/* Navigation owns its layout and control scale independently of the reader. */
:root {
  --rail-w: clamp(20rem, 24vw, 22.5rem);
  --nav-canvas: #fff;
  --nav-surface: #f6f3ef;
  --nav-ink: #211c18;
  --nav-muted: #655d55;
  --nav-line: #ded8d1;
  --nav-control-line: #a69d92;
  --nav-accent: #a73510;
  --nav-selected: #fff0e6;
  --nav-dock-h: calc(4.25rem + env(safe-area-inset-bottom, 0px));
}

:root[data-theme="dark"] {
  --nav-canvas: #000;
  --nav-surface: #1a1714;
  --nav-ink: #ede7df;
  --nav-muted: #b2a99e;
  --nav-line: #36312b;
  --nav-control-line: #81766b;
  --nav-accent: #ffa77e;
  --nav-selected: #2b1a10;
}

#rail [hidden],
.nav-context[hidden],
.nav-mobile [hidden],
.nav-search [hidden] { display: none !important; }

.rail {
  height: calc(100dvh - var(--bar-h));
  padding: 0;
  color: var(--nav-ink);
  background: var(--nav-canvas);
  border-right: 1px solid var(--nav-line);
}

.rail .rail__card {
  border: 0;
  border-radius: 0;
  box-shadow: none;
  background: var(--nav-canvas);
}

.nav-header { flex: none; }

.nav-head {
  display: flex;
  flex: none;
  align-items: center;
  justify-content: space-between;
  gap: .75rem;
  padding: 1.25rem 1.25rem .75rem;
}

.nav-head h2 {
  color: var(--nav-ink);
  font-size: 1.375rem;
  font-weight: 650;
  line-height: 1.3;
  letter-spacing: -.025em;
}

.nav-close,
.nav-search__close {
  display: inline-flex;
  flex: none;
  align-items: center;
  justify-content: center;
  width: 2.75rem;
  height: 2.75rem;
  border: 1px solid transparent;
  border-radius: .5rem;
  color: var(--nav-muted);
}

.nav-close { display: none; }

:is(.nav-close, .nav-search-trigger, .nav-global-search, .nav-mobile button, .nav-steps a, .nav-search__close) svg {
  width: 1.25rem;
  height: 1.25rem;
  flex: none;
  fill: none;
  stroke: currentColor;
  stroke-width: 1.8;
  stroke-linecap: round;
  stroke-linejoin: round;
}

.nav-search-trigger,
.nav-global-search {
  display: flex;
  align-items: center;
  gap: .625rem;
  min-height: 2.75rem;
  min-width: 0;
  padding: .5rem .75rem;
  border: 1px solid var(--nav-control-line);
  border-radius: .625rem;
  background: var(--nav-canvas);
  color: var(--nav-muted);
  font-size: .9375rem;
  font-weight: 500;
  text-align: left;
}

.nav-search-trigger {
  flex: none;
  width: calc(100% - 2rem);
  margin: 0 1rem 1rem;
}

.nav-search-trigger span,
.nav-global-search span { flex: 1; }

:is(.nav-search-trigger, .nav-global-search, .nav-search__hint) kbd {
  padding: .125rem .3rem;
  border: 1px solid var(--nav-line);
  border-radius: .25rem;
  color: var(--nav-muted);
  background: var(--nav-canvas);
  font-family: inherit;
  font-size: .75rem;
  line-height: 1.4;
  white-space: nowrap;
}

.nav-global-search {
  width: clamp(10rem, 20vw, 19rem);
  margin-right: auto;
  margin-left: clamp(.5rem, 2vw, 2rem);
}

.nav-tabs {
  display: grid;
  flex: none;
  grid-template-columns: 1fr 1fr;
  gap: .25rem;
  margin: 0 1rem .875rem;
  padding: .25rem;
  border-radius: .625rem;
  background: var(--nav-surface);
}

