/* ============================================================================
   extras.css — System Rail (chapter conduit) + cursor-reactive grid glow
   ============================================================================ */

/* ── cursor-reactive ambient glow ── */
.cursor-glow {
  position: fixed;
  top: 0; left: 0;
  width: 760px; height: 760px;
  margin: -380px 0 0 -380px;
  border-radius: 50%;
  background: radial-gradient(circle, color-mix(in oklch, var(--accent) 10%, transparent), transparent 62%);
  pointer-events: none;
  z-index: 0;
  opacity: 0;
  transition: opacity .6s var(--ease);
  will-change: transform;
  mix-blend-mode: screen;
}
.cursor-glow.on { opacity: 1; }
@media (hover: none) { .cursor-glow { display: none; } }

/* ── System Rail ── */
.srail {
  position: fixed;
  right: 26px;
  top: 50%;
  transform: translateY(-50%);
  height: min(62vh, 520px);
  width: 14px;
  z-index: 900;
}
.srail-line {
  position: absolute; left: 50%; transform: translateX(-50%);
  top: 0; bottom: 0; width: 2px;
  border-radius: 2px;
  background: var(--line-2);
  overflow: visible;
}
.srail-fill {
  position: absolute; left: 0; top: 0; width: 100%;
  border-radius: 2px;
  background: linear-gradient(var(--accent), color-mix(in oklch, var(--accent) 30%, transparent));
  box-shadow: 0 0 12px var(--accent-glow);
}
.srail-packet {
  position: absolute; left: 50%; width: 4px; height: 4px; margin-left: -2px;
  border-radius: 50%; background: var(--accent);
  box-shadow: 0 0 8px var(--accent-glow);
  animation: srailPacket 3.4s linear infinite;
}
.srail-packet.p2 { animation-delay: 1.13s; }
.srail-packet.p3 { animation-delay: 2.26s; }
@keyframes srailPacket {
  0% { top: 0; opacity: 0; }
  8% { opacity: 1; }
  92% { opacity: 1; }
  100% { top: 100%; opacity: 0; }
}

.srail-nodes {
  position: absolute; inset: 0;
  display: flex; flex-direction: column; justify-content: space-between; align-items: center;
}
.srail-node {
  position: relative;
  display: flex; align-items: center; justify-content: center;
  width: 22px; height: 22px;
  background: transparent; border: 0; padding: 0; cursor: pointer;
}
.srn-dot {
  width: 9px; height: 9px; border-radius: 50%;
  background: var(--bg); border: 1.5px solid var(--line-3);
  transition: background .3s var(--ease), border-color .3s var(--ease), box-shadow .3s var(--ease), transform .3s var(--ease);
}
.srail-node.done .srn-dot { border-color: var(--accent-line); background: color-mix(in oklch, var(--accent) 30%, var(--bg)); }
.srail-node.active .srn-dot {
  background: var(--accent); border-color: var(--accent);
  box-shadow: 0 0 0 4px var(--bg), 0 0 14px var(--accent-glow);
  transform: scale(1.15);
}
.srail-node:hover .srn-dot { border-color: var(--accent); }

.srn-label {
  position: absolute; right: 26px; top: 50%;
  transform: translateY(-50%) translateX(8px);
  display: inline-flex; align-items: center; gap: 9px;
  white-space: nowrap;
  font-size: 13px; color: var(--text-2);
  padding: 6px 11px; border-radius: 8px;
  background: color-mix(in oklch, var(--surface) 86%, transparent);
  border: 1px solid var(--line);
  -webkit-backdrop-filter: blur(8px); backdrop-filter: blur(8px);
  opacity: 0; pointer-events: none;
  transition: opacity .25s var(--ease), transform .25s var(--ease);
}
.srn-n { font-size: 10px; color: var(--accent); letter-spacing: 0.04em; }
.srail-node:hover .srn-label,
.srail-node.active .srn-label { opacity: 1; transform: translateY(-50%) translateX(0); }
.srail-node.active .srn-label { color: var(--text); border-color: var(--line-2); }

/* a soft "you are here" tick connecting active node to its label */
.srail-node.active::after {
  content: ""; position: absolute; right: 18px; top: 50%; width: 8px; height: 1px;
  background: var(--accent-line); transform: translateY(-50%);
}

@media (max-width: 1180px) { .srail { display: none; } }
@media (prefers-reduced-motion: reduce) {
  .srail-packet { animation: none; opacity: 0; }
  .cursor-glow { display: none; }
}