from overflowing its dimensions (for a block, 100% width and auto height).
white-space: nowrap prevents the text from exceeding one line in height.
text-overflow: ellipsis makes it so that if the text exceeds its dimensions, it will end with an ellipsis.
width: 200px; ensures the element has a dimension, to know when to get ellipsis

Browser support

⚠️ Only works for single line elements.

https://caniuse.com/#feat=text-overflow

Circle

Creates a circle shape with pure CSS.

HTML

<div class="circle"></div>

CSS

.circle {
  border-radius: 50%;
  width: 2rem;
  height: 2rem;
  background: #333;
}

Demo

Explanation

border-radius: 50% curves the borders of an element to create a circle.

Since a circle has the same radius at any given point, the width and height must be the same. Differing values will create an ellipse.

Browser support

✅ No caveats.

https://caniuse.com/#feat=border-radius

Custom scrollbar

Customizes the scrollbar style for the document and elements with scrollable overflow, on WebKit platforms.

HTML

<div class="custom-scrollbar">
  <p>Lorem ipsum dolor sit amet consectetur adipisicing elit. Iure id exercitationem nulla qui repellat laborum vitae, molestias tempora velit natus. Quas, assumenda nisi. Quisquam enim qui iure, consequatur velit sit?</p>
</div>

CSS

/* Document scrollbar */
::-webkit-scrollbar {
  width: 8px;
}

::-webkit-scrollbar-track {
  box-shadow: inset 0 0 6px rgba(0, 0, 0, 0.3);
  border-radius: 10px;
}

::-webkit-scrollbar-thumb {
  border-radius: 10px;
  box-shadow: inset 0 0 6px rgba(0, 0, 0, 0.5);
}

/* Scrollable element */
.some-element::webkit-scrollbar {
}

Demo

Lorem ipsum dolor sit amet consectetur adipisicing elit. Iure id exercitationem nulla qui repellat laborum vitae, molestias tempora velit natus. Quas, assumenda nisi. Quisquam enim qui iure, consequatur velit sit?

Explanation

::-webkit-scrollbar targets the whole scrollbar element.
::-webkit-scrollbar-track targets only the scrollbar track.
::-webkit-scrollbar-thumb targets the scrollbar thumb.

There are many other pseudo-elements that you can use to style scrollbars. For more info, visit the WebKit Blog

Browser support

⚠️ Scrollbar styling doesn't appear to be on any standards track.

https://caniuse.com/#feat=css-scrollbar

Custom text selection

Changes the styling of text selection.

HTML

<p class="custom-text-selection">Select some of this text.</p>

CSS

::selection {
  background: aquamarine;
  color: black;
}
.custom-text-selection::selection {
  background: deeppink;
  color: white;
}

Demo

Select some of this text.

Explanation

::selection defines a pseudo selector on an element to style text within it when selected. Note that if you don't combine any other selector your style will be applied at document root level, to any selectable element.

Browser support

⚠️ Requires prefixes for full support and is not actually in any specification.

https://caniuse.com/#feat=css-selection

Dynamic shadow

Creates a shadow similar to box-shadow but based on the colors of the element itself.

HTML

<div class="dynamic-shadow-parent">
  <div class="dynamic-shadow"></div>
</div>

CSS

.dynamic-shadow-parent {
  position: relative;
  z-index: 1;
}
.dynamic-shadow {
  position: relative;
  width: 10rem;
  height: 10rem;
  background: linear-gradient(75deg, #6d78ff, #00ffb8);
}
.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

The snippet requires a somewhat complex case of stacking contexts to get right, such that the pseudo-element will be positioned underneath the element itself while still being visible.

position: relative on the parent establishes a Cartesian positioning context for child elements.
z-index: 1 establishes a new stacking context.
position: relative on the child establishes a positioning context for pseudo-elements.
::after defines a pseudo-element.
position: absolute takes the pseudo element out of the flow of the document and positions it in relation to the parent.
width: 100% and height: 100% sizes the pseudo-element to fill its parent's dimensions, making it equal in size.
background: inherit causes the pseudo-element to inherit the linear gradient specified on the element.
top: 0.5rem offsets the pseudo-element down slightly from its parent.
filter: blur(0.4rem) will blur the pseudo-element to create the appearance of a shadow underneath.
opacity: 0.7 makes the pseudo-element partially transparent.
z-index: -1 positions the pseudo-element behind the parent.

