Richard Bustos Richard Bustos - 7 months ago 276
HTML Question

Pulsating ring animation with CSS

I want to have an expanding radius that starts from the center of the

div
instead of it starting on the top left of the
div
.

Imagine the button has a pulsing outline that goes outwards. That pulsing outline should start from the middle of the
div
and go out.

See example here: https://jsbin.com/dinehoqaro/edit?html,css,output

You can see that the expansion is starting from the top left.



.circle {
background-color: white;
border: 1px solid red;
border-radius: 50%;
width: 50px;
height: 50px;
animation: pulse 1s infinte;
-webkit-animation: pulse 1.2s infinite;
}
button {
background-color: green;
border: none;
border-radius: 50%;
width: 50px;
height: 50px;
}
@-webkit-keyframes pulse {
from {
width: 50px;
height: 50px;
}
to {
width: 100px height: 100px;
}
}
@keyframes pulse {
from {
width: 50px;
height: 50px;
}
to {
width: 100px;
height: 100px;
}
}

<div class="circle"><button>click here</button></div>




Answer

Here's a general solution using CSS flexbox, transform and pseudo-elements.

html {
  height: 100%;
}
body {
  display: flex;
  align-items: center;
  justify-content: center;
  background-color: lightyellow;
  min-height: 95%;
}
#container {
  display: flex;
  align-items: center;
  justify-content: center;
}
.sphere {
  display: flex;
  background: lightblue;
  border-radius: 300px;
  height: 100px;
  width: 100px;
}
#container::after {
  display: flex;
  background: lightpink;
  border-radius: 300px;
  height: 250px;
  width: 250px;
  animation: pulsate 2.5s ease-out;
  animation-iteration-count: infinite;
  opacity: 0.0;
  content: "";
  z-index: -1;
  margin: auto;
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
}
@keyframes pulsate {
  0% {
    transform: scale(0.1, 0.1);
    opacity: 0.0;
  }
  50% {
    opacity: 1.0;
  }
  100% {
    transform: scale(1.2, 1.2);
    opacity: 0.0;
  }
}
<div id="container">
  <div class="sphere"></div>
</div>

jsFiddle

Also see this awesome solution by @harry: How to create a pulsing glow ring animation in CSS?