.nav-tab {
  min-height: 2.75rem;
  min-width: 0;
  padding: .5rem;
  border: 1px solid transparent;
  border-radius: .4375rem;
  color: var(--nav-muted);
  font-size: .9375rem;
  font-weight: 600;
  line-height: 1.3;
}

.nav-tab[aria-selected="true"] {
  border-color: var(--nav-line);
  color: var(--nav-ink);
  background: var(--nav-canvas);
}

.nav-panel {
  display: flex;
  flex: 1;
  flex-direction: column;
  min-height: 0;
  min-width: 0;
  overflow: hidden;
}

.nav-filter {
  display: flex;
  flex: none;
  flex-direction: column;
  gap: .375rem;
  padding: 0 1rem;
}

.nav-filter label {
  color: var(--nav-muted);
  font-size: .8125rem;
  font-weight: 600;
  line-height: 1.4;
}

.nav-filter select {
  width: 100%;
  min-height: 2.75rem;
  padding: .5rem .625rem;
  border: 1px solid var(--nav-control-line);
  border-radius: .5rem;
  color: var(--nav-ink);
  background: var(--nav-canvas);
  font-size: 1rem;
  line-height: 1.4;
  cursor: pointer;
}

.nav-tools {
  display: flex;
  flex: none;
  flex-wrap: wrap;
  align-items: center;
  gap: .375rem;
  padding: .5rem 1rem .625rem;
  border-bottom: 1px solid var(--nav-line);
}

.nav-tools button {
  min-height: 2.75rem;
  padding: .375rem .8125rem;
  border: 1px solid transparent;
  border-radius: .5rem;
  color: var(--nav-muted);
  font-size: .875rem;
  font-weight: 600;
}

.nav-tools button[aria-pressed="true"] {
  color: var(--nav-accent);
  background: var(--nav-selected);
  border-color: currentColor;
}

#nav-result-count { margin-left: auto; color: var(--nav-muted); font-size: .75rem; line-height: 1.4; }

.rail .rail__scroll {
  flex: 1;
  min-height: 0;
  padding: .75rem .625rem 1.5rem;
  overflow: auto;
  overscroll-behavior: contain;
  scrollbar-gutter: stable;
  scrollbar-width: thin;
  scroll-padding-block: .75rem;
}

.rail .tree__domain + .tree__domain {
  margin-top: 1.25rem;
  padding-top: 1.25rem;
  border-color: var(--nav-line);
}

.rail :is(.tree__domainhead, .tree__phasehead) {
  margin: 0 0 .375rem;
  padding: .375rem .625rem;
  color: var(--nav-muted);
  font-family: var(--font-body);
  font-size: .75rem;
  font-weight: 650;
  line-height: 1.45;
  letter-spacing: .075em;
}

.rail .tree__sec + .tree__sec { margin-top: .75rem; }
.rail .tree__phase + .tree__phase { margin-top: .75rem; padding-top: .75rem; border-color: var(--nav-line); }
.rail .tnode--sec { min-height: 2.75rem; padding: .625rem; gap: .5rem; }
.rail .tnode--sec .eyebrow {
  color: var(--nav-ink);
  font-family: var(--font-body);
  font-size: .875rem;
  font-weight: 650;
  line-height: 1.4;
  text-transform: none;
  letter-spacing: 0;
}

