searxng/searx/static/themes/simple/src/less/animations.less

.dialog-modal {
  animation-name: dialogmodal;
  animation-duration: 0.13s;

  @keyframes dialogmodal {
    0% {
      opacity: 0;
    }

    50% {
      opacity: 0.5;
      transform: translate(-50%, -50%) scale(1.05);
    }
  }
}