:root {
  --course-ink: #18212f;
  --course-muted: #59677a;
  --course-line: #dce3ea;
  --course-paper: #f8fafc;
  --course-link: #1559a6;
  --course-focus: #2878c7;
}

* { box-sizing: border-box; }
body { margin: 0; color: var(--course-ink); background: var(--course-paper); font-family: ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif; line-height: 1.65; }
.course-page { width: min(100% - 48px, 860px); margin: 0 auto; padding: 38px 0 64px; }
.course-breadcrumb { display: flex; flex-wrap: wrap; gap: 8px; margin-bottom: 30px; color: var(--course-muted); font-size: .9rem; }
.course-breadcrumb a, .course-footer a { color: inherit; }
.course-hero, .lesson-header, .catalog-header { border-bottom: 1px solid var(--course-line); padding-bottom: 28px; }
.course-eyebrow { margin: 0 0 8px; color: var(--course-link); font-size: .82rem; font-weight: 750; letter-spacing: .08em; text-transform: uppercase; }
.course-page h1, .course-page h2, .course-page h3 { color: var(--course-ink); line-height: 1.2; }
.course-page h1 { margin: 0; font-size: clamp(2rem, 5vw, 3.5rem); letter-spacing: -.035em; }
.course-page h2 { margin-top: 0; font-size: 1.3rem; }
.course-title-en { margin: 7px 0 0; color: var(--course-muted); font-family: ui-monospace, SFMono-Regular, Menlo, monospace; font-size: .9rem; }
.course-summary, .catalog-header > p:last-child { max-width: 65ch; color: var(--course-muted); font-size: 1.06rem; }
.course-meta { display: flex; flex-wrap: wrap; gap: 22px; margin: 26px 0 0; }
.course-meta div { min-width: 112px; }
.course-meta dt { color: var(--course-muted); font-size: .78rem; }
.course-meta dd { margin: 2px 0 0; font-weight: 700; }
.course-section, .catalog-section { margin-top: 46px; }
.lesson-list { display: grid; gap: 12px; margin: 0; padding: 0; list-style: none; }
.lesson-card, .course-card { display: flex; gap: 15px; border: 1px solid var(--course-line); background: #fff; color: inherit; text-decoration: none; }
.lesson-card { align-items: center; padding: 17px 18px; border-radius: 8px; }
.lesson-card:hover, .course-card:hover { border-color: #9cbce0; box-shadow: 0 8px 20px rgba(34, 74, 114, .08); }
.lesson-card__number { color: var(--course-link); font-family: ui-monospace, SFMono-Regular, Menlo, monospace; font-weight: 800; }
.lesson-card strong, .lesson-card small { display: block; }
.lesson-card small, .lesson-card__source { color: var(--course-muted); font-size: .84rem; }
.lesson-card__source { margin-left: auto; text-align: right; }
.lesson-content { font-family: Georgia, "Noto Serif SC", serif; font-size: 1.05rem; }
.course-visual { margin: 30px 0 36px; border: 1px solid var(--course-line); border-radius: 10px; overflow: hidden; background: #fff; }
.course-visual__scroll { max-width: 100%; overflow-x: auto; overscroll-behavior-inline: contain; scrollbar-color: #79a8d8 #edf5ff; }
.course-visual__scroll:focus-visible { outline: 3px solid var(--course-focus); outline-offset: -3px; }
.course-visual img { display: block; width: 100%; height: auto; }
.course-visual figcaption { padding: 12px 16px; border-top: 1px solid var(--course-line); color: var(--course-muted); font-size: .9rem; }
.course-visual__hint { display: none; margin-top: 3px; color: var(--course-link); font-size: .82rem; font-weight: 700; }
.lesson-content h1 { font-size: 2rem; }
.lesson-content h2 { margin-top: 2.2em; }
.lesson-content a { color: var(--course-link); }
.lesson-content pre, .lesson-content table { display: block; max-width: 100%; overflow-x: auto; }