.rail .tnode--note { padding-left: 0; align-items: flex-start; }
.rail .tnode--note .twist--btn {
  width: 2.75rem;
  min-height: 2.75rem;
  height: 2.75rem;
  margin: 0;
  padding: 0;
  flex: 0 0 2.75rem;
  align-items: center;
  justify-content: center;
  border-radius: .5rem;
  color: var(--nav-muted);
}
.rail .twist--btn::after { display: none; }
.rail .twist__ico { width: 1rem; height: 1rem; stroke-width: 1.8; }
.rail .entry {
  grid-template-columns: minmax(0, 1fr);
  align-items: baseline;
  gap: .375rem;
  min-height: 2.75rem;
  padding: .6875rem .625rem .6875rem .5rem;
  border: 1px solid transparent;
  border-left-width: 2px;
  border-radius: .4375rem;
}
.rail .entry__num {
  color: var(--nav-muted);
  font-family: var(--font-body);
  font-size: .75rem;
  line-height: 1.5;
}
.rail .entry__title {
  color: var(--nav-ink);
  font-size: .9375rem;
  font-weight: 500;
  line-height: 1.5;
  overflow-wrap: anywhere;
  text-wrap: pretty;
}
.rail .entry[aria-current="page"] {
  border-left-color: var(--nav-accent);
  color: var(--nav-accent);
  background: var(--nav-selected);
}
.rail .entry[aria-current="page"] .entry__title { font-weight: 650; }
.rail .entry[aria-current="page"] .entry__num { color: var(--nav-accent); }
.rail .tree__mods { margin-left: 3.25rem; }
.rail .tree__modsin { padding-left: .875rem; border-color: var(--nav-line); }
.rail .mod {
  min-height: 2.75rem;
  padding: .625rem .5rem;
  color: var(--nav-muted);
  font-size: .875rem;
  line-height: 1.45;
}
.rail .mod[data-current="true"] { color: var(--nav-accent); }
.rail .mod[data-current="true"] .mod__tick { background: var(--nav-accent); box-shadow: none; }
.rail .tree__note[data-current="true"] .tree__modsin { border-color: var(--nav-accent); }
.rail[data-open="true"] .tree__domain { animation: none; }

.nav-resume {
  display: flex;
  flex: none;
  flex-direction: column;
  gap: .25rem;
  margin: .75rem 1rem;
  padding: .75rem;
  border: 1px solid var(--nav-line);
  border-radius: .625rem;
  color: var(--nav-ink);
  background: var(--nav-surface);
  font-size: .9375rem;
  font-weight: 600;
  line-height: 1.45;
  overflow-wrap: anywhere;
  text-decoration: none;
}
.nav-resume :is(small, span:first-child) {
  color: var(--nav-muted);
  font-size: .75rem;
  font-weight: 500;
}
.nav-current { flex: none; padding: .375rem 1.25rem 1rem; border-bottom: 1px solid var(--nav-line); }
.nav-current :is(small, span) { display: block; margin-bottom: .375rem; color: var(--nav-muted); font-size: .8125rem; }
.nav-current strong { display: block; color: var(--nav-ink); font-size: 1rem; font-weight: 600; line-height: 1.45; overflow-wrap: anywhere; }
.nav-outline {
  flex: 1;
  min-height: 0;
  overflow: auto;
  overscroll-behavior: contain;
  scrollbar-gutter: stable;
  scrollbar-width: thin;
  padding: .75rem .875rem 1.5rem;
  scroll-padding-block: .75rem;
}
.nav-outline__link,
.nav-outline__top {
  display: block;
  min-height: 2.75rem;
  padding: .6875rem .75rem;
  border-left: 2px solid transparent;
  border-radius: 0 .4375rem .4375rem 0;
  color: var(--nav-muted);
  font-size: .9375rem;
  font-weight: 500;
  line-height: 1.5;
  overflow-wrap: anywhere;
  text-decoration: none;
}
.nav-outline__top { margin-bottom: .375rem; color: var(--nav-ink); font-size: .875rem; }
.nav-outline__link[data-level="1"] { padding-left: 1.5rem; font-size: .875rem; }
.nav-outline__link[aria-current="location"] {
  border-left-color: var(--nav-accent);
  color: var(--nav-accent);
  background: var(--nav-selected);
  font-weight: 600;
}
.nav-empty { margin: 0; padding: 1rem 1.25rem; color: var(--nav-muted); font-size: .9375rem; line-height: 1.6; }
.rail .rail__foot { flex: none; padding: .5rem 1.25rem; border-color: var(--nav-line); }
.rail .rail__footlabel { color: var(--nav-muted); font-family: var(--font-body); text-transform: none; letter-spacing: 0; font-size: .875rem; }

