body {
  font-family: sans-serif;
  background: #111;
  color: #eee;
  margin: 0;
  padding: 0;
}

header {
  background: #222;
  padding: 10px;
  text-align: center;
}

nav button {
  margin: 5px;
  padding: 10px;
  background: #444;
  color: #fff;
  border: none;
  cursor: pointer;
}

nav button:hover {
  background: #666;
}

.tab {
  padding: 20px;
}

.hidden {
  display: none;
}

#room-list, #ranking-list, #profile-info {
  background: #1a1a1a;
  padding: 15px;
  border-radius: 8px;
}