:root {
  --bg-dark: #161412;
  --bg-paper: #f3efe8;
  --bg-paper-strong: #ebe5dc;
  --bg-muted: #ddd5ca;
  --ink-strong: #171412;
  --ink-body: #463d35;
  --ink-soft: #7a6d61;
  --ink-on-dark: #f5f1ea;
  --line-strong: #1c1916;
  --line-soft: #b8afa3;
  --accent: #7c3327;
  --font-display: "Iowan Old Style", "Palatino Linotype", "Book Antiqua", Georgia, serif;
  --font-body: "Avenir Next", "Segoe UI", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  min-height: 100vh;
  color: var(--ink-strong);
  font-family: var(--font-body);
  background: var(--bg-paper);
}

body::before {
  content: "";
  position: fixed;
  inset: 0;
  pointer-events: none;
  background-image:
    linear-gradient(rgba(0, 0, 0, 0.05) 1px, transparent 1px),
    linear-gradient(90deg, rgba(0, 0, 0, 0.05) 1px, transparent 1px);
  background-size: 28px 28px;
  opacity: 0.18;
}

a {
  color: inherit;
}

#app {
  width: min(1180px, calc(100% - 32px));
  margin: 0 auto;
  padding: 24px 0 48px;
}

.page-shell {
  display: grid;
  gap: 20px;
}

.hero,
.language-panel,
.summary-card,
.toc,
.section-card {
  border: 1px solid var(--line-strong);
  border-radius: 0;
  box-shadow: none;
}

.hero {
  padding: 22px 24px;
  color: var(--ink-strong);
  background: var(--bg-paper);
}

.hero-flat {
  border-top-width: 2px;
}

.hero-grid {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 12px;
  align-items: end;
}

.brand-row {
  display: flex;
  align-items: center;
  gap: 10px;
  margin-bottom: 14px;
}

.brand-mark {
  width: 36px;
  height: 36px;
  padding: 6px;
  border: 1px solid var(--line-soft);
  background: transparent;
}

.brand-mark img {
  width: 100%;
  height: 100%;
  display: block;
}

.brand-copy {
  display: grid;
  gap: 3px;
}

.brand-copy strong {
  font-weight: 700;
  letter-spacing: 0.06em;
}

.brand-copy span {
  font-size: 0.82rem;
  color: var(--ink-soft);
}

.eyebrow {
  display: inline-block;
  padding: 2px 0 6px;
  border-bottom: 1px solid var(--line-soft);
  font-size: 0.72rem;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--ink-soft);
}

.hero h1 {
  margin: 12px 0 8px;
  max-width: 16ch;
  font-family: var(--font-display);
  font-size: clamp(1.8rem, 3vw, 2.8rem);
  line-height: 1.04;
  letter-spacing: -0.04em;
}

.hero p {
  margin: 0;
}

.hero-lede {
  max-width: 64ch;
  font-size: 0.95rem;
  line-height: 1.7;
  color: var(--ink-body);
}

.hero-note {
  margin-top: 10px;
  padding-top: 10px;
  border-top: 1px solid var(--line-soft);
  max-width: 60ch;
  font-size: 0.88rem;
  line-height: 1.62;
  color: var(--ink-soft);
}

.hero-aside {
  display: block;
}

.meta-inline {
  display: inline-flex;
  gap: 8px;
  align-items: center;
  padding-top: 2px;
  font-size: 0.82rem;
  color: var(--ink-soft);
}

.meta-inline-label {
  text-transform: uppercase;
  letter-spacing: 0.08em;
}

.meta-inline-value {
  color: var(--ink-body);
}

.language-panel,
.toc,
.section-card,
.summary-card {
  background: var(--bg-paper);
}

.language-panel,
.toc,
.section-card {
  padding: 24px;
}

.panel-heading {
  display: grid;
  gap: 6px;
  margin-bottom: 18px;
}

.panel-heading h2,
.summary-wrap h2,
.toc-title,
.section-card h2 {
  margin: 0;
  font-family: var(--font-display);
  letter-spacing: -0.03em;
}

.panel-heading h2,
.summary-wrap h2 {
  font-size: clamp(1.45rem, 2vw, 1.95rem);
}

.panel-heading p,
.summary-wrap p,
.toc-copy,
.section-card p,
.section-card li,
.footer-card p {
  margin: 0;
  line-height: 1.78;
  color: var(--ink-body);
}

.language-grid {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.lang-pill {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 42px;
  padding: 0 16px;
  text-decoration: none;
  border: 1px solid var(--line-soft);
  background: transparent;
  color: var(--ink-body);
  font-weight: 600;
  transition: background 160ms ease, color 160ms ease, border-color 160ms ease;
}

.lang-pill:hover,
.lang-pill:focus-visible {
  background: var(--bg-paper-strong);
  color: var(--ink-strong);
  border-color: var(--line-strong);
  outline: none;
}

.lang-pill.active {
  color: var(--ink-on-dark);
  background: var(--line-strong);
  border-color: var(--line-strong);
}

.summary-wrap {
  display: grid;
  gap: 16px;
}

.summary-grid {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 10px;
}

.summary-card {
  padding: 20px;
}

.summary-card strong {
  display: block;
  margin-bottom: 10px;
  font-size: 0.98rem;
}

.summary-card p {
  margin: 0;
  line-height: 1.72;
  color: var(--ink-body);
}

.content-grid {
  display: grid;
  grid-template-columns: minmax(250px, 280px) minmax(0, 1fr);
  gap: 18px;
  align-items: start;
}

.toc {
  position: sticky;
  top: 18px;
  background:
    linear-gradient(180deg, var(--bg-paper-strong), var(--bg-paper));
}

.toc-title {
  font-size: 1.45rem;
}

.toc-copy {
  margin: 8px 0 18px;
}

.toc-list {
  display: grid;
  gap: 0;
  border-top: 1px solid var(--line-soft);
}

.toc-list a {
  display: block;
  padding: 12px 0;
  text-decoration: none;
  color: var(--ink-body);
  border-bottom: 1px solid var(--line-soft);
}

.toc-list a:hover,
.toc-list a:focus-visible {
  color: var(--accent);
  outline: none;
}

.section-list {
  display: grid;
  gap: 10px;
}

.section-card {
  scroll-margin-top: 18px;
  background: var(--bg-paper);
}

.section-card h2 {
  margin-bottom: 16px;
  padding-bottom: 12px;
  font-size: clamp(1.45rem, 2.2vw, 1.95rem);
  border-bottom: 1px solid var(--line-soft);
}

.section-card p {
  margin-bottom: 14px;
}

.section-card p:last-child {
  margin-bottom: 0;
}

.section-card ul {
  margin: 4px 0 0;
  padding-left: 18px;
  color: var(--ink-body);
}

.section-card li {
  margin: 10px 0;
}

@media (max-width: 980px) {
  .hero-grid,
  .content-grid,
  .summary-grid {
    grid-template-columns: 1fr;
  }

  .toc {
    position: static;
  }
}

@media (max-width: 720px) {
  #app {
    width: min(100%, calc(100% - 18px));
    padding: 12px 0 28px;
  }

  .hero,
  .language-panel,
  .toc,
  .section-card,
  .summary-card {
    padding: 18px;
  }

  .hero h1 {
    max-width: none;
  }

  .lang-pill {
    width: calc(50% - 4px);
  }
}

@media (max-width: 520px) {
  .lang-pill {
    width: 100%;
  }
}