discourse/plugins/chat/assets/stylesheets/common/chat-replying-indicator.scss

.chat-replying-indicator {
  color: var(--primary-medium);
  display: inline-flex;
  font-size: var(--font-down-2);

  &-container {
    display: flex;
    height: 16px;
  }

  &:before {
    // unicode zero width space character
    // Ensures the span height is consistent even when empty
    content: "\200b";
  }

  .chat-replying-indicator__text {
    display: inline-flex;
  }

  .chat-replying-indicator__wave {
    flex: 0 0 auto;
    display: inline-flex;

    .chat-replying-indicator__dot {
      display: inline-block;
      @media (prefers-reduced-motion: no-preference) {
        animation: chat-replying-indicator__wave 1.8s linear infinite;
      }
      &:nth-child(2) {
        animation-delay: -1.6s;
      }
      &:nth-child(3) {
        animation-delay: -1.4s;
      }
    }

    @keyframes chat-replying-indicator__wave {
      0%,
      60%,
      100% {
        transform: initial;
      }
      30% {
        transform: translateY(-0.2em);
      }
    }
  }
}