discourse/plugins/chat/assets/stylesheets/common/chat-skeleton.scss

$radius: 10px;

.chat-skeleton {
  height: auto;

  &__body {
    padding: 0.5em 1em;
  }

  &__message {
    display: grid;
    grid-template:
      "avatar poster"
      "avatar content"
      ". content";
    grid-template-columns: auto 1fr;

    &:not(:first-of-type):not(:last-of-type) {
      margin-top: 1.5em;
      margin-bottom: 1.5em;
    }
  }

  &__message-avatar {
    grid-area: avatar;
    width: 30px;
    height: 30px;
    border-radius: 50%;
    margin-right: 0.5rem;

    .chat-skeleton__body:nth-of-type(odd) & {
      background-color: var(--primary-100);
    }
    .chat-skeleton__body:nth-of-type(even) & {
      background-color: var(--primary-200);
    }
  }

  &__message-poster {
    grid-area: poster;
    margin-top: 0.25rem;
    margin-bottom: 0.25rem;
    width: 70px;
    height: 20px;
    border-radius: $radius;

    .chat-skeleton__body:nth-of-type(odd) & {
      background-color: var(--primary-100);
    }
    .chat-skeleton__body:nth-of-type(even) & {
      background-color: var(--primary-200);
    }
  }

  &__message-content {
    grid-area: content;
    width: 100%;
  }
  &__message-msg {
    height: 13px;
    border-radius: $radius;
    margin: 5px 0;

    .chat-skeleton__body:nth-of-type(odd) & {
      background-color: var(--primary-100);
    }
    .chat-skeleton__body:nth-of-type(even) & {
      background-color: var(--primary-200);
    }
  }

  *[class^="chat-skeleton__message-"] {
    position: relative;
    overflow: hidden;
  }

  &.-animation {
    position: relative;
    overflow: hidden;

    *[class^="chat-skeleton__message-"]:not(.chat-skeleton__message-content):after {
      position: absolute;
      top: 0;
      right: 0;
      bottom: 0;
      left: 0;
      transform: translateX(-100%);
      background: linear-gradient(
        90deg,
        rgba(var(--chat-skeleton-animation-rgb), 0) 0,
        rgba(var(--chat-skeleton-animation-rgb), 0.3) 50%,
        rgba(var(--chat-skeleton-animation-rgb), 0.5) 100%
      );
      animation: shimmer 1.25s infinite;
      content: "";
    }

    @keyframes shimmer {
      100% {
        transform: translateX(100%);
      }
    }
  }
}