electronotes/app/renderer/common/css/materialize/components/_pulse.scss

.pulse {
  &::before {
    content: '';
    display: block;
    position: absolute;
    width: 100%;
    height: 100%;
    top: 0;
    left: 0;
    background-color: inherit;
    border-radius: inherit;
    transition: opacity .3s, transform .3s;
    animation: pulse-animation 1s cubic-bezier(0.24, 0, 0.38, 1) infinite;
    z-index: -1;
  }

  overflow: visible;
  position: relative;
}

@keyframes pulse-animation {
  0% {
    opacity: 1;
    transform: scale(1);
  }
  50% {
    opacity: 0;
    transform: scale(1.5);
  }
  100% {
    opacity: 0;
    transform: scale(1.5);
  }
}