/* The current lesson's place and adjacent lessons remain easy to find. */
.nav-context {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: .625rem 1rem;
  flex-wrap: wrap;
  margin: 0 0 1.5rem;
  padding-bottom: .875rem;
  border-bottom: 1px solid var(--nav-line);
}
.nav-crumbs { display: flex; flex-wrap: wrap; align-items: center; gap: .125rem .375rem; min-width: 0; color: var(--nav-muted); font-size: .875rem; line-height: 1.45; }
.nav-crumbs :is(a, button) { display: inline-flex; align-items: center; min-height: 2.75rem; padding: .25rem .375rem; border-radius: .375rem; color: var(--nav-muted); font-weight: 500; text-align: left; overflow-wrap: anywhere; }
.nav-crumbs > span { overflow-wrap: anywhere; }
.nav-crumbs > span[aria-current] { color: var(--nav-ink); font-weight: 600; }
.nav-steps { display: flex; flex: none; align-items: center; gap: .375rem; }
.nav-steps a { display: inline-flex; align-items: center; justify-content: center; gap: .375rem; min-height: 2.75rem; min-width: 2.75rem; padding: .5rem .625rem; border: 1px solid var(--nav-line); border-radius: .5rem; color: var(--nav-ink); font-size: .875rem; font-weight: 500; line-height: 1.3; text-decoration: none; }
.nav-steps a[aria-disabled="true"] { color: var(--nav-muted); opacity: .5; pointer-events: none; }
.nav-position { padding: 0 .25rem; color: var(--nav-muted); font-size: .8125rem; font-variant-numeric: tabular-nums; white-space: nowrap; }
.nav-mobile { display: none; }
body[data-workspace="true"] .nav-mobile { display: none; }
body[data-workspace="true"] .main { padding-bottom: 0; }