Browser support

⚠️ Requires prefixes for full support.

https://caniuse.com/#feat=css-filters

Etched text

Creates an effect where text appears to be "etched" or engraved into the background.

HTML

<p class="etched-text">I appear etched into the background.</p>

CSS

.etched-text {
  text-shadow: 0 2px white;
  font-size: 1.5rem;
  font-weight: bold;
  color: #b8bec5;
}

Demo

I appear etched into the background.

Explanation

text-shadow: 0 2px white creates a white shadow offset 0px horizontally and 2px vertically from the origin position.

The background must be darker than the shadow for the effect to work.

The text color should be slightly faded to make it look like it's engraved/carved out of the background.

Browser support

✅ No caveats.

https://caniuse.com/#feat=css-textshadow

Gradient text

Gives text a gradient color.

HTML

<p class="gradient-text">Gradient text</p>

CSS

.gradient-text {
  background: -webkit-linear-gradient(pink, red);
  -webkit-text-fill-color: transparent;
  -webkit-background-clip: text;
}

Demo

Gradient text

Explanation

background: -webkit-linear-gradient(...) gives the text element a gradient background.
webkit-text-fill-color: transparent fills the text with a transparent color.
webkit-background-clip: text clips the background with the text, filling the text with the gradient background as the color.

Browser support

⚠️ Uses non-standard properties.

https://caniuse.com/#feat=text-stroke

Hairline border

Gives an element a border equal to 1 native device pixel in width, which can look very sharp and crisp.

HTML

<div class="hairline-border">text</div>

CSS

.hairline-border {
  box-shadow: 0 0 0 1px;
}

@media (min-resolution: 2dppx) {
  .hairline-border {
    box-shadow: 0 0 0 0.5px;
  }
}

@media (min-resolution: 3dppx) {
  .hairline-border {
    box-shadow: 0 0 0 0.33333333px;
  }
}

@media (min-resolution: 4dppx) {
  .hairline-border {
    box-shadow: 0 0 0 0.25px;
  }
}

Demo

Text with a hairline border around it.

Explanation

box-shadow, when only using spread, adds a pseudo-border which can use subpixels*.
Use @media (min-resolution: ...) to check the device pixel ratio (1dppx equals 96 DPI), setting the spread of the box-shadow equal to 1 / dppx.

Browser Support

⚠️ Needs alternate syntax and JavaScript user agent checking for full support.

*Chrome does not support subpixel values on border. Safari does not support subpixel values on box-shadow. Firefox supports subpixel values on both.

Overflow scroll gradient

Adds a fading gradient to an overflowing element to better indicate there is more content to be scrolled.

HTML

<div class="overflow-scroll-gradient">
  <div class="overflow-scroll-gradient__scroller">
    Content to be scrolled
  </div>
</div>

CSS

.overflow-scroll-gradient {
  position: relative;
}
.overflow-scroll-gradient::after {
  content: '';
  position: absolute;
  bottom: 0;
  width: 240px;
  height: 25px;
  background: linear-gradient(
    rgba(255, 255, 255, 0.001),
    white
  ); /* transparent keyword is broken in Safari */
  pointer-events: none;
}
.overflow-scroll-gradient__scroller {
  overflow-y: scroll;
  background: white;
  width: 240px;
  height: 200px;
  padding: 15px 0;
  line-height: 1.2;
  text-align: center;
}

Demo

Content to be scrolled

Explanation

position: relative on the parent establishes a Cartesian positioning context for pseudo-elements.
::after defines a pseudo element.
background-image: linear-gradient(...) adds a linear gradient that fades from transparent to white (top to bottom).
position: absolute takes the pseudo element out of the flow of the document and positions it in relation to the parent.
width: 240px matches the size of the scrolling element (which is a child of the parent that has the pseudo element).
height: 25px is the height of the fading gradient pseudo-element, which should be kept relatively small.
bottom: 0 positions the pseudo-element at the bottom of the parent.
pointer-events: none specifies that the pseudo-element cannot be a target of mouse events, allowing text behind it to still be selectable/interactive.

