* { box-sizing: border-box; }
body {
  margin: 0;
  min-height: 100vh;
  font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  display: grid;
  place-items: center;
  background: #111827;
  color: #f9fafb;
}
.card {
  width: min(92vw, 520px);
  background: #1f2937;
  border: 1px solid #374151;
  border-radius: 20px;
  padding: 28px;
  box-shadow: 0 20px 60px rgba(0,0,0,.35);
}
h1 { margin: 0 0 8px; font-size: 28px; }
.muted { color: #cbd5e1; margin-top: 0; }
button, input {
  font: inherit;
  border-radius: 12px;
  border: 0;
  padding: 13px 16px;
}
button {
  cursor: pointer;
  background: #2563eb;
  color: white;
  font-weight: 700;
}
button:hover { filter: brightness(1.08); }
button.secondary { background: #4b5563; }
button.danger { background: #dc2626; }
input {
  width: 100%;
  background: #111827;
  color: white;
  border: 1px solid #4b5563;
  text-transform: uppercase;
}
.join-row {
  display: grid;
  grid-template-columns: 1fr auto;
  gap: 10px;
  margin-top: 12px;
}
.room-box {
  background: #111827;
  border: 1px solid #4b5563;
  padding: 14px;
  border-radius: 14px;
  display: flex;
  align-items: center;
  gap: 12px;
  justify-content: space-between;
}
.controls { display: flex; gap: 10px; margin-top: 18px; }
.error {
  margin-top: 16px;
  color: #fecaca;
  background: #7f1d1d;
  border-radius: 12px;
  padding: 12px;
}
@media (max-width: 520px) {
  .join-row, .controls { grid-template-columns: 1fr; display: grid; }
}