/* Native dialog supplies modality and remains above the audio chrome. */
html[data-search-open="true"] { overflow: hidden; }
.nav-search {
  width: min(42.5rem, calc(100% - 2rem));
  max-width: none;
  height: auto;
  max-height: min(45rem, calc(100dvh - 2rem));
  margin: auto;
  padding: 0;
  overflow: hidden;
  border: 1px solid var(--nav-control-line);
  border-radius: 1rem;
  color: var(--nav-ink);
  background: var(--nav-canvas);
  box-shadow: 0 1rem 4rem #0003;
}
.nav-search[open] { display: flex; flex-direction: column; }
.nav-search::backdrop { background: #211c1873; }
:root[data-theme="dark"] .nav-search::backdrop { background: #000b; }
.nav-search__head { display: flex; flex: none; align-items: center; justify-content: space-between; gap: .75rem; padding: 1rem 1.25rem .5rem; }
.nav-search__head h2 { color: var(--nav-ink); font-size: 1.25rem; font-weight: 650; line-height: 1.35; }
.nav-search__eyebrow { margin: 0; color: var(--nav-muted); font-size: .8125rem; font-weight: 500; }
.nav-search__group + .nav-search__group { margin-top: .75rem; padding-top: .75rem; border-top: 1px solid var(--nav-line); }
.nav-search__group > .nav-search__eyebrow { padding: .375rem .875rem; font-family: var(--font-body); line-height: 1.5; letter-spacing: 0; }
.nav-search__list { margin: 0; padding: 0; list-style: none; }
.nav-search__label { position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px; overflow: hidden; clip-path: inset(50%); white-space: nowrap; border: 0; }
.nav-search__inputwrap { display: flex; flex: none; align-items: center; gap: .75rem; margin: 0 1.25rem .75rem; padding: 0 .875rem; border: 1px solid var(--nav-control-line); border-radius: .625rem; background: var(--nav-canvas); }
.nav-search__inputwrap:focus-within { outline: 2px solid var(--nav-accent); outline-offset: 2px; }
.nav-search__inputwrap svg { width: 1.25rem; height: 1.25rem; flex: none; color: var(--nav-muted); fill: none; stroke: currentColor; stroke-width: 1.8; }
.nav-search__input { width: 100%; min-width: 0; min-height: 3.25rem; padding: .75rem 0; border: 0; border-radius: 0; outline: none; color: var(--nav-ink); background: transparent; font-size: 1rem; line-height: 1.5; }
.nav-search__input::placeholder { color: var(--nav-muted); opacity: 1; }
.nav-search__status { flex: none; margin: 0; padding: .125rem 1.25rem .75rem; color: var(--nav-muted); font-size: .8125rem; line-height: 1.5; }
.nav-search__results { flex: 1 1 auto; min-height: 0; overflow: auto; overscroll-behavior: contain; margin: 0; padding: .5rem .75rem .75rem; border-top: 1px solid var(--nav-line); list-style: none; scrollbar-width: thin; scroll-padding-block: .5rem; }
.nav-search__result { display: flex; flex-direction: column; align-items: flex-start; gap: .3125rem; width: 100%; min-height: 3.75rem; margin: .125rem 0; padding: .75rem .875rem; border: 1px solid transparent; border-radius: .5rem; color: var(--nav-ink); background: transparent; text-align: left; text-decoration: none; }
.nav-search__result[aria-selected="true"],
.nav-search__result[data-active="true"] { background: var(--nav-selected); border-color: var(--nav-accent); }
.nav-search__title { display: block; color: var(--nav-ink); font-size: 1rem; font-weight: 600; line-height: 1.5; overflow-wrap: anywhere; }
.nav-search__context { display: block; color: var(--nav-muted); font-size: .8125rem; font-weight: 400; line-height: 1.5; overflow-wrap: anywhere; }
.nav-search mark { padding: 0; color: var(--nav-accent); background: transparent; font-weight: 700; }
.nav-search__empty { margin: 0; padding: 1.5rem .75rem; color: var(--nav-muted); font-size: .9375rem; line-height: 1.6; }
.nav-search__hint { display: flex; flex: none; flex-wrap: wrap; align-items: center; gap: .375rem; margin: 0; padding: .75rem 1.25rem; border-top: 1px solid var(--nav-line); color: var(--nav-muted); font-size: .75rem; line-height: 1.6; }

:is(#rail, .nav-context, .nav-mobile, .nav-search) :is(a, button, select):focus-visible,
.nav-global-search:focus-visible { outline: 2px solid var(--nav-accent); outline-offset: 2px; }

@media (hover: hover) and (pointer: fine) {
  :is(.nav-close, .nav-search__close, .nav-search-trigger, .nav-global-search, .nav-tab, .nav-tools button, .nav-steps a, .nav-crumbs a, .nav-crumbs button):hover { color: var(--nav-ink); background: var(--nav-surface); text-decoration: none; }
  .rail :is(.entry, .tnode--sec, .twist--btn, .mod):hover { background: var(--nav-surface); }
  :is(.nav-resume, .nav-outline__link, .nav-outline__top, .nav-search__result):hover { color: var(--nav-ink); background: var(--nav-surface); text-decoration: none; }
}

@media (min-width: 941px) {
  #railtoggle .navbtn__ico--close { display: none; }
  #railtoggle .navbtn__ico--menu { opacity: 1; transform: none; transition: none; }
  #railtoggle[aria-expanded="true"] { color: var(--nav-accent); background: var(--nav-selected); }
}

@media (min-width: 941px) and (max-width: 1180px) {
  .nav-global-search { flex: none; width: 2.75rem; min-width: 2.75rem; padding: .625rem; margin-left: .5rem; justify-content: center; }
  .nav-global-search :is(span, kbd) { display: none; }
}