Browser support

✅ No caveats.

https://caniuse.com/#feat=css-gradients

Pretty text underline

A nicer alternative to text-decoration: underline where descenders do not clip the underline. Natively implemented as text-decoration-skip-ink: auto but it has less control over the underline.

HTML

<p class="pretty-text-underline">Pretty text underline without clipping descending letters.</p>

CSS

.pretty-text-underline {
  font-family: Arial, sans-serif;
  display: inline;
  font-size: 18px;
  text-shadow: 1px 1px 0 #f5f6f9, -1px 1px 0 #f5f6f9, -1px -1px 0 #f5f6f9, 1px -1px 0 #f5f6f9;
  background-image: linear-gradient(90deg, currentColor 100%, transparent 100%);
  background-position: 0 0.98em;
  background-repeat: repeat-x;
  background-size: 1px 1px;
}
.pretty-text-underline::-moz-selection {
  background-color: rgba(0, 150, 255, 0.3);
  text-shadow: none;
}
.pretty-text-underline::selection {
  background-color: rgba(0, 150, 255, 0.3);
  text-shadow: none;
}

Demo

Pretty text underline without clipping descending letters.

Explanation

text-shadow: ... has 4 values with offsets that cover a 4x4 px area to ensure the underline has a "thick" shadow that covers the line where descenders clip it. Use a color that matches the background. For a larger font, use a larger px size.
background-image: linear-gradient(...) creates a 90deg gradient with the current text color (currentColor).
The background-* properties size the gradient as 1x1px at the bottom and repeats it along the x-axis.
The ::selection pseudo selector ensures the text shadow does not interfere with text selection.

Browser support

⚠️ The distance of the underline from the text depends on the internal metrics of a font, so you must ensure everyone sees the same font (i.e. no system fonts which will change based on the OS).

Reset all styles

Resets all styles to default values with one property. This will not affect direction and unicode-bidi properties.

HTML

<div class="reset-all-styles">
  <h4>Title</h4>
  <p>Lorem ipsum dolor sit amet consectetur adipisicing elit. Iure id exercitationem nulla qui repellat laborum vitae, molestias tempora velit natus. Quas, assumenda nisi. Quisquam enim qui iure, consequatur velit sit?</p>
</div>

CSS

.reset-all-styles {
  all: initial;
}

Demo

Title

Explanation

The all property allows you to reset all styles (inherited or not) to default values.

Browser support

⚠️ MS Edge status is under consideration.

https://caniuse.com/#feat=css-all

Shape separator

Uses an SVG shape to separate two different blocks to create more a interesting visual appearance compared to standard horizontal separation.

HTML

<div class="shape-separator"></div>

CSS

.shape-separator {
  position: relative;
  height: 48px;
  background: #333;
}
.shape-separator::after {
  content: '';
  background-image: url(data:image/svg+xml;base64,PHN2ZyB2aWV3Qm94PSIwIDAgMjQgMjQiIHhtbG5zPSJodHRwOi8vd3d3LnczLm9yZy8yMDAwL3N2ZyIgZmlsbC1ydWxlPSJldmVub2RkIiBjbGlwLXJ1bGU9ImV2ZW5vZGQiIHN0cm9rZS1saW5lam9pbj0icm91bmQiIHN0cm9rZS1taXRlcmxpbWl0PSIxLjQxNCI+PHBhdGggZD0iTTEyIDEybDEyIDEySDBsMTItMTJ6IiBmaWxsPSIjZmZmIi8+PC9zdmc+);
  position: absolute;
  width: 100%;
  height: 24px;
  bottom: 0;
}

Demo

Explanation

position: relative on the element establishes a Cartesian positioning context for pseudo elements.
::after defines a pseudo element.
background-image: url(...) adds the SVG shape (a 24x24 triangle in base64 format) as the background image of the pseudo element, which repeats by default. It must be the same color as the block that is being separated.
position: absolute takes the pseudo element out of the flow of the document and positions it in relation to the parent.
width: 100% ensures the element stretches the entire width of its parent.
height: 24px is the same height as the shape.
bottom: 0 positions the pseudo element at the bottom of the parent.

Browser support

✅ No caveats.

https://caniuse.com/#feat=svg

System font stack

Uses the native font of the operating system to get close to a native app feel.

