/* 导航沿用学习站的纸张与墨色；页边目录、题号和关联入口负责定位。 */
:root { --side-w: 278px; --top-h: 68px; --reading-h: 62px; --focus: #1d4ed8; }
html { scroll-behavior: auto; scroll-padding-top: calc(var(--top-h) + var(--reading-h) + 16px); }
[hidden] { display: none !important; }
.sr-only { position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px; overflow: hidden; clip: rect(0,0,0,0); white-space: nowrap; border: 0; }
a { text-underline-offset: 3px; }
:where(a, button, input, select, summary):focus-visible { outline: 2px solid var(--focus); outline-offset: 3px; }
button, select { font: inherit; }
button { cursor: pointer; }
.topbar { height: auto; min-height: 68px; gap: 24px; padding: 12px 24px; }
.brand { text-decoration: none; color: var(--ink); font-size: 18px; letter-spacing: .03em; }
.brand span { color: var(--accent); margin-left: 6px; font-family: var(--mono); }
.board-nav { background: transparent; padding: 0; gap: 5px; }
.board-nav a { padding: 6px 19px; color: var(--muted); text-decoration: none; border-radius: 8px; font-weight: 600; white-space: nowrap; }
.board-nav a.active { color: var(--accent); background: var(--accent-soft); box-shadow: inset 0 -2px 0 var(--accent); }
.board-nav a:hover { background: var(--accent-soft); }
.search-wrap { margin-left: auto; width: min(460px, 43vw); min-width: 200px; }
.search-wrap input { padding-right: 88px; font-size: 14px; }
.search-shortcut { position: absolute; right: 10px; top: 11px; font: 10px var(--mono); color: var(--muted); pointer-events: none; }
.search-results { width: min(560px, calc(100vw - 32px)); max-height: min(620px, 70vh); }
.search-results a { display: block; text-decoration: none; color: var(--ink); padding: 11px 16px; font-size: 14px; border-bottom: 1px solid var(--line); }
.search-results a:hover, .search-results a[aria-selected="true"] { background: var(--accent-soft); }
.search-group { position: sticky; top: 0; padding: 7px 16px; font-size: 12px; font-weight: 700; background: var(--paper); color: var(--accent); border-bottom: 1px solid var(--line); }
.search-excerpt { display: block; color: var(--muted); font-size: 12px; line-height: 1.6; margin-top: 4px; }
.search-empty { padding: 18px; color: var(--muted); font-size: 14px; }
.sidebar { padding: 18px 14px 40px; overscroll-behavior: contain; scrollbar-width: thin; }
.sidebar-heading { display: flex; justify-content: space-between; align-items: center; padding: 0 10px 14px; color: var(--muted); font-size: 12px; }
.nav-group { padding: 18px 10px 6px; font-size: 11px; font-weight: 600; color: var(--muted); letter-spacing: .08em; }
.nav-group:first-child { padding-top: 0; }
.side-nav .module-link { padding: 8px 12px; font-size: 14px; font-weight: 500; }
.nav-module.current > .module-link { background: var(--accent-soft); color: var(--accent); font-weight: 700; }
.module-toc { margin: 8px 0 12px 13px; border-left: 1px solid var(--line); padding-left: 8px; }
.toc-section { font-size: 11px; color: var(--muted); padding: 10px 8px 4px; }
.side-nav .toc-link { font-size: 12px; padding: 5px 8px; line-height: 1.6; border-radius: 4px; }
.side-nav .toc-link.active { background: transparent; color: var(--accent); box-shadow: -9px 0 0 -7px var(--accent); font-weight: 700; }
.layout { width: 100%; max-width: 1600px; margin-inline: auto; grid-template-columns: var(--side-w) minmax(0, 1fr); }
.main, body.fig-wide .main { padding-top: 0; max-width: none; }
.reading-rail { display: none; }
.reading-bar { position: sticky; top: var(--top-h); z-index: 25; padding: 13px 0; margin-bottom: 20px; background: var(--bg); border-bottom: 1px solid var(--line); }
.reading-location { min-height: 32px; display: flex; align-items: center; gap: 14px; flex-wrap: wrap; }
#breadcrumbs { display: flex; align-items: center; flex-wrap: wrap; gap: 6px; min-width: 0; font-size: 12px; color: var(--muted); }
#breadcrumbs a { color: var(--muted); text-decoration: none; }
#breadcrumbs a:hover { color: var(--accent); text-decoration: underline; }
#breadcrumbs [aria-current] { color: var(--ink); max-width: 28em; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.crumb-separator { color: #b7a891; }
#returnLink { background: var(--paper); border: 1px solid var(--line); color: var(--accent); border-radius: 6px; padding: 4px 8px; font-size: 12px; max-width: 100%; overflow: hidden; white-space: nowrap; text-overflow: ellipsis; }
.navigation-notice { padding: 10px 14px; background: var(--accent-soft); color: var(--ink); border-radius: 8px; font-size: 13px; }
