* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
  user-select: none;
  -webkit-user-select: none;
}
body, html {
  width: 100%;
  height: 100%;
  overflow: hidden;
  font-family: 'Segoe UI', -apple-system, BlinkMacSystemFont, Roboto, sans-serif;
  background: #0f1115;
  color: #f0f3f6;
}
#canvas3d {
  width: 100%;
  height: 100%;
  display: block;
}

/* UI Overlay */
.ui-layer {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  pointer-events: none;
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  padding: 20px;
  z-index: 10;
}
.top-bar {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  pointer-events: auto;
}
.brand-card {
  background: rgba(18, 22, 28, 0.78);
  backdrop-filter: blur(14px);
  -webkit-backdrop-filter: blur(14px);
  border: 1px solid rgba(255, 255, 255, 0.12);
  border-radius: 14px;
  padding: 14px 20px;
  box-shadow: 0 10px 30px rgba(0,0,0,0.35);
}
.brand-card h1 {
  font-size: 1.15rem;
  font-weight: 600;
  letter-spacing: 0.5px;
  display: flex;
  align-items: center;
  gap: 8px;
}
.brand-card p {
  font-size: 0.78rem;
  color: #9ba3af;
  margin-top: 3px;
}
.action-group {
  display: flex;
  gap: 10px;
}
.glass-btn {
  background: rgba(18, 22, 28, 0.78);
  backdrop-filter: blur(14px);
  border: 1px solid rgba(255, 255, 255, 0.14);
  color: #fff;
  padding: 10px 16px;
  border-radius: 12px;
  font-size: 0.82rem;
  font-weight: 500;
  cursor: pointer;
  transition: all 0.22s ease;
  display: flex;
  align-items: center;
  gap: 8px;
  box-shadow: 0 4px 15px rgba(0,0,0,0.25);
}
.glass-btn:hover {
  background: rgba(255, 255, 255, 0.14);
  border-color: rgba(255, 255, 255, 0.3);
  transform: translateY(-2px);
}
.glass-btn.active {
  background: linear-gradient(135deg, #2b6cb0, #3182ce);
  border-color: #63b3ed;
}

/* Room quick navigation bar */
.bottom-bar {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 12px;
  pointer-events: auto;
  margin-bottom: 8px;
}
.room-nav {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 8px;
  background: rgba(15, 18, 24, 0.82);
  backdrop-filter: blur(16px);
  border: 1px solid rgba(255, 255, 255, 0.12);
  padding: 8px 14px;
  border-radius: 20px;
  box-shadow: 0 12px 35px rgba(0,0,0,0.4);
  max-width: 95vw;
}
.room-btn {
  background: transparent;
  border: none;
  color: #cbd5e1;
  padding: 8px 14px;
  border-radius: 12px;
  font-size: 0.82rem;
  cursor: pointer;
  transition: all 0.2s;
  display: flex;
  align-items: center;
  gap: 6px;
}
.room-btn:hover {
  background: rgba(255, 255, 255, 0.12);
  color: #ffffff;
}
.room-btn.active {
  background: rgba(255, 255, 255, 0.2);
  color: #ffffff;
  font-weight: 600;
  box-shadow: 0 2px 8px rgba(0,0,0,0.2);
}

/* Floating Help / Controls Info */
.controls-hint {
  position: absolute;
  left: 20px;
  bottom: 25px;
  background: rgba(18, 22, 28, 0.75);
  backdrop-filter: blur(12px);
  border: 1px solid rgba(255, 255, 255, 0.1);
  border-radius: 12px;
  padding: 12px 16px;
  font-size: 0.75rem;
  color: #94a3b8;
  pointer-events: auto;
  line-height: 1.6;
  max-width: 250px;
}
.controls-hint strong {
  color: #f1f5f9;
}
.key-badge {
  display: inline-block;
  padding: 1px 6px;
  background: rgba(255, 255, 255, 0.15);
  border: 1px solid rgba(255, 255, 255, 0.2);
  border-radius: 4px;
  color: #fff;
  font-weight: 600;
  font-size: 0.7rem;
}

/* Crosshair for first person */
#crosshair {
  position: absolute;
  top: 50%;
  left: 50%;
  width: 8px;
  height: 8px;
  transform: translate(-50%, -50%);
  pointer-events: none;
  border-radius: 50%;
  background: rgba(255, 255, 255, 0.5);
  box-shadow: 0 0 6px rgba(0,0,0,0.5);
  display: none;
  z-index: 5;
}
#crosshair::before, #crosshair::after {
  content: '';
  position: absolute;
  background: rgba(255, 255, 255, 0.7);
}
#crosshair::before {
  top: 3px; left: -8px; width: 24px; height: 2px;
}
#crosshair::after {
  top: -8px; left: 3px; width: 2px; height: 24px;
}

/* Room Name Banner */
.room-banner {
  position: absolute;
  top: 90px;
  left: 50%;
  transform: translateX(-50%);
  background: rgba(18, 22, 28, 0.85);
  backdrop-filter: blur(14px);
  border: 1px solid rgba(255, 255, 255, 0.12);
  padding: 8px 22px;
  border-radius: 30px;
  font-size: 0.85rem;
  font-weight: 600;
  letter-spacing: 0.6px;
  color: #38bdf8;
  pointer-events: none;
  opacity: 0;
  transition: opacity 0.4s ease, transform 0.4s ease;
  box-shadow: 0 8px 24px rgba(0,0,0,0.3);
  z-index: 10;
}
.room-banner.show {
  opacity: 1;
  transform: translateX(-50%) translateY(0);
}

/* Loading Screen */
#loader {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: #0d1117;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  z-index: 100;
  transition: opacity 0.6s ease;
}
.spinner {
  width: 54px;
  height: 54px;
  border: 4px solid rgba(255, 255, 255, 0.1);
  border-top-color: #38bdf8;
  border-radius: 50%;
  animation: spin 0.9s linear infinite;
  margin-bottom: 20px;
}
@keyframes spin {
  to { transform: rotate(360deg); }
}
#loader h2 {
  font-size: 1.3rem;
  font-weight: 500;
  letter-spacing: 1px;
}
#loader p {
  font-size: 0.85rem;
  color: #94a3b8;
  margin-top: 6px;
}

@media (max-width: 768px) {
  .controls-hint { display: none; }
  .brand-card h1 { font-size: 0.95rem; }
  .brand-card p { display: none; }
  .room-btn { padding: 6px 10px; font-size: 0.74rem; }
}