.lesson-content pre { padding: 16px; border-radius: 6px; background: #18212f; color: #f7fbff; font-family: ui-monospace, SFMono-Regular, Menlo, monospace; font-size: .88rem; }
.lesson-content table { border-collapse: collapse; }
.lesson-content th, .lesson-content td { padding: 9px 12px; border: 1px solid var(--course-line); text-align: left; }
.lesson-pagination { display: flex; flex-wrap: wrap; justify-content: space-between; gap: 12px; margin-top: 40px; padding-top: 20px; border-top: 1px solid var(--course-line); }
.lesson-pagination a { color: var(--course-link); font-weight: 700; }
.source-disclosure { margin-top: 42px; padding: 20px 22px; border: 1px solid var(--course-line); border-radius: 8px; background: #fff; }
.source-disclosure h2 { margin-bottom: 10px; }
.source-disclosure p { margin: 7px 0; overflow-wrap: anywhere; color: var(--course-muted); }
.source-disclosure a { color: var(--course-link); }
.course-status { display: inline-flex; align-items: center; border-radius: 999px; padding: 3px 9px; font-size: .76rem; font-weight: 750; }
.course-status--available { background: #e3f6eb; color: #17663a; }
.course-status--coming-soon { background: #fff2d8; color: #8a5500; }
.course-grid, .legacy-course-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(250px, 1fr)); gap: 16px; }
.course-card { min-height: 216px; flex-direction: column; padding: 20px; border-radius: 8px; }
.course-card__top { display: flex; align-items: center; justify-content: space-between; gap: 12px; color: var(--course-muted); font-size: .82rem; }
.course-card > strong { font-size: 1.15rem; }
.course-card__title-en, .course-card__summary, .course-card__meta { color: var(--course-muted); }
.course-card__summary { font-size: .92rem; }
.course-card__meta { margin-top: auto; font-size: .82rem; }
.course-empty { color: var(--course-muted); }
.course-footer { padding: 22px; border-top: 1px solid var(--course-line); color: var(--course-muted); text-align: center; font-size: .8rem; }
.course-page a:focus-visible, .course-footer a:focus-visible { outline: 3px solid var(--course-focus); outline-offset: 3px; }

@media (max-width: 640px) {
  .course-page { width: min(100% - 28px, 860px); padding: 26px 0 44px; }
  .course-breadcrumb { margin-bottom: 22px; }
  .course-meta { gap: 14px; }
  .lesson-card { align-items: flex-start; flex-wrap: wrap; }
  .lesson-card__source { width: 100%; margin-left: 0; text-align: left; }
  .lesson-pagination { flex-direction: column; }
  .course-grid, .legacy-course-grid { grid-template-columns: 1fr; }
  .course-visual img { width: 960px; max-width: none; }
  .course-visual__hint { display: block; }
}

/* CHECKIN COURSE START */
.checkin-course {
  --checkin-focus: #005fcc;
  --checkin-accent: #185fa8;
  --checkin-soft: #edf5ff;
  --checkin-warning: #fff5d8;
  --checkin-warning-ink: #694300;
  width: min(100% - 48px, 1120px);
}

.checkin-course .checkin-hero { padding-bottom: 30px; border-bottom: 1px solid var(--course-line); }
.checkin-course .checkin-hero > :last-child { margin-bottom: 0; }
.checkin-course .checkin-facts { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 12px; margin: 28px 0 0; }
.checkin-course .checkin-facts div { min-width: 0; padding: 14px 16px; border: 1px solid var(--course-line); border-radius: 8px; background: #fff; }
.checkin-course .checkin-facts dt { color: var(--course-muted); font-size: .78rem; }
.checkin-course .checkin-facts dd { margin: 3px 0 0; font-weight: 750; }
.checkin-course .checkin-notice,