@media (max-width: 940px) {
  html[data-nav-open="true"] { overflow: hidden; }
  .nav-global-search { display: none; }
  .rail { width: min(100%, 25rem); padding: 0; padding-left: env(safe-area-inset-left, 0px); padding-bottom: env(safe-area-inset-bottom, 0px); background: var(--nav-canvas); }
  .nav-head { min-height: 3.5rem; padding: .375rem .75rem .375rem 1.25rem; }
  .nav-head h2 { font-size: 1.25rem; }
  .nav-close { display: inline-flex; }
  .nav-search-trigger { margin-bottom: .75rem; }
  .nav-search-trigger kbd { display: none; }
  .nav-tabs { margin-bottom: .75rem; }
  .nav-mobile {
    position: fixed;
    z-index: 55;
    inset: auto 0 0;
    display: grid;
    grid-template-columns: repeat(3, minmax(0, 1fr));
    min-height: var(--nav-dock-h);
    padding: .25rem max(.5rem, env(safe-area-inset-right, 0px)) max(.25rem, env(safe-area-inset-bottom, 0px)) max(.5rem, env(safe-area-inset-left, 0px));
    border-top: 1px solid var(--nav-line);
    color: var(--nav-ink);
    background: var(--nav-canvas);
  }
  .nav-mobile button { display: flex; flex-direction: column; align-items: center; justify-content: center; gap: .25rem; min-height: 3.5rem; min-width: 0; padding: .375rem .25rem; border-radius: .5rem; color: var(--nav-muted); font-size: .75rem; font-weight: 600; line-height: 1.3; }
  .nav-mobile button[aria-expanded="true"],
  .nav-mobile button[aria-current="true"] { color: var(--nav-accent); background: var(--nav-selected); }
  .nav-mobile button:disabled { opacity: .45; cursor: default; }
  .readerhud { bottom: calc(var(--nav-dock-h) + .75rem); }
  .main { padding-bottom: var(--nav-dock-h); }
  .nav-context { margin-bottom: 1rem; gap: .25rem .75rem; }
  .nav-search { width: calc(100% - 1rem); max-height: calc(100dvh - max(1rem, env(safe-area-inset-top, 0px)) - env(safe-area-inset-bottom, 0px)); border-radius: .75rem; }
  .nav-search__head { padding: .75rem 1rem .375rem; }
  .nav-search__inputwrap { margin: 0 1rem .75rem; }
  .nav-search__status { padding-inline: 1rem; }
  .nav-search__hint { padding: .625rem 1rem; }
}

@media (max-width: 599px) {
  .nav-context { align-items: stretch; }
  .nav-crumbs { width: 100%; }
  .nav-steps { margin-left: auto; }
  .nav-search__hint { display: none; }
}

@media (max-width: 940px) and (max-height: 560px) {
  .nav-header { display: grid; grid-template-columns: minmax(0, 1fr) 2.75rem; gap: 0 .5rem; padding: .5rem 1rem 0; }
  .nav-head { grid-column: 2; grid-row: 1; min-height: 2.75rem; padding: 0; }
  .nav-head h2 { display: none; }
  .nav-search-trigger { grid-column: 1; grid-row: 1; width: 100%; margin: 0; }
  .nav-tabs { grid-column: 1 / -1; margin: .5rem 0; }
  .nav-filter { flex-direction: row; align-items: center; gap: .5rem; }
  .nav-filter label { flex: none; }
  .nav-filter select { min-width: 0; flex: 1; }
  .nav-tools { padding-top: .25rem; padding-bottom: .25rem; }
  .nav-resume { display: none; }
  .rail .rail__foot { padding-block: .25rem; }
  .nav-search__head { padding-block: .25rem; }
  .nav-search__inputwrap { margin-bottom: .375rem; }
  .nav-search__input { min-height: 2.75rem; padding-block: .5rem; }
  .nav-search__status { padding-bottom: .375rem; }
  .nav-search__hint { display: none; }
}

@media (prefers-reduced-motion: reduce) {
  .rail, .rail *, .nav-mobile *, .nav-search * { scroll-behavior: auto; animation: none !important; transition: none !important; }
}