Cursor aware border

Borders that look great when you hover over the content.

by jshacker

HTML

<div id="cards">
  <div class="card">
    <div class="card-content">
      <div class="card-image">
        <i class="fa-duotone fa-apartment"></i>
      </div>
      <div class="card-info-wrapper">
        <div class="card-info">
          <i class="fa-duotone fa-apartment"></i>
          <div class="card-info-title">
            <h3>Apartments</h3>
            <h4>Places to be apart. Wait, what?</h4>
          </div>
        </div>
      </div>
    </div>
  </div>
  <div class="card">
    <div class="card-content">
      <div class="card-image">
        <i class="fa-duotone fa-unicorn"></i>
      </div>
      <div class="card-info-wrapper">
        <div class="card-info">
          <i class="fa-duotone fa-unicorn"></i>
          <div class="card-info-title">
            <h3>Unicorns</h3>
            <h4>A single corn. Er, I mean horn.</h4>
          </div>
        </div>
      </div>
    </div>
  </div>
  <div class="card">
    <div class="card-content">
      <div class="card-image">
        <i class="fa-duotone fa-blender-phone"></i>
      </div>
      <div class="card-info-wrapper">
        <div class="card-info">
          <i class="fa-duotone fa-blender-phone"></i>
          <div class="card-info-title">
            <h3>Blender Phones</h3>
            <h4>These absolutely deserve to exist.</h4>
          </div>
        </div>
      </div>
    </div>
  </div>
  <div class="card">
    <div class="card-content">
      <div class="card-image">
        <i class="fa-duotone fa-person-to-portal"></i>
      </div>
      <div class="card-info-wrapper">
        <div class="card-info">
          <i class="fa-duotone fa-person-to-portal"></i>
          <div class="card-info-title">
            <h3>Adios</h3>
            <h4>See you...</h4>
          </div>
        </div>
      </div>
    </div>
  </div>
  <div class="card">
    <div class="card-content">
      <div class="card-image">
        <i...

CSS

:root {
  --bg-color: rgb(20, 20, 20);
  --card-color: rgb(23, 23, 23);
}

body {
  align-items: center;
  background-color: var(--bg-color);
  display: flex;
  height: 100vh;
  justify-content: center;
  margin: 0px;
  overflow: hidden;
  padding: 0px;
}

#cards {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  max-width: 916px;
  width: calc(100% - 20px);
}

#cards:hover > .card::after {
  opacity: 1;
}

.card {
  background-color: rgba(255, 255, 255, 0.1);
  border-radius: 10px;
  cursor: pointer;
  display: flex;
  height: 260px;
  flex-direction: column;
  position: relative;
  width: 300px;
}

.card:hover::before {
  opacity: 1;
}

.card::before,
.card::after {
  border-radius: inherit;
  content: "";
  height: 100%;
  left: 0px;
  opacity: 0;
  position: absolute;
  top: 0px;
  transition: opacity 500ms;
  width: 100%;
}

.card::before {
  background: radial-gradient(
    800px circle at var(--mouse-x) var(--mouse-y),
    rgba(255, 255, 255, 0.06),
    transparent 40%
  );
  z-index: 3;
}

.card::after {
  background: radial-gradient(
    600px circle at var(--mouse-x) var(--mouse-y),
    rgba(255, 255, 255, 0.4),
    transparent 40%
  );
  z-index: 1;
}

.card > .card-content {
  background-color: var(--card-color);
  border-radius: inherit;
  display: flex;
  flex-direction: column;
  flex-grow: 1;
  inset: 1px;
  padding: 10px;
  position: absolute;
  z-index: 2;
}

/* -- ↓ ↓ ↓ extra card content styles ↓ ↓ ↓ -- */

h1,
h2,
h3,
h4,
span {
  color: rgb(240, 240, 240);
  font-family: "Rubik", sans-serif;
  font-weight: 400;
  margin: 0px;
}

i {
  color: rgb(240, 240, 240);
}

.card-image {
  align-items: center;
  display: flex;
  height: 140px;
  justify-content: center;
  overflow: hidden;
}

.card-image > i {
  font-size: 6em;
  opacity: 0.25;
}

.card-info-wrapper {
  align-items: center;
  display: flex;
  flex-grow: 1;
 ...

JavaScript

document.getElementById("cards").onmousemove = (e) => {
  for (const card of document.getElementsByClassName("card")) {
    const rect = card.getBoundingClientRect(),
      x = e.clientX - rect.left,
      y = e.clientY - rect.top

    card.style.setProperty("--mouse-x", `${x}px`)
    card.style.setProperty("--mouse-y", `${y}px`)
  }
}