30秒学会 CSS 片段 – Pulse loader

Creates a pulse effect loader animation using the animation-delay property.

• Use @keyframes to define an animation at two points in the cycle, start (0%), where the two <div> elements have no width or height and are positioned at the center and end (100%), where both <div> elements have increased width and height, but their position is reset to 0.
• Use opacity to transition from 1 to 0 when animating to give the <div> elements a disappearing effect as they expand.
• .ripple-loader, which is the parent container, has a predefined width and height. It uses position: relative to position its children.
• Use animation-delay on the second <div> element, so that each element starts its animation at a different time.

预览

HTML

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

CSS

.ripple-loader {
  position: relative;
  width: 64px;
  height: 64px;
}

.ripple-loader div {
  position: absolute;
  border: 4px solid #454ADE;
  border-radius: 50%;
  animation: ripple-loader 1s ease-out infinite;
}

.ripple-loader div:nth-child(2) {
  animation-delay: -0.5s;
}

@keyframes ripple-loader {
  0% {
    top: 32px;
    left: 32px;
    width: 0;
    height: 0;
    opacity: 1;
  }
  100% {
    top: 0;
    left: 0;
    width: 64px;
    height: 64px;
    opacity: 0;
  }
}

翻译自：https://www.30secondsofcode.org/css/s/pulse-loader