.teach {
  position: absolute;
  inset: 0;
  pointer-events: none;
  z-index: 2;
}

.teach[hidden] { display: none; }

.tape {
  position: absolute;
  left: 32px;
  right: 32px;
  top: 118px;
  display: flex;
  flex-wrap: wrap;
  gap: 4px;
  max-width: min(640px, calc(100% - 64px));
  pointer-events: auto;
}

.tape-cell {
  min-width: 1.6em;
  padding: 3px 5px;
  border: 1px solid var(--line);
  border-radius: 3px;
  background: var(--raised);
  color: var(--muted);
  font-family: var(--font-mono);
  font-size: 12px;
  text-align: center;
}

.tape-cell.pad {
  border-style: dashed;
  opacity: 0.85;
}

.tape-cell.marker { color: var(--accent); }

.tape-cell.on {
  background: var(--accent);
  color: var(--accent-fg);
  border-color: var(--accent);
}

.teach-card {
  position: absolute;
  left: 32px;
  bottom: 72px;
  width: min(420px, calc(100% - 48px));
  padding: 14px 16px 16px;
  border: 1px solid var(--line);
  border-radius: var(--radius-lg);
  background: rgba(12, 12, 14, 0.88);
  pointer-events: auto;
}

.stage:has(#caption) .teach-card {
  top: 118px;
  bottom: auto;
  width: min(380px, calc(100% - 48px));
  padding: 12px 14px 14px;
}

.teach-card .kicker {
  margin: 0 0 6px;
  font-family: var(--font-mono);
  font-size: 12px;
  color: var(--muted);
}

.teach-card h2 {
  margin: 0 0 8px;
  font-family: var(--font-display);
  font-weight: 520;
  font-size: 22px;
  letter-spacing: -0.02em;
}

.teach-card .math,
.teach-card .why {
  margin: 0 0 8px;
  font-size: 15px;
  line-height: 1.45;
}

.teach-card .math { font-family: var(--font-mono); font-size: 13px; color: var(--fg); }

.teach-card .why { color: var(--muted); }

.transport {
  position: absolute;
  left: 32px;
  right: 32px;
  bottom: 16px;
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 8px;
  pointer-events: auto;
}

.transport .pos {
  font-family: var(--font-mono);
  font-size: 12px;
  color: var(--muted);
  min-width: 5.5em;
}

.outline {
  overflow: auto;
  max-height: 28vh;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--bg);
  padding: 6px 0;
}

.outline[hidden] { display: none; }

.outline details { padding: 0 8px 6px; }

.outline summary {
  cursor: pointer;
  color: var(--muted);
  font-family: var(--font-mono);
  font-size: 12px;
  padding: 4px 0;
}

.outline-item {
  display: block;
  width: 100%;
  text-align: left;
  border: 0;
  background: transparent;
  color: var(--fg);
  padding: 4px 8px;
  border-radius: var(--radius);
}

.outline-item:hover { background: var(--accent-soft); border-color: transparent; }

.outline-item.on {
  background: var(--accent-soft);
  color: var(--accent);
}

@media (max-width: 900px) {
  .tape { top: 96px; left: 16px; right: 16px; }
  .teach-card { left: 16px; bottom: 64px; }
  .transport { left: 16px; right: 16px; }
  .outline { max-height: 22vh; }
}