.slide-viewer {
  max-width: 800px;
  margin: 1rem auto;
}
.slide-controls {
  display: flex;
  gap: .5rem;
  align-items: center;
  margin-bottom: .75rem;
}
.slide-controls label {
  font-weight: 600;
}
.slide-square {
  position: relative;
  width: 100%;
  aspect-ratio: 16/9;
  border: 2px solid #444;
  border-radius: 8px;
  overflow: hidden;
  background: #fff;
  box-shadow: 0 6px 18px rgba(0, 0, 0, 0.08);
}
.slide-square iframe {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  border: 0;
}
@supports not (aspect-ratio: 16/9) {
  .slide-square { padding-top: 100%; }
  .slide-square iframe { position: absolute; inset: 0; }
}