.checkin-course .checkin-progress-panel,
.checkin-course .checkin-disclosure { margin-top: 28px; padding: 20px 22px; border: 1px solid var(--course-line); border-radius: 9px; background: #fff; }
.checkin-course .checkin-notice { border-left: 5px solid var(--checkin-accent); }
.checkin-course .checkin-progress-panel { background: var(--checkin-soft); }
.checkin-course .checkin-disclosure { color: var(--course-muted); }
.checkin-course .checkin-notice h2,
.checkin-course .checkin-progress-panel h2,
.checkin-course .checkin-disclosure h2 { margin-bottom: 8px; }
.checkin-course .checkin-notice p,
.checkin-course .checkin-disclosure p { margin: 7px 0; }
.checkin-course .checkin-subnav,
.checkin-course .checkin-week-navigation { display: flex; flex-wrap: wrap; gap: 10px; margin-top: 28px; }
.checkin-course .checkin-subnav a,
.checkin-course .checkin-week-navigation a,
.checkin-course .checkin-primary-action { display: inline-flex; align-items: center; min-height: 44px; padding: 9px 14px; border: 1px solid #8db5dc; border-radius: 7px; background: #fff; color: var(--checkin-accent); font-weight: 720; text-decoration: none; }
.checkin-course .checkin-primary-action { margin-right: 10px; border-color: var(--checkin-accent); background: var(--checkin-accent); color: #fff; }
.checkin-course .checkin-section { margin-top: 44px; min-width: 0; }
.checkin-course .checkin-week-grid,
.checkin-course .knowledge-grid,
.checkin-course .checkin-outcome-grid { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 16px; }
.checkin-course .checkin-knowledge-stat-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(min(100%, 180px), 1fr)); gap: 12px; }
.checkin-course .checkin-knowledge-stat { display: flex; min-width: 0; min-height: 76px; flex-direction: column; justify-content: center; padding: 14px 16px; border: 1px solid #8db5dc; border-radius: 8px; background: #fff; color: var(--checkin-accent); text-decoration: none; overflow-wrap: anywhere; }
.checkin-course .checkin-knowledge-stat span { color: var(--course-muted); font-size: .86rem; }
.checkin-course .checkin-knowledge-search { margin: 28px 0; padding: 20px 22px; border: 1px solid var(--course-line); border-radius: 9px; background: #fff; }
.checkin-course .checkin-knowledge-search h2 { margin-bottom: 10px; }
.checkin-course .checkin-knowledge-search label { display: block; margin-bottom: 7px; font-weight: 720; }
.checkin-course .checkin-knowledge-search input { display: block; width: 100%; max-width: 42rem; min-height: 44px; padding: 9px 12px; border: 1px solid #6b7788; border-radius: 7px; background: #fff; color: var(--course-ink); font: inherit; }
.checkin-course .checkin-knowledge-search [data-knowledge-results] { margin-bottom: 0; color: var(--course-muted); }
.checkin-course .checkin-knowledge-empty { padding: 18px; border: 1px solid var(--course-line); border-radius: 8px; background: #fff; }
.checkin-course [hidden] { display: none; }
.checkin-course .checkin-week-card,
.checkin-course .knowledge-card,
.checkin-course .checkin-outcome-card,
.checkin-course .assessment-card,
.checkin-course .rubric-card { min-width: 0; padding: 20px; border: 1px solid var(--course-line); border-radius: 9px; background: #fff; overflow-wrap: anywhere; }
.checkin-course .checkin-week-card h3,
.checkin-course .knowledge-card h3,
.checkin-course .checkin-outcome-card h3,
.checkin-course .assessment-card h3 { margin: 5px 0 9px; }
.checkin-course .checkin-week-card a,
.checkin-course .knowledge-card a { color: var(--checkin-accent); }
