zen-desktop/src/browser/base/content/zen-styles/zen-animations.css

@keyframes zen-jello-animation {
  0% {
    transform: scale3d(0.8, 0.8, 0.8);
  }

  60% {
    transform: scale3d(1.02, 1.02, 1.02);
  }

  to {
    opacity: 1;
    transform: scale3d(1, 1, 1);
  }
}

@keyframes zen-jello-out-animation {
  0% {
    transform: scale3d(1, 1, 1);
  }

  60% {
    transform: scale3d(1.02, 1.02, 1.02);
  }

  99% {
    opacity: 0;
    transform: scale3d(0.8, 0.8, 0.8);
  }

  100% {
    -moz-window-transform: none;
    transform: none;
  }
}

@keyframes zen-slide-in {
  from {
    transform: translateX(-10px);
    opacity: 0;
  }
  to {
    transform: translateX(0);
    opacity: 1;
  }
}

@keyframes zen-zoom-in {
  from {
    transform: scale(0.5);
    opacity: 0;
  }
  to {
    opacity: 1;
    transform: scale(1);
  }
}