GPT-4 Inspired Lines Animation In Pure CSS

A CSS solution to create an infinite horizontal lines animation as you’ve seen on GPT-4 website.

How to use it:

1. Add lines to the page.

<div class="lines">
  <div class="row">
    <div class="track">
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
    </div>
  </div>
  <div class="row">
    <div class="track">
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
    </div>
  </div>
  <div class="row">
    <div class="track">
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
    </div>
  </div>
  <div class="row">
    <div class="track">
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
    </div>
  </div>
  <div class="row">
    <div class="track">
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
    </div>
  </div>
  <div class="row">
    <div class="track">
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
      <div class="line"></div>
    </div>
  </div>
</div>

2. Add the following CSS snippets to the page. Done.

@property --d-c {
  syntax: "<number>";
  inherits: false;
  initial-value: 1;
}
body {
  background: black;
  display: grid;
  place-items: center;
  align-content: center;
  min-height: 100vh;
  font-size: max(20px, 10vw);
  overflow: hidden;
  box-sizing: border-box;
}
.lines {
  display: grid;
  gap: 50px;
  -webkit-box-reflect: bottom;
}
.row {
  position: relative;
  width: 100%;
}
.track {
  display: flex;
  white-space: nowrap;
  transition: 1s;
  -webkit-animation: slide calc(var(--d) * var(--d-c, 1)) linear infinite;
          animation: slide calc(var(--d) * var(--d-c, 1)) linear infinite;
}
@-webkit-keyframes slide {
  from {
    translate: var(--from) 0;
  }
  to {
    translate: var(--to) 0;
  }
}
@keyframes slide {
  from {
    translate: var(--from) 0;
  }
  to {
    translate: var(--to) 0;
  }
}
.line {
  display: inline-block;
  height: 10px;
  background: var(--bg);
  flex: 1 0 auto;
  width: calc(1em * var(--w));
  margin-right: clamp(30px, 0.5em, 60px);
}
.row:nth-child(1) {
  --d: 12.5s;
}
.row:nth-child(1):nth-child(odd) {
  --from: -50%;
  --to: 0%;
}
.row:nth-child(1):nth-child(even) {
  --to: -50%;
}
.row:nth-child(1) .line:nth-child(7n+1) {
  --bg: #51da4c;
  --w: 3;
}
.row:nth-child(1) .line:nth-child(7n+2) {
  --bg: #fff;
  --w: 4;
}
.row:nth-child(1) .line:nth-child(7n+3) {
  --bg: #51da4c;
  --w: 3;
}
.row:nth-child(1) .line:nth-child(7n+4) {
  --bg: #fff;
  --w: 4;
}
.row:nth-child(1) .line:nth-child(7n+5) {
  --bg: #51da4c;
  --w: 3;
}
.row:nth-child(1) .line:nth-child(7n+6) {
  --bg: #fff;
  --w: 3;
}
.row:nth-child(1) .line:nth-child(7n+7) {
  --bg: #fff;
  --w: 2;
}
.row:nth-child(2) {
  --d: 15s;
}
.row:nth-child(2):nth-child(odd) {
  --from: -50%;
  --to: 0%;
}
.row:nth-child(2):nth-child(even) {
  --to: -50%;
}
.row:nth-child(2) .line:nth-child(7n+1) {
  --bg: #51da4c;
  --w: 4;
}
.row:nth-child(2) .line:nth-child(7n+2) {
  --bg: #51da4c;