.checkin-course .checkin-kicker { margin: 0; color: var(--course-muted); font-size: .78rem; font-weight: 750; letter-spacing: .04em; }
.checkin-course .checkin-week-progress { color: var(--checkin-accent); font-weight: 750; }
.checkin-course .checkin-incomplete { padding: 12px 14px; border-left: 4px solid #b47800; background: var(--checkin-warning); color: var(--checkin-warning-ink); }
.checkin-course .checkin-day-list,
.checkin-course .assessment-list,
.checkin-course .knowledge-groups { display: grid; gap: 24px; min-width: 0; }
.checkin-course .checkin-day-card { min-width: 0; padding: 26px; border: 1px solid var(--course-line); border-radius: 10px; background: #fff; overflow-wrap: anywhere; }
.checkin-course .checkin-day-card > header { padding-bottom: 18px; border-bottom: 1px solid var(--course-line); }
.checkin-course .checkin-day-card > section { margin-top: 24px; }
.checkin-course .checkin-audio-queue,
.checkin-course .checkin-day-media { margin-top: 28px; padding: 20px 22px; border: 1px solid var(--course-line); border-radius: 9px; background: #fff; }
.checkin-course .checkin-day-media-grid { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 16px; }
.checkin-course .checkin-day-media-grid > div { min-width: 0; padding: 16px; border-radius: 8px; background: var(--course-paper); }
.checkin-course .checkin-day-media audio,
.checkin-course .checkin-audio-now audio { display: block; width: 100%; margin-top: 12px; }
.checkin-course .checkin-audio-controls { display: flex; flex-wrap: wrap; align-items: end; gap: 10px; }
.checkin-course .checkin-audio-controls label { display: grid; gap: 4px; font-weight: 720; }
.checkin-course .checkin-audio-controls select { min-height: 44px; padding: 8px 10px; border: 1px solid #6b7788; border-radius: 7px; background: #fff; color: var(--course-ink); font: inherit; }
.checkin-course .checkin-video-cover { position: relative; width: 100%; aspect-ratio: 16 / 9; margin-top: 14px; overflow: hidden; border-radius: 8px; background: #000; }
.checkin-course .lv-play { position: absolute; inset: 0; display: block; width: 100%; height: 100%; padding: 0; border: 0; background: #000; cursor: pointer; }
.checkin-course .lv-play img { position: absolute; inset: 0; width: 100%; height: 100%; object-fit: cover; }
.checkin-course .lv-play__icon { position: absolute; left: 50%; top: 50%; transform: translate(-50%, -50%); width: 54px; height: 54px; line-height: 50px; border: 2px solid rgba(255,255,255,.85); border-radius: 50%; background: rgba(0,0,0,.55); color: #fff; font-size: 1.1rem; }
.checkin-course .lv-play:hover .lv-play__icon { background: rgba(47,95,208,.85); }
.checkin-course .lv-modal { position: fixed; inset: 0; z-index: 2147483000; display: flex; align-items: center; justify-content: center; padding: 1rem; background: rgba(0,0,0,.82); }
.checkin-course .lv-modal[hidden] { display: none; }
.checkin-course .lv-modal__box { display: flex; flex-direction: column; gap: .5rem; width: min(1100px,94vw); }
.checkin-course .lv-modal__bar { display: flex; align-items: center; justify-content: space-between; gap: 1rem; color: #fff; }
.checkin-course .lv-modal__title { display: -webkit-box; overflow: hidden; font-size: .95rem; line-height: 1.5; -webkit-line-clamp: 2; -webkit-box-orient: vertical; }
.checkin-course .lv-modal__tools { display: flex; flex-shrink: 0; align-items: center; gap: .75rem; }
.checkin-course .lv-modal__close { padding: .2rem .5rem; border: 0; background: none; color: #fff; font-size: 1.3rem; cursor: pointer; }
