client/src/index.scss

:root {
  --main-color: #1f1f1f;
  --secondary-color: white;
  --third-color: #8b8b8b;
  --main-text-color: #3e5869;
  --secondary-text-color: #b0c7d6;
  --send-message-form: #f5f5f5;
  --scroll-bar-bg-color: #04000000;
}

html,
body {
  height: 100%;
  margin: 0;
  padding: 0;
  font-family: "Open Sans", sans-serif;
  font-weight: 200;
  color: #3e5869;
  --scroll-bar-bg-color: rgba(0,0,0,0.2);
}

#root {
  height: 100%;
}

.app {
  display: grid;
  height: 100%;
  grid-template-columns: 320px 1fr;
  grid-template-rows: 40px 50px 1fr;
  grid-template-areas:
    "h m"
    "n m"
    "r m";
}

.messenger {
  grid-area: m;
  display: flex;
  flex-direction: column;
  overflow: hidden;
}

.conversation-header {
  grid-area: h;
  display: flex;
  align-items: center;
  padding-right: 8px;

  .title, .subtitle {
    overflow: hidden;
    text-overflow: ellipsis;
  }
}

.send-message-form {
  margin: 0 16px 16px 8px;
}

.MuiContainer-root {
  padding-bottom: 32px;
}

.login {
  background-color: var(--main-color);
}

.main-search {
  grid-area: n;
}

/* REST OF CSS */

.main-search-input {
  padding: 8px;
  background-color: var(--secondary-color);
  width: 100%;
}

.rooms-list {
  grid-area: r;
  overflow-y: scroll;

  .MuiListItemText-primary,
  .MuiListItemText-secondary {
    overflow: hidden;
    text-overflow: ellipsis;
  }

  scrollbar-color: var(--scroll-bar-bg-color) transparent;
  scrollbar-width: thin;
}
::-webkit-scrollbar {
  -webkit-appearance: none;
  width: 8px;
}
::-webkit-scrollbar-thumb {
    background-color: var(--scroll-bar-bg-color);
    border-radius: 4px;
}

.list-placeholder {
  margin: 32px auto;
  width: 256px;
  text-align: center;

  .subtitle {
    color: #a0a0a0;
  }
}

.message-list {
  flex: 1;
  height: 100%;
  overflow: auto;
  display: flex;
  flex-direction: column-reverse;
  padding: 16px 32px;

  .conversation-event {
    margin: 8px auto;

    .inline-avatar {
      display: inline-block;
      vertical-align: middle;
      margin: 16px;
    }
  }

  .message {
    margin: 8px 0;

    .message-avatar {
      display: inline-block;
      vertical-align: middle;
    }
    .message-username {
      font-size: 11px;
      font-weight: bold;
      color: var(--secondary-color);
      opacity: 0.9;
      margin-bottom: 6px;
    }
    .message-text {
      background: var(--third-color);
      color: var(--secondary-color);
      display: inline;
      padding: 8px 16px;
      border-radius: 16px;
      margin: 8px;
    }
  }
}

.send-message-card {
  border-radius: 8px;
  margin: 16px;
}

.help-text {
  position: absolute;
  top: 10px;
}