.loading-message { padding: 30px 0; color: var(--muted); }
#examControls { display: flex; align-items: center; gap: 14px; padding-top: 10px; font-size: 13px; }
.year-select { display: flex; align-items: center; gap: 8px; color: var(--muted); }
.year-select select { border: 1px solid var(--line); padding: 5px 10px; border-radius: 6px; background: var(--paper); color: var(--ink); }
.current-question { color: var(--muted); font-variant-numeric: tabular-nums; }
.question-picker { position: relative; margin-left: auto; }
.question-picker summary { cursor: pointer; color: var(--accent); background: var(--paper); padding: 5px 10px; border: 1px solid var(--line); border-radius: 6px; }
.question-grid { position: absolute; right: 0; top: calc(100% + 8px); display: grid; grid-template-columns: repeat(5, 1fr); gap: 6px; width: 258px; max-height: 55vh; overflow: auto; padding: 14px; border: 1px solid var(--line); background: var(--paper); border-radius: 10px; box-shadow: var(--shadow); }
.question-grid a { text-align: center; padding: 7px 0; color: var(--ink); text-decoration: none; background: #f5efe4; border-radius: 5px; font-family: var(--mono); }
.question-grid a.active, .question-grid a:hover { background: var(--accent); color: white; }
.exam-question, .content-card[id], .formula-card[id], .exam-question-group { scroll-margin-top: calc(var(--top-h) + var(--reading-h) + 16px); }
.related-links { display: flex; flex-wrap: wrap; align-items: flex-start; gap: 8px; margin: 10px 0 18px; font-size: 12px; }
.related-links > a, .related-menu summary { display: inline-block; color: var(--accent); text-decoration: none; background: var(--accent-soft); border: 1px solid var(--line); border-radius: 6px; padding: 5px 9px; cursor: pointer; }
.related-links a:hover { text-decoration: underline; }
.related-menu { max-width: 100%; }
.related-menu summary { display: list-item; list-style-position: inside; }
.related-menu summary span { margin-left: 4px; font-family: var(--mono); }
.related-menu > div { display: grid; gap: 5px; padding: 10px; max-width: 380px; border-left: 2px solid var(--line); margin-top: 5px; }
.related-menu a { color: var(--accent); }
.exam-question > .related-links { margin-top: 18px; }
.exam-group-link { margin-left: auto; color: var(--accent); font-size: 12px; }
.question-pagination { display: flex; justify-content: space-between; gap: 12px; padding: 16px 0; font-size: 12px; }
.question-pagination a { color: var(--accent); text-decoration: none; }
.question-pagination a:hover { text-decoration: underline; }
.question-pagination span { color: var(--muted); }
.exam-table-scroll { overflow-x: auto; max-width: 100%; }
.exam-table a { color: var(--accent); }
.index-filters { display: flex; align-items: end; flex-wrap: wrap; gap: 12px; margin-bottom: 16px; }
.index-filters label { display: grid; gap: 5px; font-size: 12px; color: var(--muted); max-width: 100%; }
.index-filters select { border: 1px solid var(--line); border-radius: 6px; padding: 8px; background: var(--paper); color: var(--ink); min-width: 125px; max-width: 100%; font-size: 13px; }
.index-filters button { border: 0; color: var(--accent); background: transparent; padding: 8px; font-size: 13px; }
.filter-count { font-size: 13px; color: var(--muted); }
.menu-toggle, .menu-close, .drawer-backdrop { display: none; }
/* 宽屏把页边留白留给关联内容；主栏随容器伸展，外侧留白保持对称。 */
@media (min-width: 1360px) {
  :root { --side-w: 248px; }
  .layout { grid-template-columns: var(--side-w) minmax(0, 1fr) 240px; }
  .reading-rail { display: block; position: sticky; top: calc(var(--top-h) + 22px); align-self: start; max-height: calc(100dvh - var(--top-h) - 44px); overflow-y: auto; overscroll-behavior: contain; scrollbar-width: thin; margin-top: 22px; padding: 0 22px 18px 18px; border-left: 1px solid var(--line); }
  .rail-current { padding-bottom: 18px; }
  .rail-eyebrow { display: flex; align-items: center; justify-content: space-between; gap: 8px; color: var(--muted); font-size: 11px; }
  .rail-eyebrow > span { font-variant-numeric: tabular-nums; }
  .rail-current h2 { margin: 10px 0 6px; font-size: 17px; line-height: 1.5; font-weight: 650; overflow-wrap: anywhere; }
  .rail-location { margin: 0; color: var(--muted); font-size: 12px; }
  .rail-meta { display: flex; gap: 6px; margin-top: 10px; }
  .rail-meta span { padding: 1px 6px; font-size: 11px; border-radius: 4px; color: var(--accent); background: var(--accent-soft); }
  .rail-section { padding: 16px 0; border-top: 1px solid var(--line); }