HTML

<p class="system-font-stack">This text uses the system font.</p>

CSS

.system-font-stack {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen-Sans, Ubuntu,
    Cantarell, 'Helvetica Neue', Helvetica, Arial, sans-serif;
}

Demo

This text uses the system font.

Explanation

The browser looks for each successive font, preferring the first one if possible, and falls back to the next if it cannot find the font (on the system or defined in CSS).

-apple-system is San Francisco, used on iOS and macOS (not Chrome however)
BlinkMacSystemFont is San Francisco, used on macOS Chrome
Segoe UI is used on Windows 10
Roboto is used on Android
Oxygen-Sans is used on GNU+Linux
Ubuntu is used on Linux
"Helvetica Neue" and Helvetica is used on macOS 10.10 and below (wrapped in quotes because it has a space)
Arial is a font widely supported by all operating systems
sans-serif is the fallback sans-serif font if none of the other fonts are supported

Browser support

✅ No caveats.

Triangle

Creates a triangle shape with pure CSS.

HTML

<div class="triangle"></div>

CSS

.triangle {
  width: 0;
  height: 0;
  border-top: 20px solid #333;
  border-left: 20px solid transparent;
  border-right: 20px solid transparent;
}

Demo

Explanation

View this link for a detailed explanation.

The color of the border is the color of the triangle. The side the triangle tip points corresponds to the opposite border-* property. For example, a color on border-top means the arrow points downward.

Experiment with the px values to change the proportion of the triangle.

Browser support

✅ No caveats.

Bouncing loader

Creates a bouncing loader animation.

HTML

<div class="bouncing-loader">
  <div></div>
  <div></div>
  <div></div>
</div>

CSS

@keyframes bouncing-loader {
  from {
    opacity: 1;
    transform: translateY(0);
  }
  to {
    opacity: 0.1;
    transform: translateY(-1rem);
  }
}
.bouncing-loader {
  display: flex;
  justify-content: center;
}
.bouncing-loader > div {
  width: 1rem;
  height: 1rem;
  margin: 3rem 0.2rem;
  background: #8385aa;
  border-radius: 50%;
  animation: bouncing-loader 0.6s infinite alternate;
}
.bouncing-loader > div:nth-child(2) {
  animation-delay: 0.2s;
}
.bouncing-loader > div:nth-child(3) {
  animation-delay: 0.4s;
}

Demo

Explanation

Note: 1rem is usually 16px.

@keyframes defines an animation that has two states, where the element changes opacity and is translated up on the 2D plane using transform: translateY().
.bouncing-loader is the parent container of the bouncing circles and uses display: flex and justify-content: center to position them in the center.
.bouncing-loader > div, targets the three child divs of the parent to be styled. The divs are given a width and height of 1rem, using border-radius: 50% to turn them from squares to circles.
margin: 3rem 0.2rem specifies that each circle has a top/bottom margin of 3rem and left/right margin of 0.2rem so that they do not directly touch each other, giving them some breathing room.
animation is a shorthand property for the various animation properties: animation-name, animation-duration, animation-iteration-count, animation-direction are used.
nth-child(n) targets the element which is the nth child of its parent.
animation-delay is used on the second and third div respectively, so that each element does not start the animation at the same time.

Browser support

✅ No caveats.

https://caniuse.com/#feat=css-animation

Donut spinner

Creates a donut spinner that can be used to indicate the loading of content.

HTML

<div class="donut"></div>

CSS

@keyframes donut-spin {
  0% {
    transform: rotate(0deg);
  }
  100% {
    transform: rotate(360deg);
  }
}
.donut {
  display: inline-block;
  border: 4px solid rgba(0, 0, 0, 0.1);
  border-left-color: #7983ff;
  border-radius: 50%;
  width: 30px;
  height: 30px;
  animation: donut-spin 1.2s linear infinite;
}

Demo

Explanation

Use a semi-transparent border for the whole element, except one side that will serve as the loading indicator for the donut. Use animation to rotate the element.

Browser support

⚠️ Requires prefixes for full support.

Easing variables

Variables that can be reused for transition-timing-function properties, more powerful than the built-in ease, ease-in, ease-out and ease-in-out.

