:root {
  --bg: #f6f4ef;
  --paper: #fffaf0;
  --ink: #1d2430;
  --muted: #667085;
  --line: #e6decf;
  --accent: #b23b2e;
  --accent-soft: #fff0ea;
  --blue: #244e8c;
  --green: #2f6b4f;
  --shadow: 0 12px 40px rgba(55, 43, 26, 0.10);
}

* { box-sizing: border-box; }

body {
  margin: 0;
  font-family: "Microsoft YaHei", "PingFang SC", "Noto Sans CJK SC", system-ui, sans-serif;
  color: var(--ink);
  background: radial-gradient(circle at top left, #fff3df 0, #f6f4ef 38rem);
  line-height: 1.72;
}

html { scroll-behavior: smooth; }

a { color: var(--blue); text-decoration: none; }
a:hover { text-decoration: underline; }

.topbar {
  position: sticky;
  top: 0;
  z-index: 10;
  display: flex;
  justify-content: space-between;
  gap: 1rem;
  padding: 0.75rem 1.5rem;
  background: rgba(255, 250, 240, 0.92);
  border-bottom: 1px solid var(--line);
  backdrop-filter: blur(10px);
}

.course-topbar {
  position: sticky;
  top: 0;
  z-index: 20;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  padding: 0.8rem max(1.25rem, calc((100vw - 1180px) / 2 + 1.25rem));
  color: #5f5142;
  background: rgba(255, 250, 240, 0.94);
  border-bottom: 1px solid var(--line);
  backdrop-filter: blur(12px);
}

.course-topbar span {
  color: var(--muted);
  font-size: 0.86rem;
}

.home-link {
  font-weight: 700;
}

.page, .index {
  max-width: 1180px;
  margin: 0 auto;
  padding: 2rem 1.25rem 4rem;
}

.hero, .index-hero, .note-section, .source-section, .all-images, .pdf-intro, .pdf-page {
  background: rgba(255, 250, 240, 0.92);
  border: 1px solid var(--line);
  border-radius: 22px;
  box-shadow: var(--shadow);
  padding: 1.5rem;
  margin: 1.25rem 0;
}

.eyebrow {
  color: var(--accent);
  letter-spacing: 0.08em;
  text-transform: uppercase;
  font-size: 0.82rem;
  margin: 0 0 0.25rem;
}

h1 {
  font-size: clamp(2rem, 5vw, 4rem);
  line-height: 1.08;
  margin: 0.2rem 0 1rem;
}

.lead {
  max-width: 900px;
  color: #394150;
  font-size: 1.05rem;
}

h2, h3, h4 {
  scroll-margin-top: 5rem;
  line-height: 1.25;
}

h2 {
  margin-top: 2.2rem;
  padding-bottom: 0.45rem;
  border-bottom: 2px solid var(--line);
}

h2 small, h3 small, h4 small {
  display: block;
  margin-top: 0.35rem;
  color: var(--muted);
  font-size: 0.86rem;
  font-weight: 500;
}

.source, .muted {
  color: var(--muted);
}

.notice {
  border-left: 5px solid var(--accent);
  background: var(--accent-soft);
  padding: 1rem 1.1rem;
  border-radius: 14px;
}

.note-content {
  background: white;
  border: 1px solid var(--line);
  border-radius: 16px;
  padding: 1rem 1.15rem;
}

.note-content img {
  max-width: 100%;
  height: auto;
  border-radius: 12px;
  border: 1px solid var(--line);
}

.sentence-card {
  display: grid;
  gap: 0.65rem;
  padding: 1rem;
  margin: 0.85rem 0;
  background: #fff;
  border: 1px solid var(--line);
  border-radius: 16px;
}

.sentence-card > div {
  padding-left: 0.8rem;
  border-left: 3px solid #ded4c2;
}

.sentence-card span {
  display: inline-block;
  min-width: 5.6rem;
  margin-right: 0.4rem;
  color: var(--muted);
  font-size: 0.82rem;
  font-weight: 700;
}

.sentence-card .en { color: #232323; }
.sentence-card .zh { border-left-color: var(--blue); color: #18345b; }
.sentence-card .note { border-left-color: var(--green); color: #234938; }

.list-cards {
  margin: 1rem 0;
  padding: 0.25rem 1rem;
  border-radius: 18px;
  background: #faf3e7;
  border: 1px dashed var(--line);
}

