Pen Settings

HTML

CSS

CSS Base

Vendor Prefixing

Add External Stylesheets/Pens

Any URLs added here will be added as <link>s in order, and before the CSS in the editor. You can use the CSS from another Pen by using its URL and the proper URL extension.

+ add another resource

JavaScript

Babel includes JSX processing.

Add External Scripts/Pens

Any URL's added here will be added as <script>s in order, and run before the JavaScript in the editor. You can use the URL of any other Pen and it will include the JavaScript from that Pen.

+ add another resource

Packages

Add Packages

Search for and use JavaScript packages from npm here. By selecting a package, an import statement will be added to the top of the JavaScript editor for this package.

Behavior

Auto Save

If active, Pens will autosave every 30 seconds after being saved once.

Auto-Updating Preview

If enabled, the preview panel updates automatically as you code. If disabled, use the "Run" button to update.

Format on Save

If enabled, your code will be formatted when you actively save your Pen. Note: your code becomes un-folded during formatting.

Editor Settings

Code Indentation

Want to change your Syntax Highlighting theme, Fonts and more?

Visit your global Editor Settings.

HTML

              
                <div class="container">
  <div class="entry">
    <div class="entry-content">1</div>
    <div class="corner-container">
      <span class="corner"></span>
      <span class="corner"></span>
      <span class="corner"></span>
      <span class="corner"></span>
    </div>
  </div>
   <div class="entry">
    <div class="entry-content">2</div>
    <div class="corner-container">
      <span class="corner"></span>
      <span class="corner"></span>
      <span class="corner"></span>
      <span class="corner"></span>
    </div>
  </div>
  <div class="entry">
    <div class="entry-content">3</div>
    <div class="corner-container">
      <span class="corner"></span>
      <span class="corner"></span>
      <span class="corner"></span>
      <span class="corner"></span>
    </div>
  </div>
  <div class="entry">
    <div class="entry-content">4</div>
    <div class="corner-container">
      <span class="corner"></span>
      <span class="corner"></span>
      <span class="corner"></span>
      <span class="corner"></span>
    </div>
  </div>
  <div class="entry">
    <div class="entry-content">5</div>
    <div class="corner-container">
      <span class="corner"></span>
      <span class="corner"></span>
      <span class="corner"></span>
      <span class="corner"></span>
    </div>
  </div>
  <div class="entry">
    <div class="entry-content">6</div>
    <div class="corner-container">
      <span class="corner"></span>
      <span class="corner"></span>
      <span class="corner"></span>
      <span class="corner"></span>
    </div>
  </div>
  <div class="entry">
    <div class="entry-content">7</div>
    <div class="corner-container">
      <span class="corner"></span>
      <span class="corner"></span>
      <span class="corner"></span>
      <span class="corner"></span>
    </div>
  </div>
  <div class="entry">
    <div class="entry-content">8</div>
    <div class="corner-container">
      <span class="corner"></span>
      <span class="corner"></span>
      <span class="corner"></span>
      <span class="corner"></span>
    </div>
  </div>
  <div class="entry">
    <div class="entry-content">9</div>
    <div class="corner-container">
      <span class="corner"></span>
      <span class="corner"></span>
      <span class="corner"></span>
      <span class="corner"></span>
    </div>
  </div>
</div>

<p class="warning">Inspired from a Windows 10 Fluent Design effect on the Calculator App, where hovering over an item shows a subtle cross in the corner closest to the cursor. <a class="more" target="_blank" href="https://www.gsarigiannidis.gr/windows-fluent-design-css-cross-hover-corner/">Read more</a></p>
              
            
!

CSS

              
                :root {
  --gap: 4px;
  --background-page: #111;
  --background-container: #333;
  --background-box: #222;
  --color-line: #666;
  --color-font: #444;
  --columns: 3;
  --border-radius: 3px;
  --font-size: 18px;
  --font-family: Arial;
  --transition-duration: 600ms;
  --transition-style: ease-in-out;
  --container-max-width: 640px;
}
body {
  background: var(--background-page);
  font-family: var(--font-family);
  font-size: var(--font-size);
  color: var(--color-font);
}
p.warning {
  text-align: center;
  line-height: 2;
  margin: 0 auto;
  font-size: 14px;
  max-width: var(--container-max-width);
  color: #fff;
}
p.warning a {
    background: #45ba04;
    color: #fff;
    padding: .2rem .7rem;
    border-radius: 3px;
    white-space: nowrap;
    text-decoration: none;
}
p.warning a.more:hover {
      background: #3bacff;
}
.container {
  background: var(--background-container);
  box-shadow: 0 0 16px rgba(0,0,0,1);
  border-radius: var(--border-radius);
  margin: 2em auto;
  max-width: var(--container-max-width);
  display: flex;
  flex-flow: wrap;
  justify-content: space-between; /* Horizontal spacing between the entries. */
  padding: var(--gap) var(--gap) calc(var(--gap)/2) var(--gap); /* The external spacing of the container. */
  overflow: hidden; /* Prevents .corner::before to be visible outside the margins of the container. */
}
.entry {
  width: calc((100% / var(--columns)) - calc(var(--gap)/2)); /* Column width must take into account the desired gap. */
  margin-bottom: calc(var(--gap)/2); /* Vertical spacing between the entries. */
  position: relative; /* This is required, to contain .corner::before within the margins of it's parent. */
}
.entry-content {
  display: grid;
  place-items: center;
  min-height: clamp( 1em, calc(100vw/var(--columns)), calc(var(--container-max-width)/var(--columns)) );
  background: var(--background-box);
  transition: all var(--transition-duration) var(--transition-style);
  pointer-events: none; /* When hovering over an entry, ignore this element, even if its on the foreground. */
  z-index: 1; /* The content div should have a higher z-index than the .corner::before. */ 
  position: relative; /* z-index would have no effect without a specific position. */
}
.entry:hover .entry-content {
  background: var(--background-container);
  color: var(--color-line);
}
.corner-container { /* The corner container should cover the entire entry. */
  width: 100%;
  height: 100%;
  top: 0;
  left: 0;
  position: absolute;
}
.corner { /* Each corner should cover 1/4 of an entry. */
  position: absolute;
  width: 50%;
  height: 50%;
}
.corner::before { /* The cross shape is just a big box positioned behind the entries. */
  content: '';
  display: block;
  position: absolute;
  width: 200%;
  height: 200%;
  opacity: 0;
  transition: opacity var(--transition-duration) var(--transition-style);
  background: radial-gradient(var(--color-line) 0, transparent 70%); /* Radial gradient smoothens the shape's edges. */
  pointer-events: none; /* This is needed to prevent hovering on the ::before element instead of its container span. */
}
.corner:hover::before {
  opacity: 1;
}
/* Position the corners and their respective shapes. */
.corner:nth-child(1) {
  left: 0;
  top: 0;
}
.corner:nth-child(1)::before {
  left: -100%;
  top: -100%;
}
.corner:nth-child(2) {
  right: 0;
  top: 0;
}
.corner:nth-child(2)::before {
  right: -100%;
  top: -100%;
}
.corner:nth-child(3) {
  left: 0;
  bottom: 0;
}
.corner:nth-child(3)::before {
  left: -100%;
  bottom: -100%;
}
.corner:nth-child(4) {
  right: 0;
  bottom: 0;
}
.corner:nth-child(4)::before {
  right: -100%;
  bottom: -100%;
}
              
            
!

JS

              
                
              
            
!
999px

Console