  --w: 3;
}
.row:nth-child(2) .line:nth-child(7n+3) {
  --bg: #fff;
  --w: 3;
}
.row:nth-child(2) .line:nth-child(7n+4) {
  --bg: #51da4c;
  --w: 2;
}
.row:nth-child(2) .line:nth-child(7n+5) {
  --bg: #fff;
  --w: 3;
}
.row:nth-child(2) .line:nth-child(7n+6) {
  --bg: #fff;
  --w: 3;
}
.row:nth-child(2) .line:nth-child(7n+7) {
  --bg: #fff;
  --w: 4;
}
.row:nth-child(3) {
  --d: 15s;
}
.row:nth-child(3):nth-child(odd) {
  --from: -50%;
  --to: 0%;
}
.row:nth-child(3):nth-child(even) {
  --to: -50%;
}
.row:nth-child(3) .line:nth-child(7n+1) {
  --bg: #fff;
  --w: 3;
}
.row:nth-child(3) .line:nth-child(7n+2) {
  --bg: #fff;
  --w: 4;
}
.row:nth-child(3) .line:nth-child(7n+3) {
  --bg: #fff;
  --w: 4;
}
.row:nth-child(3) .line:nth-child(7n+4) {
  --bg: #fff;
  --w: 1;
}
.row:nth-child(3) .line:nth-child(7n+5) {
  --bg: #fff;
  --w: 2;
}
.row:nth-child(3) .line:nth-child(7n+6) {
  --bg: #51da4c;
  --w: 3;
}
.row:nth-child(3) .line:nth-child(7n+7) {
  --bg: #51da4c;
  --w: 3;
}
.row:nth-child(4) {
  --d: 12.5s;
}
.row:nth-child(4):nth-child(odd) {
  --from: -50%;
  --to: 0%;
}
.row:nth-child(4):nth-child(even) {
  --to: -50%;
}
.row:nth-child(4) .line:nth-child(7n+1) {
  --bg: #51da4c;
  --w: 4;
}
.row:nth-child(4) .line:nth-child(7n+2) {
  --bg: #51da4c;
  --w: 3;
}
.row:nth-child(4) .line:nth-child(7n+3) {
  --bg: #fff;
  --w: 1;
}
.row:nth-child(4) .line:nth-child(7n+4) {
  --bg: #fff;
  --w: 4;
}
.row:nth-child(4) .line:nth-child(7n+5) {
  --bg: #51da4c;
  --w: 3;
}
.row:nth-child(4) .line:nth-child(7n+6) {
  --bg: #51da4c;
  --w: 4;
}
.row:nth-child(4) .line:nth-child(7n+7) {
  --bg: #fff;
  --w: 4;
}
.row:nth-child(5) {
  --d: 15s;
}
.row:nth-child(5):nth-child(odd) {
  --from: -50%;
  --to: 0%;
}
.row:nth-child(5):nth-child(even) {
  --to: -50%;
}
.row:nth-child(5) .line:nth-child(7n+1) {
  --bg: #51da4c;
  --w: 4;
}
.row:nth-child(5) .line:nth-child(7n+2) {
  --bg: #51da4c;
  --w: 1;
}
.row:nth-child(5) .line:nth-child(7n+3) {
  --bg: #51da4c;
  --w: 4;
}
.row:nth-child(5) .line:nth-child(7n+4) {
  --bg: #fff;
  --w: 1;
}
.row:nth-child(5) .line:nth-child(7n+5) {
  --bg: #51da4c;
  --w: 1;
}
.row:nth-child(5) .line:nth-child(7n+6) {
  --bg: #51da4c;
  --w: 2;
}
.row:nth-child(5) .line:nth-child(7n+7) {
  --bg: #51da4c;
  --w: 3;
}
.row:nth-child(6) {
  --d: 10s;
}
.row:nth-child(6):nth-child(odd) {
  --from: -50%;
  --to: 0%;
}
.row:nth-child(6):nth-child(even) {
  --to: -50%;
}
.row:nth-child(6) .line:nth-child(7n+1) {
  --bg: #51da4c;
  --w: 4;
}
.row:nth-child(6) .line:nth-child(7n+2) {
  --bg: #fff;
  --w: 3;
}
.row:nth-child(6) .line:nth-child(7n+3) {
  --bg: #51da4c;
  --w: 1;
}
.row:nth-child(6) .line:nth-child(7n+4) {
  --bg: #fff;
  --w: 4;
}
.row:nth-child(6) .line:nth-child(7n+5) {
  --bg: #fff;
  --w: 1;
}
.row:nth-child(6) .line:nth-child(7n+6) {
  --bg: #fff;
  --w: 3;
}
.row:nth-child(6) .line:nth-child(7n+7) {
  --bg: #fff;
  --w: 3;
}