.figure-card {
  margin: 1.5rem auto;
  padding: 1rem;
  background: #fff;
  border: 1px solid var(--line);
  border-radius: 18px;
  text-align: center;
}

.figure-card img, .pdf-page img {
  max-width: 100%;
  height: auto;
  border-radius: 12px;
  border: 1px solid var(--line);
  background: white;
}

.figure-card figcaption {
  margin-top: 0.75rem;
  color: var(--muted);
  font-size: 0.95rem;
}

.figure-card figcaption span {
  color: var(--blue);
}

.table-wrap {
  overflow-x: auto;
  margin: 1rem 0;
}

table {
  width: 100%;
  border-collapse: collapse;
  background: white;
}

th, td {
  border: 1px solid var(--line);
  padding: 0.55rem 0.7rem;
  vertical-align: top;
}

th { background: #f5ead8; }

.gallery {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(180px, 1fr));
  gap: 1rem;
}

.gallery figure {
  margin: 0;
  padding: 0.75rem;
  background: white;
  border: 1px solid var(--line);
  border-radius: 14px;
}

.gallery img {
  width: 100%;
  height: 130px;
  object-fit: contain;
}

.gallery figcaption {
  color: var(--muted);
  font-size: 0.78rem;
  overflow-wrap: anywhere;
}

.pdf-page {
  background: #fffdf8;
}

.pdf-page h3 {
  margin-top: 0;
}

.pdf-text {
  margin-top: 1rem;
  padding: 0.75rem 1rem;
  background: #f8f4ec;
  border-radius: 14px;
  border: 1px solid var(--line);
}

.cards {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
  gap: 1rem;
  margin-top: 1.25rem;
}

.chapter-card {
  display: flex;
  flex-direction: column;
  min-height: 160px;
  padding: 1rem;
  border-radius: 18px;
  border: 1px solid var(--line);
  background: rgba(255, 250, 240, 0.95);
  box-shadow: var(--shadow);
}

.chapter-card strong {
  font-size: 1.08rem;
  line-height: 1.35;
}

.chapter-card span {
  margin-top: 0.5rem;
  color: var(--muted);
  font-size: 0.9rem;
}

.chapter-card em {
  margin-top: auto;
  color: var(--accent);
  font-style: normal;
  font-size: 0.85rem;
}

.stats {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
  margin: 1rem 0;
}

.stats span {
  padding: 0.45rem 0.75rem;
  background: white;
  border: 1px solid var(--line);
  border-radius: 999px;
}

.learning-path {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 0.8rem;
  margin: 1.5rem 0;
}

.learning-path a {
  display: flex;
  min-height: 132px;
  flex-direction: column;
  padding: 1rem;
  color: var(--ink);
  background: linear-gradient(145deg, #fff, #fff6e7);
  border: 1px solid var(--line);
  border-radius: 16px;
  transition: transform 180ms ease, border-color 180ms ease, box-shadow 180ms ease;
}

.learning-path a:hover {
  transform: translateY(-3px);
  border-color: #d5a99f;
  box-shadow: 0 12px 28px rgba(55, 43, 26, 0.12);
  text-decoration: none;
}

.learning-path small {
  color: var(--accent);
  font-weight: 700;
  letter-spacing: 0.05em;
}

.learning-path strong {
  margin-top: 0.2rem;
  font-size: 1.05rem;
}

.learning-path em {
  margin-top: auto;
  color: var(--blue);
  font-size: 0.84rem;
  font-style: normal;
}

.catalog-title {
  margin: 2rem 0 0;
}

.missing-image {
  color: #9a3412;
  background: #fff7ed;
  border: 1px solid #fed7aa;
  padding: 0.75rem;
  border-radius: 12px;
}

@media (max-width: 720px) {
  .topbar { position: static; flex-direction: column; }
  .course-topbar { position: static; padding: 0.75rem 1rem; }
  .course-topbar span { display: none; }
  .learning-path { grid-template-columns: 1fr; }
  .page, .index { padding: 1rem 0.75rem 3rem; }
  .hero, .index-hero, .note-section, .source-section, .all-images, .pdf-intro, .pdf-page { padding: 1rem; }
  .sentence-card span { display: block; margin-bottom: 0.15rem; }
}