/* ============================================================
   rail.css — the signature "readout rail": a vertical trace
   running down the page that lights up as you scroll, with
   docked section labels acting like instrument readings.
   ============================================================ */

/* ── Top bar: logo + menu toggle (mobile) ──────────────────── */
.topbar {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 60;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 18px var(--edge);
  background: linear-gradient(to bottom, rgba(11, 14, 17, 0.92), rgba(11, 14, 17, 0));
  pointer-events: none;
}

.topbar > * {
  pointer-events: auto;
}

.topbar__mark {
  font-family: var(--font-mono);
  font-size: 13px;
  letter-spacing: 0.08em;
  color: var(--paper);
  display: flex;
  align-items: center;
  gap: 8px;
  text-decoration: none;
}

.topbar__mark .dot {
  width: 7px;
  height: 7px;
  border-radius: 50%;
  background: var(--signal);
  box-shadow: 0 0 8px var(--signal-glow);
  animation: blink 2.6s ease-in-out infinite;
}

@keyframes blink {
  0%, 100% { opacity: 1; }
  50% { opacity: 0.35; }
}

.topbar__toggle {
  display: flex;
  flex-direction: column;
  gap: 5px;
  padding: 10px;
  z-index: 70;
}

.topbar__toggle span {
  width: 22px;
  height: 1.5px;
  background: var(--paper);
  transition: transform 0.3s var(--ease-out), opacity 0.3s var(--ease-out);
}

.topbar__toggle[aria-expanded="true"] span:nth-child(1) {
  transform: translateY(6.5px) rotate(45deg);
}
.topbar__toggle[aria-expanded="true"] span:nth-child(2) {
  opacity: 0;
}
.topbar__toggle[aria-expanded="true"] span:nth-child(3) {
  transform: translateY(-6.5px) rotate(-45deg);
}

/* ── The rail itself: fixed vertical trace, desktop only ───── */
.rail {
  position: fixed;
  top: 0;
  left: var(--rail-x);
  bottom: 0;
  width: 1px;
  z-index: 40;
  display: none;
}

@media (min-width: 980px) {
  .rail {
    display: block;
  }
}

.rail__track {
  position: absolute;
  inset: 0;
  background: var(--hairline);
}

.rail__fill {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 0%;
  background: linear-gradient(to bottom, var(--signal), var(--signal-dim));
  box-shadow: 0 0 12px var(--signal-glow);
  transition: height 0.08s linear;
}

.rail__nodes {
  position: absolute;
  inset: 0;
}

.rail__node {
  position: absolute;
  left: 50%;
  transform: translate(-50%, -50%);
  width: 9px;
  height: 9px;
  border-radius: 50%;
  background: var(--ink);
  border: 1.5px solid var(--instrument-dim);
  transition: border-color 0.25s var(--ease-out), background 0.25s var(--ease-out),
    box-shadow 0.25s var(--ease-out);
}

.rail__node.is-active {
  border-color: var(--signal);
  background: var(--signal);
  box-shadow: 0 0 10px var(--signal-glow);
}

.rail__label {
  position: absolute;
  left: 22px;
  transform: translateY(-50%);
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--instrument-dim);
  white-space: nowrap;
  text-decoration: none;
  transition: color 0.25s var(--ease-out), letter-spacing 0.25s var(--ease-out);
}

.rail__label:hover {
  color: var(--paper);
}

.rail__label.is-active {
  color: var(--signal);
}

/* ── Mobile nav drawer ───────────────────────────────────── */
.mobile-nav {
  position: fixed;
  inset: 0;
  z-index: 65;
  background: var(--ink-soft);
  display: flex;
  flex-direction: column;
  justify-content: center;
  padding: var(--edge);
  gap: 28px;
  transform: translateY(-100%);
  transition: transform 0.45s var(--ease-out);
}

.mobile-nav.is-open {
  transform: translateY(0);
}

.mobile-nav a {
  font-family: var(--font-display);
  font-size: clamp(1.6rem, 7vw, 2.4rem);
  text-decoration: none;
  color: var(--paper);
  display: flex;
  align-items: baseline;
  gap: 14px;
}

.mobile-nav a .tag {
  font-family: var(--font-mono);
  font-size: 12px;
  color: var(--signal);
}

@media (min-width: 980px) {
  .mobile-nav,
  .topbar__toggle {
    display: none;
  }
}