  .rail-section h3 { display: flex; justify-content: space-between; align-items: center; gap: 6px; margin: 0 0 8px; font-size: 12px; font-weight: 650; }
  .rail-section h3 > span { color: var(--muted); font-weight: 400; font-size: 11px; }
  .rail-link { display: block; padding: 8px 0; font-size: 13px; color: var(--ink); text-decoration: none; overflow-wrap: anywhere; }
  .rail-link:hover { color: var(--accent); }
  .rail-link-meta { display: block; margin-top: 3px; color: var(--muted); font-size: 11px; line-height: 1.6; }
  .rail-exam-link { font-variant-numeric: tabular-nums; }
  .rail-more summary { padding-top: 8px; color: var(--accent); font-size: 12px; cursor: pointer; }
  .rail-question-grid { display: grid; grid-template-columns: repeat(5, minmax(0, 1fr)); gap: 5px; padding-top: 4px; }
  .rail-question-grid a { padding: 5px 0; border: 1px solid var(--line); border-radius: 5px; color: var(--muted); background: var(--paper); text-align: center; text-decoration: none; font: 12px/1.8 var(--mono); }
  .rail-question-grid a[aria-current], .rail-question-grid a:hover { background: var(--accent-soft); border-color: var(--accent); color: var(--accent); }
  .rail-neighbors { display: grid; gap: 8px; padding-top: 16px; border-top: 1px solid var(--line); }
  .rail-neighbors a { font-size: 12px; color: var(--accent); text-decoration: none; padding-block: 4px; overflow-wrap: anywhere; }
  .rail-neighbors a:hover { text-decoration: underline; }
  .rail-next { text-align: right; }
}
/* 图解、写作需要足够的图面和对照空间；超宽屏再显示第三栏。 */
body.index-view .layout { grid-template-columns: var(--side-w) minmax(0, 1fr); }
body.index-view .reading-rail { display: none; }
@media (min-width: 861px) and (max-width: 1759px) {
  body.wide-reading .layout { grid-template-columns: var(--side-w) minmax(0, 1fr); }
  body.wide-reading .reading-rail { display: none; }
}
@media (min-width: 1760px) {
  body.wide-reading .layout { max-width: 1800px; grid-template-columns: var(--side-w) minmax(0, 1fr) 240px; }
}
@media (min-width: 861px) and (max-width: 1100px) {
  :root { --side-w: 235px; }
  .topbar { gap: 14px; padding-inline: 18px; }
  .board-nav a { padding-inline: 12px; }
  .search-wrap { width: min(390px, 40vw); }
  .search-shortcut { display: none; }
  .search-wrap input { padding-right: 12px; }
  .main { padding-inline: 20px; }
}
@media (max-width: 860px) {
  :root { --top-h: 116px; }
  .layout, body.index-view .layout { grid-template-columns: minmax(0, 1fr); }
  .topbar { padding: 10px 16px; gap: 8px; flex-wrap: wrap; }
  .brand { font-size: 16px; }
  .board-nav { margin-left: auto; }
  .board-nav a { padding: 5px 12px; font-size: 14px; }
  .menu-toggle, .menu-close { display: inline-block; padding: 5px 9px; border: 1px solid var(--line); border-radius: 6px; background: var(--paper); color: var(--accent); font-size: 12px; }
  .search-wrap { width: 100%; min-width: 0; margin: 0; }
  .search-wrap input { font-size: 14px; }
  .search-results { width: 100%; max-height: 60vh; }
  .sidebar { position: fixed; top: 0; bottom: 0; left: 0; z-index: 70; width: min(330px, 86vw); height: 100dvh; max-height: none; background: var(--paper); visibility: hidden; transform: translateX(-100%); }
  .drawer-open { overflow: hidden; }
  .drawer-open .sidebar { visibility: visible; transform: none; }
  .drawer-backdrop:not([hidden]) { display: block; position: fixed; inset: 0; z-index: 60; background: rgba(31,26,20,.3); border: 0; }
  .main { padding-top: 0; }
  .reading-bar { padding-block: 9px; }
  .reading-location { gap: 7px; }
  #examControls { gap: 8px; font-size: 12px; }
  .year-select { gap: 5px; }
  .year-select select { padding: 5px; }
  .content-card { padding: 18px 16px; }
  .current-question { font-size: 11px; }
}
@media (max-width: 390px) {
  .brand { font-size: 14px; }
  .brand span { margin-left: 3px; }
  .board-nav a { padding-inline: 8px; }
  .current-question { display: none; }
  #breadcrumbs [aria-current] { max-width: 18em; }
}
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { scroll-behavior: auto !important; transition: none !important; animation: none !important; }
}
@media print {
  .reading-bar, .reading-rail, .related-links, .question-pagination, .exam-group-link, .index-filters, .navigation-notice, .drawer-backdrop { display: none !important; }
  .layout, body.index-view .layout, body.wide-reading .layout { max-width: none; grid-template-columns: 1fr; }
  .main, body.fig-wide .main { padding: 0; }
}