.checkin-course .lv-modal__full, .checkin-course .lv-modal__out { padding: .34rem .7rem; border: 0; border-radius: 5px; background: rgba(255,255,255,.14); color: #fff; font-size: .82rem; text-decoration: none; white-space: nowrap; cursor: pointer; }
.checkin-course .lv-modal__full:hover, .checkin-course .lv-modal__out:hover { background: rgba(255,255,255,.26); }
.checkin-course .lv-modal__frame { position: relative; overflow: hidden; aspect-ratio: 16 / 9; border-radius: 8px; background: #000; }
.checkin-course .lv-modal__frame iframe { position: absolute; inset: 0; width: 100%; height: 100%; border: 0; }
.checkin-course .lv-modal--max { padding: 0; }
.checkin-course .lv-modal--max .lv-modal__box { width: 100vw; max-width: none; height: 100dvh; gap: 0; }
.checkin-course .lv-modal--max .lv-modal__bar { padding: .5rem .75rem; background: #000; }
.checkin-course .lv-modal--max .lv-modal__frame { display: flex; flex: 1; align-items: center; justify-content: center; aspect-ratio: auto; border-radius: 0; }
.checkin-course .lv-modal--max .lv-modal__frame iframe { position: static; width: 100%; height: 100%; }
.checkin-course .checkin-media-state { color: var(--course-muted); }
.checkin-course .checkin-day-card h3 { margin: 4px 0 8px; font-size: 1.55rem; }
.checkin-course .checkin-day-card h4 { margin: 0 0 10px; font-size: 1.08rem; }
.checkin-course .checkin-day-card h5 { margin: 0 0 7px; font-size: .96rem; }
.checkin-course .checkin-day-card ul,
.checkin-course .knowledge-detail ul { padding-left: 1.25rem; }
.checkin-course .checkin-day-card li,
.checkin-course .knowledge-detail li { margin: 6px 0; }
.checkin-course .checkin-content-section { margin: 15px 0; padding: 14px 16px; border: 1px solid var(--course-line); border-radius: 7px; background: var(--course-paper); }
.checkin-course .checkin-level-grid { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 12px; }
.checkin-course .checkin-level-card { min-width: 0; padding: 14px; border: 1px solid var(--course-line); border-radius: 7px; background: var(--course-paper); overflow-wrap: anywhere; }
.checkin-course .checkin-level-card p { margin: 0; }
.checkin-course .co-badge,
.checkin-course .co-ref { display: inline-flex; align-items: center; border-radius: 999px; background: #dceeff; color: #0c4d87; font-size: .78rem; font-weight: 800; }
.checkin-course .co-badge { padding: 5px 10px; }
.checkin-course .co-ref { margin: 2px; padding: 2px 7px; }
.checkin-course .checkin-question { margin-top: 14px; padding: 16px; border: 1px solid var(--course-line); border-radius: 7px; background: var(--course-paper); }
.checkin-course .checkin-question details { margin-top: 10px; }
.checkin-course .checkin-question summary { color: var(--checkin-accent); cursor: pointer; font-weight: 720; }
.checkin-course .checkin-table-scroll { max-width: 100%; overflow-x: auto; overscroll-behavior-inline: contain; }
.checkin-course .checkin-table-scroll table { width: 100%; min-width: 720px; border-collapse: collapse; background: #fff; }
.checkin-course .checkin-table-scroll th,
.checkin-course .checkin-table-scroll td { padding: 11px 12px; border: 1px solid var(--course-line); text-align: left; vertical-align: top; }
.checkin-course .checkin-table-scroll th { background: var(--course-paper); }
.checkin-course .rubric-card { margin-top: 20px; }
