html, body {
  margin: 0;
  padding: 0;
  width: 100%;
  height: 100%;
  overflow: hidden;
  background: #000;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
}

a-scene {
  width: 100%;
  height: 100%;
}

#overlay-ui {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  z-index: 10;
  display: flex;
  flex-direction: column;
  align-items: center;
  pointer-events: none;
}

#scan-hint {
  margin-top: env(safe-area-inset-top, 16px);
  margin-top: calc(env(safe-area-inset-top, 0px) + 16px);
  padding: 10px 18px;
  background: rgba(0, 0, 0, 0.6);
  color: #fff;
  font-size: 14px;
  border-radius: 20px;
  transition: opacity 0.3s ease;
}

#scan-hint.hidden {
  opacity: 0;
}

#sound-btn {
  margin-top: 10px;
  padding: 8px 16px;
  border: none;
  border-radius: 20px;
  background: rgba(0, 0, 0, 0.6);
  color: #fff;
  font-size: 13px;
  pointer-events: auto;
}

.hidden {
  display: none !important;
}