@difizen/magent-chat/src/chat-view/components/typing/index.less

.chat-input-typing {
  @keyframes blink {
    0% {
      opacity: 1;
    }

    50% {
      opacity: 0;
    }

    100% {
      opacity: 1;
    }
  }

  height: 14px;
  display: inline-block;
  border-left: 4px solid var(--mana-text-color);
  animation: blink 0.8s infinite;
  vertical-align: baseline;
}