.checkin-course button { min-height: 44px; max-width: 100%; margin-top: 16px; padding: 10px 15px; border: 1px solid var(--checkin-accent); border-radius: 7px; background: var(--checkin-accent); color: #fff; font: inherit; font-weight: 720; cursor: pointer; white-space: normal; }
.checkin-course button:disabled { border-color: #6b7788; background: #6b7788; cursor: not-allowed; }
.checkin-course a:focus-visible,
.checkin-course button:focus-visible,
.checkin-course input:focus-visible,
.checkin-course summary:focus-visible,
.checkin-course .checkin-table-scroll:focus-visible { outline: 3px solid #005fcc; outline-offset: 3px; }

@media (max-width: 640px) {
  .checkin-course { width: min(100% - 28px, 1120px); }
  .checkin-course .checkin-facts,
  .checkin-course .checkin-week-grid,
  .checkin-course .knowledge-grid,
  .checkin-course .checkin-outcome-grid,
  .checkin-course .checkin-level-grid { grid-template-columns: minmax(0, 1fr); }
  .checkin-course .checkin-day-media-grid { grid-template-columns: minmax(0, 1fr); }
  .checkin-course .checkin-day-card,
  .checkin-course .checkin-week-card,
  .checkin-course .knowledge-card,
  .checkin-course .checkin-outcome-card,
  .checkin-course .assessment-card,
  .checkin-course .rubric-card { padding: 18px; }
  .checkin-course .checkin-subnav,
  .checkin-course .checkin-week-navigation { flex-direction: column; }
  .checkin-course .checkin-subnav a,
  .checkin-course .checkin-week-navigation a,
  .checkin-course .checkin-primary-action,
  .checkin-course button { width: 100%; justify-content: center; margin-right: 0; }
}

@media (prefers-reduced-motion: reduce) {
  .checkin-course *,
  .checkin-course *::before,
  .checkin-course *::after { scroll-behavior: auto; transition-duration: 0.01ms; animation-duration: 0.01ms; animation-iteration-count: 1; }
}
/* CHECKIN COURSE END */

/* 知识卡技术演进时间轴：只增补不覆盖，因此按代次列出并折叠较早的几项。
   注意：courses.css 全文没有深色主题，页面在任何系统配色下都是浅色。
   这里若单独加 prefers-color-scheme 深色块，只有本组件会翻深、文字仍继承
   页面的深色前景，结果是深底深字。所以这里同样只写浅色。 */
.knowledge-timeline { margin: 0 0 1.6rem; }
.knowledge-timeline h3 { margin: 0 0 .3rem; font-size: 1.05rem; }
.knowledge-timeline-note {
  margin: 0 0 .7rem; font-size: .88rem; color: #5b6b66;
  border-left: 3px solid #cfe0da; padding-left: .7rem;
}
.knowledge-timeline-list { list-style: none; margin: 0; padding: 0; display: grid; gap: .4rem; }
.knowledge-timeline-item {
  display: grid; gap: .2rem .8rem; align-items: baseline;
  grid-template-columns: minmax(5.5rem, auto) auto auto;
  padding: .5rem .7rem; background: #f6f9f8; border: 1px solid #e3ebe8; border-radius: 4px;
}
.knowledge-timeline-label { font-weight: 700; }
.knowledge-timeline-state {
  font-size: .8rem; padding: .05rem .5rem; border-radius: 999px;
  background: #e2f0ec; color: #146b5b; justify-self: start;
}
.knowledge-timeline-state[data-timeline-state="路线图"] { background: #f2efe4; color: #7a6320; }
.knowledge-timeline-state[data-timeline-state="试产"] { background: #f7edda; color: #8a5a12; }
.knowledge-timeline-since { font-size: .85rem; color: #5b6b66; font-variant-numeric: tabular-nums; }
.knowledge-timeline-sources {
  grid-column: 1 / -1; font-size: .8rem; display: flex; flex-wrap: wrap; gap: .25rem .7rem;
}
.knowledge-timeline-date { color: #7b8b86; margin-left: .35rem; }
.knowledge-timeline-more { margin-top: .5rem; font-size: .9rem; }
.knowledge-timeline-more summary { cursor: pointer; color: #146b5b; }
.knowledge-timeline-more .knowledge-timeline-list { margin-top: .5rem; }

/* 课程目录栏：宽屏左侧常驻，窄屏折叠为可展开的目录。
   纯标记与 CSS，不跑脚本 —— 课程承诺的无 JavaScript 阅读模式下目录也要在。
   这里同样只写浅色，理由见上方时间轴样式的说明。 */
.checkin-layout,
