discourse/plugins/chat/assets/stylesheets/common/chat-message-separator.scss

.chat-message-separator {
  @include unselectable;
  display: flex;

  &-new {
    position: relative;
    padding: 20px 0;

    .chat-message-separator__text-container {
      text-align: center;
      position: absolute;
      height: 40px;
      width: 100%;
      box-sizing: border-box;
      z-index: 1;
      top: 0;
      display: flex;
      align-items: center;
      justify-content: center;

      .chat-message-separator__text {
        color: var(--danger-medium);
        background-color: var(--secondary);
        padding: 0.25rem 0.5rem;
        font-size: var(--font-down-1);
      }
    }

    .chat-message-separator__line-container {
      width: 100%;

      .chat-message-separator__line {
        border-top: 1px solid var(--danger-medium);
      }
    }
  }

  &-date {
    position: absolute;
    width: 100%;
    z-index: 2;
    display: flex;
    align-items: flex-start;
    justify-content: center;
    pointer-events: none;

    &.with-last-visit {
      & + .chat-message-separator__line-container {
        .chat-message-separator__line {
          border-color: var(--danger-medium);
        }
      }
    }

    .chat-message-separator__text-container {
      padding-top: 7px;
      position: sticky;
      top: -1px;

      &.is-pinned,
      &.is-force-pinned {
        .chat-message-separator__text {
          border: 1px solid var(--primary-medium);
          border-radius: 3px;
        }

        .chat-message-separator__last-visit {
          display: none;
        }
      }
    }

    .chat-message-separator__text {
      @include unselectable;
      background-color: var(--secondary);
      border: 1px solid transparent;
      color: var(--secondary-low);
      font-size: var(--font-down-1);
      padding: 0.25rem 0.5rem;
      box-sizing: border-box;
      display: flex;
    }

    & + .chat-message-separator__line-container {
      padding: 20px 0;
      box-sizing: border-box;

      .chat-message-separator__line {
        border-top: 1px solid var(--secondary-high);
        left: 0;
        margin: 0 0 -1px;
        position: relative;
        right: 0;
        top: -1px;
      }
    }
  }
}