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

.chat-channel {
  display: flex;
  flex-direction: column;
  width: 100%;
  min-height: 1px;
  position: relative;
  overflow: hidden;
  grid-area: main;
  min-width: 250px;
  @include chat-height;

  .chat-messages-scroll {
    flex-grow: 1;
    overflow-y: scroll;
    overscroll-behavior: contain;
    display: flex;
    flex-direction: column-reverse;
    z-index: 1;
    margin: 0 1px 0 0;
    will-change: transform;
    @include chat-scrollbar();
    min-height: 1px;

    .join-channel-btn.in-float {
      position: absolute;
      transform: translateX(-50%);
      left: 50%;
      top: 10px;
      z-index: 10;
    }

    .all-loaded-message {
      text-align: center;
      color: var(--primary-medium);
      font-size: var(--font-down-1);
      padding: 0.5em 0.25em 0.25em;
    }
  }
}