pulse.css

@property --x {
  syntax: '<percentage>';
  inherits: false;
  initial-value: 0%;
}

@keyframes colorChange {
  0% {
    --x:0%;
  }
  50% {
    --x:50%;
  }
  100% {
    --x:100%;
  }
}

@keyframes pulse {
  from {
    background: radial-gradient(circle, rgba(51,153,51,1) 0%, rgba(0,0,0,1) 100%);
  }
  to {
    background: radial-gradient(circle, rgba(51,153,51,1) 100%, rgba(0,0,0,1) 100%);
  }
}

.CommandPalette > button.active {
  animation-duration: 0.5s;
  animation-name: colorChange;
  animation-timing-function: linear;
  animation-iteration-count: infinite;

  background: radial-gradient(circle, rgba(51,153,51,1) var(--x), rgba(0,0,0,1) 200%);
}