HTML

<div class="easing-variables"></div>

CSS

:root {
  --ease-in-quad: cubic-bezier(0.55, 0.085, 0.68, 0.53);
  --ease-in-cubic: cubic-bezier(0.55, 0.055, 0.675, 0.19);
  --ease-in-quart: cubic-bezier(0.895, 0.03, 0.685, 0.22);
  --ease-in-quint: cubic-bezier(0.755, 0.05, 0.855, 0.06);
  --ease-in-expo: cubic-bezier(0.95, 0.05, 0.795, 0.035);
  --ease-in-circ: cubic-bezier(0.6, 0.04, 0.98, 0.335);

  --ease-out-quad: cubic-bezier(0.25, 0.46, 0.45, 0.94);
  --ease-out-cubic: cubic-bezier(0.215, 0.61, 0.355, 1);
  --ease-out-quart: cubic-bezier(0.165, 0.84, 0.44, 1);
  --ease-out-quint: cubic-bezier(0.23, 1, 0.32, 1);
  --ease-out-expo: cubic-bezier(0.19, 1, 0.22, 1);
  --ease-out-circ: cubic-bezier(0.075, 0.82, 0.165, 1);

  --ease-in-out-quad: cubic-bezier(0.455, 0.03, 0.515, 0.955);
  --ease-in-out-cubic: cubic-bezier(0.645, 0.045, 0.355, 1);
  --ease-in-out-quart: cubic-bezier(0.77, 0, 0.175, 1);
  --ease-in-out-quint: cubic-bezier(0.86, 0, 0.07, 1);
  --ease-in-out-expo: cubic-bezier(1, 0, 0, 1);
  --ease-in-out-circ: cubic-bezier(0.785, 0.135, 0.15, 0.86);
}

.easing-variables {
  width: 50px;
  height: 50px;
  background: #333;
  transition: transform 1s var(--ease-out-quart);
}

.easing-variables:hover {
  transform: rotate(45deg);
}

Demo

Hover

Explanation

The variables are defined globally within the :root CSS pseudo-class which matches the root element of a tree representing the document. In HTML, :root represents the <html> element and is identical to the selector html, except that its specificity is higher.

Browser support

✅ No caveats.

https://caniuse.com/#feat=css-variables

Hover underline animation

Creates an animated underline effect when the text is hovered over.

Credit: https://flatuicolors.com/

HTML

<p class="hover-underline-animation">Hover this text to see the effect!</p>

CSS

.hover-underline-animation {
  display: inline-block;
  position: relative;
  color: #0087ca;
}
.hover-underline-animation::after {
  content: '';
  position: absolute;
  width: 100%;
  transform: scaleX(0);
  height: 2px;
  bottom: 0;
  left: 0;
  background-color: #0087ca;
  transform-origin: bottom right;
  transition: transform 0.25s ease-out;
}
.hover-underline-animation:hover::after {
  transform: scaleX(1);
  transform-origin: bottom left;
}

Demo

Hover this text to see the effect!

Explanation

display: inline-block makes the block p an inline-block to prevent the underline from spanning the entire parent width rather than just the content (text).
position: relative on the element establishes a Cartesian positioning context for pseudo-elements.
::after defines a pseudo-element.
position: absolute takes the pseudo element out of the flow of the document and positions it in relation to the parent.
width: 100% ensures the pseudo-element spans the entire width of the text block.
transform: scaleX(0) initially scales the pseudo element to 0 so it has no width and is not visible.
bottom: 0 and left: 0 position it to the bottom left of the block.
transition: transform 0.25s ease-out means changes to transform will be transitioned over 0.25 seconds with an ease-out timing function.
transform-origin: bottom right means the transform anchor point is positioned at the bottom right of the block.
:hover::after then uses scaleX(1) to transition the width to 100%, then changes the transform-origin to bottom left so that the anchor point is reversed, allowing it transition out in the other direction when hovered off.

Browser support

✅ No caveats.

Disable selection

Makes the content unselectable.

HTML

<p>You can select me.</p>
<p class="unselectable">You can't select me!</p>

CSS

.unselectable {
  user-select: none;
}

Demo

You can select me.

You can't select me!

Explanation

user-select: none specifies that the text cannot be selected.

Browser support

⚠️ Requires prefixes for full support. ⚠️ This is not a secure method to prevent users from copying content.

https://caniuse.com/#feat=user-select-none

Mouse cursor gradient tracking

A hover effect where the gradient follows the mouse cursor.

