/* ============================================================
   Navigation buttons (edge arrows) + Help overlay.
   ============================================================ */

/* Edge-pinned navigation arrows. Hidden until the stage is hovered. */
.nav-btn {
  position: absolute;
  top: 50%;
  transform: translateY(-50%);
  width: 40px; height: 64px;
  background: transparent;
  border: 1px solid var(--border-2);
  color: var(--text-dim);
  font-size: 20px;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  opacity: 0;
  transition:
    opacity 200ms,
    background 200ms,
    color 200ms,
    border-color 200ms,
    box-shadow 200ms,
    transform 200ms;
  z-index: 200;
  font-family: var(--mono);
}
#stage:hover .nav-btn { opacity: 1; }
.nav-btn:hover {
  background: var(--accent);
  color: var(--bg);
  border-color: var(--accent);
  box-shadow: var(--shadow-accent);
  transform: translateY(-50%) scale(1.04);
}
.nav-btn:active { transform: translateY(-50%) scale(0.98); }
.nav-btn:focus-visible {
  opacity: 1;
  outline: none;
  box-shadow: var(--focus-ring);
}
.nav-btn.prev { left: 16px; }
.nav-btn.next { right: 16px; }

/* Help overlay — frosted backdrop, surface card. */
#help {
  position: absolute;
  inset: 0;
  background: rgba(10,10,10,0.82);
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
  display: none;
  align-items: center;
  justify-content: center;
  z-index: 500;
  padding: 80px;
}
#help.show { display: flex; }

.help-box {
  border: 1px solid var(--border-2);
  background: var(--surface);
  padding: 48px 64px;
  max-width: 720px;
  width: 100%;
  box-shadow:
    0 24px 64px -16px rgba(0,0,0,0.6),
    0 0 0 1px rgba(255,107,31,0.08);
}
.help-box h2 {
  font-family: var(--display);
  font-size: 56px;
  line-height: 1;
  letter-spacing: -0.01em;
  margin-bottom: 32px;
  color: var(--text);
  text-transform: uppercase;
}
.help-row {
  display: grid;
  grid-template-columns: 200px 1fr;
  padding: 12px 0;
  border-bottom: 1px solid var(--border);
  font-size: 16px;
}
.help-row:last-child { border-bottom: none; }
.help-row .keys { display: flex; gap: 6px; }
.help-row .keys .kbd {
  font-size: 11px;
  padding: 2px 8px;
  color: var(--text);
  border-color: var(--border-3);
}