.chapter-rail{width:calc(100% - var(--system-gutter) * 2);max-width:var(--system-width);pointer-events:none;z-index:102;margin-inline:auto;position:fixed;inset:0}.chapter-rail nav{pointer-events:auto;position:absolute;top:50%;left:0;translate:-50% -50%}.chapter-rail ol{flex-direction:column;gap:1px;margin:0;padding:8px 0;list-style:none;display:flex}.chapter-rail a{width:28px;height:22px;color:var(--text-faint);place-items:center;text-decoration:none;display:grid;position:relative}.chapter-rail-mark{border:1px solid var(--text-faint);background:var(--bg);width:7px;height:7px;transition:background var(--ease-fast), border-color var(--ease-fast), rotate var(--ease-base) var(--motion-curve), scale var(--ease-base) var(--motion-curve)}.chapter-rail a.is-past .chapter-rail-mark{background:var(--text-faint);border-color:var(--text-faint)}.chapter-rail a[aria-current] .chapter-rail-mark{background:var(--accent);border-color:var(--accent);rotate:45deg;scale:1.25}.chapter-rail a:hover .chapter-rail-mark{border-color:var(--accent)}.chapter-rail-n{font:9px var(--font-ibm-plex-mono),monospace;letter-spacing:.06em;font-variant-numeric:tabular-nums;opacity:0;transition:opacity var(--ease-fast), translate var(--ease-fast), color var(--ease-fast);position:absolute;right:calc(100% - 2px);translate:4px}.chapter-rail nav:hover .chapter-rail-n,.chapter-rail nav:focus-within .chapter-rail-n,.chapter-rail a[aria-current] .chapter-rail-n{opacity:1;translate:0}.chapter-rail a[aria-current] .chapter-rail-n{color:var(--accent-content)}.chapter-rail-name{white-space:nowrap;background:var(--bg);border:1px solid var(--border);color:var(--text);opacity:0;pointer-events:none;transition:opacity var(--ease-fast), translate var(--ease-fast);padding:5px 9px;font-size:11px;position:absolute;left:calc(100% + 4px);translate:-4px}.chapter-rail a:is(:hover,:focus-visible) .chapter-rail-name{opacity:1;translate:0}.chapter-rail a:focus-visible{outline:1px solid var(--accent);outline-offset:0}.chapter-rail-progress{background:var(--accent);width:1px;transform:scaleY(var(--progress,0));transform-origin:top;position:absolute;top:0;bottom:0;right:0}.chapter-rail-bar{display:none}.chapter-rail-bus{width:1px;position:absolute;top:0;bottom:0;left:0;overflow:hidden}.chapter-rail-bus i{background:linear-gradient(transparent, var(--accent));width:1px;height:90px;animation:7s cubic-bezier(.45,0,.2,1) infinite rail-bus;position:absolute;top:0;left:0;translate:0 -90px}@keyframes rail-bus{to{translate:0 100vh}}.chapter-here{width:calc(100% - var(--system-gutter) * 2);max-width:var(--system-width);pointer-events:none;z-index:100;height:60px;margin-inline:auto;position:fixed;top:0;left:0;right:0}.chapter-here-cell{align-items:center;gap:12px;width:25%;padding:0 18px;display:flex;position:absolute;top:0;bottom:1px;left:33.3333%;overflow:hidden}.chapter-here-label{font:9px var(--font-ibm-plex-mono),monospace;letter-spacing:.14em;color:var(--text-faint)}.chapter-here-value{min-width:0;animation:here-in .5s var(--motion-curve) both;align-items:baseline;gap:8px;display:flex}.chapter-here-value b{font:500 11px var(--font-ibm-plex-mono),monospace;color:var(--accent-content)}.chapter-here-value span{white-space:nowrap;text-overflow:ellipsis;color:var(--text);font-size:12px;overflow:hidden}.chapter-here-ticks{align-items:flex-end;gap:2px;margin-left:auto;display:flex}.chapter-here-ticks i{background:var(--border);transform-origin:bottom;width:3px;height:14px;transition:background var(--ease-base), transform var(--ease-base) var(--motion-curve);transform:scaleY(.7)}.chapter-here-ticks i.is-past{background:var(--text-faint)}.chapter-here-ticks i.is-current{background:var(--accent);transform:scaleY(1)}@keyframes here-in{0%{opacity:0;translate:0 10px}}.chapter-chip{display:none}@media (max-width:1180px){.chapter-here-ticks{display:none}}@media (max-width:1023px){.chapter-here{display:none}.chapter-chip{border:1px solid var(--border);background:var(--bg);color:var(--text);white-space:nowrap;opacity:0;transition:opacity .3s ease, translate .4s var(--motion-curve);align-items:center;gap:8px;padding:7px 12px;font-size:12px;display:flex;position:absolute;top:70px;left:50%;translate:-50% -8px}.chapter-chip b{font:500 10px var(--font-ibm-plex-mono),monospace;color:var(--accent-content)}.chapter-chip.is-on{opacity:1;translate:-50%}.chapter-rail nav,.chapter-rail-progress,.chapter-rail-bus{display:none}.chapter-rail-bar{background:var(--accent);height:1px;transform:scaleX(var(--progress,0));transform-origin:0;display:block;position:absolute;top:60px;left:0;right:0}}@media (prefers-reduced-motion:reduce){.chapter-rail-mark,.chapter-rail-n,.chapter-rail-name,.chapter-chip{transition:none}.chapter-rail-bus,.chapter-here-value{animation:none}}@media print{.chapter-here,.chapter-rail{display:none}}