.course-library-layout { width: min(100% - 48px, 1280px); margin: 0 auto; }
.checkin-layout > .course-page,
.course-library-layout > .course-page { width: auto; margin: 0; }
/* 窄屏默认就是单栏：目录是一个能收起的 <details>，正文拿全宽。
   两栏、sticky、隐藏 summary 这三件事只在下方宽屏媒体查询里做——以前这里还有
   一份无条件的副本，手机上于是既是两栏、又没有可点的开关，正文被挤成一条。 */

.checkin-rail { margin: 24px 0 0; }
.checkin-rail__summary {
  cursor: pointer; padding: 10px 14px; border: 1px solid var(--course-line);
  border-radius: 6px; font-weight: 700; color: var(--course-ink); list-style: none;
}
.checkin-rail__summary::-webkit-details-marker { display: none; }
.checkin-rail__summary::before { content: "☰ "; color: var(--course-muted); }
.checkin-rail[open] .checkin-rail__summary::before { content: "✕ "; }
.checkin-rail__summary:focus-visible { outline: 3px solid var(--course-focus); outline-offset: 3px; }

.checkin-rail__body {
  padding: 14px 0 4px;
  /* 窄屏上目录不该把正文推到屏幕外，超出就在目录内部滚动 */
  max-height: 52vh; overflow-y: auto; overscroll-behavior: contain;
}
.checkin-rail__title {
  margin: 14px 0 6px; font-size: .74rem; font-weight: 750; letter-spacing: .09em;
  text-transform: uppercase; color: var(--course-muted);
}
.checkin-rail__title:first-child { margin-top: 0; }
.checkin-rail__body ul { list-style: none; margin: 0; padding: 0; display: grid; gap: 1px; }
.checkin-rail__body li a {
  display: block; padding: 6px 10px; border-radius: 5px; font-size: .9rem;
  color: var(--course-ink); text-decoration: none; line-height: 1.45;
}
.checkin-rail__body li a:hover { background: #eef4fb; }
.checkin-rail__body li a[aria-current="page"] {
  background: #e6f0fa; color: var(--course-link); font-weight: 700;
}
.checkin-rail__course-group { border-bottom: 1px solid var(--course-line); }
.checkin-rail__course-group > summary {
  padding: 10px 8px; color: var(--course-ink); font-weight: 750;
  cursor: pointer; list-style: none;
}
.checkin-rail__course-group > summary::-webkit-details-marker { display: none; }
.checkin-rail__course-group > summary::after { content: " ›"; color: var(--course-muted); }
.checkin-rail__course-group[open] > summary { color: var(--course-link); }
.checkin-rail__course-group[open] > summary::after { content: " ⌄"; }
.checkin-rail__course-group > ul { padding: 0 0 8px; }
/* 篇目页的听书区块。ready 给播放器，其余状态直接说明原因。 */
.lesson-media { margin: 0 0 22px; padding: 14px 16px; border: 1px solid var(--course-line); border-radius: 10px; background: var(--course-soft, #f7f9fb); }
.lesson-media h2 { margin: 0 0 10px; font-size: .95rem; font-weight: 750; }
.lesson-media audio { width: 100%; }
.lesson-media__meta { margin: 8px 0 0; color: var(--course-muted); font-size: .8rem; }
.lesson-media__state { margin: 0; color: var(--course-muted); font-size: .85rem; }
.lesson-media__state + .lesson-media__state { margin-top: 6px; }

/* 当前课程的篇目，缩进挂在课名下面，和 112 天课的日课列表用同一套视觉。 */
.checkin-rail__lessons { margin: 2px 0 8px; padding: 0 0 0 10px; border-left: 2px solid var(--course-line); }
.checkin-rail__lessons li a { display: grid; grid-template-columns: 22px minmax(0,1fr); align-items: baseline; gap: 8px; padding: 6px 8px; font-size: .82rem; }
.checkin-rail__lessons li a span { color: var(--course-muted); font-variant-numeric: tabular-nums; font-size: .74rem; }
.checkin-rail__lessons li a strong { font-weight: 550; }
.checkin-rail__lessons li a[aria-current="page"] { border-left: 3px solid var(--course-link); border-radius: 0 5px 5px 0; color: var(--course-link); }
.checkin-rail__lessons li a[aria-current="page"] strong { font-weight: 750; }