Credit: Tobias Reich

HTML

<button class="mouse-cursor-gradient-tracking">
  <span>Hover me</span>
</button>

CSS

.mouse-cursor-gradient-tracking {
  position: relative;
  background: #7983ff;
  padding: 0.5rem 1rem;
  font-size: 1.2rem;
  border: none;
  color: white;
  cursor: pointer;
  outline: none;
  overflow: hidden;
}

.mouse-cursor-gradient-tracking span {
  position: relative;
}

.mouse-cursor-gradient-tracking::before {
  --size: 0;
  content: '';
  position: absolute;
  left: var(--x);
  top: var(--y);
  width: var(--size);
  height: var(--size);
  background: radial-gradient(circle closest-side, pink, transparent);
  transform: translate(-50%, -50%);
  transition: width 0.2s ease, height 0.2s ease;
}

.mouse-cursor-gradient-tracking:hover::before {
  --size: 200px;
}

JavaScript

var btn = document.querySelector('.mouse-cursor-gradient-tracking')
btn.onmousemove = function(e) {
  var x = e.pageX - btn.offsetLeft
  var y = e.pageY - btn.offsetTop
  btn.style.setProperty('--x', x + 'px')
  btn.style.setProperty('--y', y + 'px')
}

Demo

Hover me

Explanation

TODO

Note!

If the element's parent has a positioning context (position: relative), you will need to subtract its offsets as well.

var x = e.pageX - btn.offsetLeft - btn.offsetParent.offsetLeft
var y = e.pageY - btn.offsetTop - btn.offsetParent.offsetTop

Browser support

Requires JavaScript

⚠️ Requires JavaScript.

https://caniuse.com/#feat=css-variables

Popout menu

Reveals an interactive popout menu on hover.

HTML

<div class="reference">
  <div class="popout-menu">
    Popout menu
  </div>
</div>

CSS

.reference {
  position: relative;
}
.popout-menu {
  position: absolute;
  visibility: hidden;
  left: 100%;
}
.reference:hover > .popout-menu {
  visibility: visible;
}

Demo

Popout menu

Explanation

position: relative on the reference parent establishes a Cartesian positioning context for its child.
position: absolute takes the popout menu out of the flow of the document and positions it in relation to the parent.
left: 100% moves the the popout menu 100% of its parent's width from the left.
visibility: hidden hides the popout menu initially and allows for transitions (unlike display: none).
.reference:hover > .popout-menu means that when .reference is hovered over, select immediate children with a class of .popout-menu and change their visibility to visible, which shows the popout.

Browser support

✅ No caveats.

Sibling fade

Fades out the siblings of a hovered item.

HTML

<div class="sibling-fade">
  <span>Item 1</span>
  <span>Item 2</span>
  <span>Item 3</span>
  <span>Item 4</span>
  <span>Item 5</span>
  <span>Item 6</span>
</div>

CSS

span {
  padding: 0 1rem;
  transition: opacity 0.2s;
}

.sibling-fade:hover span:not(:hover) {
  opacity: 0.5;
}

Demo

Item 1 Item 2 Item 3 Item 4 Item 5 Item 6

Explanation

transition: opacity 0.2s specifies that changes to opacity will be transitioned over 0.2 seconds.
.sibling-fade:hover span:not(:hover) specifies that when the parent is hovered, select any span children that are not currently being hovered and change their opacity to 0.5.

Browser support

✅ No caveats.

Custom variables

CSS variables that contain specific values to be reused throughout a document.

HTML

<p class="custom-variables">CSS is awesome!</p>

CSS

:root {
  --some-color: #da7800;
  --some-keyword: italic;
  --some-size: 1.25em;
  --some-complex-value: 1px 1px 2px whitesmoke, 0 0 1em slategray, 0 0 0.2em slategray;
}

.custom-variables {
  color: var(--some-color);
  font-size: var(--some-size);
  font-style: var(--some-keyword);
  text-shadow: var(--some-complex-value);
}

Demo

CSS is awesome!

Explanation

The variables are defined globally within the :root CSS pseudo-class which matches the root element of a tree representing the document. Variables can also be scoped to a selector if defined within the block.

Declare a variable with --variable-name:.

Reuse variables throughout the document using the var(--variable-name) function.

Browser support

✅ No caveats.

https://caniuse.com/#feat=css-variables