:root {
  --background-color: #333;
  --spinner-primary-color: white;
  --spinner-secondary-color: #ccc;
  --error-text-color: #ffdddd;
  --overlay-bg-color: rgba(0, 0, 0, 0.7);

  --transition-duration-slow: 1s;
  --transition-duration-fast: 0.5s;
}

html, body {
  margin: 0;
  padding: 0;
  background-color: var(--background-color);
  width: 100%;
  height: 100%;
  overflow: hidden;
  font-family: sans-serif;
}

iframe {
  position: absolute;
  top: 0;
  left: 0;
  width: 100vw;
  height: 100vh;
  border: none;
  margin: 0;
  padding: 0;
  opacity: 1;
  transition: opacity var(--transition-duration-slow) ease;
}

#overlay {
  position: absolute;
  top: 0;
  left: 0;
  width: 100vw;
  height: 100vh;
  background-color: var(--overlay-bg-color);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  opacity: 0;
  pointer-events: none;
  transition: opacity var(--transition-duration-fast) ease;
}

#overlay.active {
  opacity: 1;
  pointer-events: auto;
}

.spinner {
  width: 80px;
  height: 80px;
  border: 16px solid var(--spinner-secondary-color);
  border-top: 16px solid var(--spinner-primary-color);
  border-radius: 50%;
  animation: spin var(--transition-duration-slow) linear infinite;
}

.error-message {
  color: var(--error-text-color);
  margin-top: 20px;
  display: none;
}

@keyframes spin {
  from { transform: rotate(0deg); }
  to { transform: rotate(360deg); }
}