.checkin-rail__anchors li a { color: var(--course-muted); font-size: .86rem; }
.checkin-rail__anchors li a:hover { color: var(--course-ink); }
.checkin-rail__weeks li a { font-size: .86rem; }
.checkin-rail__categories { display: grid; gap: 3px; }
.checkin-rail__category { border-bottom: 1px solid var(--course-line); }
.checkin-rail__category > summary { display: flex; align-items: baseline; justify-content: space-between; gap: 8px; padding: 10px 8px; color: var(--course-ink); font-weight: 750; cursor: pointer; list-style: none; }
.checkin-rail__category > summary::-webkit-details-marker { display: none; }
.checkin-rail__category > summary::after { content: "›"; color: var(--course-muted); }
.checkin-rail__category[open] > summary { color: var(--course-link); }
.checkin-rail__category[open] > summary::after { content: "⌄"; }
.checkin-rail__category > summary small { margin-left: auto; color: var(--course-muted); font-size: .72rem; font-weight: 550; white-space: nowrap; }
.checkin-rail__category ul { max-height: 52vh; overflow-y: auto; padding: 2px 0 9px; }
.checkin-rail__category li a { display: grid; grid-template-columns: 12px 48px minmax(0,1fr); align-items: center; gap: 6px; padding: 7px 8px; font-size: .82rem; }
.checkin-rail__category li a strong { overflow: hidden; font-weight: 550; text-overflow: ellipsis; white-space: nowrap; }
.checkin-rail__state { width: 9px; height: 9px; border: 1px solid #aebbc8; border-radius: 50%; }
.checkin-rail__category li a[aria-current="page"] { border-left: 3px solid var(--course-link); border-radius: 0 5px 5px 0; }
.checkin-rail__category li a[aria-current="page"] .checkin-rail__state { border-color: var(--course-link); background: var(--course-link); }
.checkin-week[data-course-reader] > .checkin-hero,
.checkin-week[data-course-reader] > .checkin-week-navigation,
.checkin-week[data-course-reader] > .checkin-reader-days > h2 { display: none; }
.checkin-week[data-course-reader] > .checkin-reader-days { margin-top: 18px; padding: 0; border: 0; background: transparent; }
.checkin-week[data-course-reader] > .checkin-reader-days > .checkin-day-list { gap: 0; }
.checkin-week[data-course-reader] .checkin-day-card { padding: 0; border: 0; background: transparent; }


@media (min-width: 641px), (hover: hover) and (pointer: fine) {
  .checkin-layout,
  .course-library-layout {
    display: grid;
    grid-template-columns: clamp(240px, 26vw, 300px) minmax(0, 1fr);
    gap: clamp(24px, 3vw, 44px);
    align-items: start;
  }
  /* 宽屏上它就是一根固定的栏，不需要折叠控件 */
  .checkin-rail { position: sticky; top: 24px; margin: 38px 0 0; }
  .checkin-rail__summary { display: none; }
  .checkin-rail__body {
    padding: 0; max-height: calc(100vh - 72px); overflow-y: auto;
    border-right: 1px solid var(--course-line); padding-right: 14px;
  }

  /* 旧课程页的目录在宽屏上是常驻浮层。窄屏不能这么做：fixed 浮层会压住正文，
     正文那条 margin-left 也会把内容推出屏幕，所以整组收在这个条件里。 */
  body[data-course-library-page] > .checkin-rail {
    position: fixed; z-index: 20; top: 74px; bottom: 20px; left: 24px;
    width: clamp(240px, 26vw, 300px); margin: 0; padding: 14px; overflow: hidden;
    border: 1px solid var(--course-line); border-radius: 8px; background: #fff;
  }
  body[data-course-library-page] > .checkin-rail .checkin-rail__body {
    max-height: calc(100vh - 118px); border-right: 0; padding: 0; overflow-y: auto;
  }
  body[data-course-library-page] > .course-library-legacy-content {
    min-width: 0; margin-left: clamp(264px, calc(26vw + 24px), 324px);
  }
}