:root {
  --color-bg: #fcfdfa;
  --color-paper: #fcfdfa;
  --color-ink: #1c1917;
  --color-ink-muted: #57534e;
  --color-ink-light: #78716c;
  --color-border: rgba(0, 0, 0, 0.08);
  --color-card: rgba(255, 255, 255, 0.72);
  --header-h: 72px;
  --max-w: 1180px;
  --font-serif: "Noto Serif SC", "Songti SC", "STSong", serif;
  --font-sans: "PingFang SC", "Microsoft YaHei", sans-serif;
}

* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  scroll-behavior: smooth;
}

body {
  font-family: var(--font-sans);
  color: var(--color-ink);
  background: var(--color-bg);
  line-height: 1.7;
  font-size: 16px;
}

a {
  color: inherit;
  text-decoration: none;
  transition: opacity 0.2s;
}

a:hover {
  opacity: 0.75;
}

img {
  max-width: 100%;
  display: block;
}

.container {
  width: min(100% - 48px, var(--max-w));
  margin: 0 auto;
}

/* ---------- Header ---------- */
.site-header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 100;
  height: var(--header-h);
  background: rgba(252, 253, 250, 0.88);
  backdrop-filter: blur(14px);
  border-bottom: 1px solid transparent;
  transition: border-color 0.25s, box-shadow 0.25s;
}

.site-header.is-scrolled {
  border-bottom-color: var(--color-border);
  box-shadow: 0 8px 32px rgba(0, 0, 0, 0.04);
}

.header-inner {
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
}

.brand {
  display: flex;
  align-items: center;
  gap: 12px;
  flex-shrink: 0;
}

/* 主 Logo：正方形 app_logo，只约束高度避免拉伸 */
.brand .app-logo {
  height: 44px;
  width: auto;
}

/* 副 Logo：文字标 hero_title，只约束高度 */
.brand .wordmark-logo,
.hero-wordmark {
  height: auto;
  width: auto;
  max-height: 48px;
}

.site-nav {
  display: flex;
  align-items: center;
  gap: 36px;
  font-size: 15px;
  color: var(--color-ink-muted);
}

.site-nav a.is-active {
  color: var(--color-ink);
  font-weight: 500;
}

.header-actions {
  display: flex;
  align-items: center;
  gap: 16px;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 10px 22px;
  border-radius: 999px;
  font-size: 14px;
  font-weight: 500;
  border: 1px solid var(--color-ink);
  cursor: pointer;
  transition: background 0.2s, color 0.2s;
}

.btn-primary {
  background: var(--color-ink);
  color: #fff;
  border-color: var(--color-ink);
}

.btn-primary:hover {
  opacity: 1;
  background: #333;
}

.btn-ghost {
  background: transparent;
  color: var(--color-ink);
}

.nav-toggle {
  display: none;
  width: 40px;
  height: 40px;
  border: none;
  background: transparent;
  cursor: pointer;
}

.nav-toggle span {
  display: block;
  width: 22px;
  height: 2px;
  margin: 5px auto;
  background: var(--color-ink);
}

/* ---------- Hero ---------- */
.hero {
  position: relative;
  min-height: 100vh;
  padding-top: var(--header-h);
  overflow: hidden;
  display: flex;
  align-items: center;
}

.hero-bg {
  position: absolute;
  inset: 0;
  background: url("/static/images/page_bg.png") no-repeat center / cover;
  opacity: 0.55;
}

.hero-bg::after {
  content: "";
  position: absolute;
  inset: 0;
  background: linear-gradient(
    105deg,
    rgba(252, 253, 250, 0.92) 0%,
    rgba(252, 253, 250, 0.78) 42%,
    rgba(252, 253, 250, 0.4) 100%
  );
}

.hero-inner {
  position: relative;
  z-index: 1;
  display: grid;
  grid-template-columns: 1fr 1fr;
  align-items: center;
  gap: 48px;
  padding: 80px 0 100px;
}

.hero-copy h1 {
  font-family: var(--font-serif);
  font-size: clamp(36px, 4vw, 52px);
  font-weight: 700;
  line-height: 1.35;
  letter-spacing: 2px;
  margin-bottom: 20px;
}

.hero-wordmark {
  max-height: 56px;
  margin-bottom: 24px;
}

.hero-lead {
  font-size: 17px;
  color: var(--color-ink-muted);
  max-width: 480px;
  margin-bottom: 32px;
}

.hero-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin-bottom: 36px;
}

.hero-tag {
  padding: 6px 14px;
  border-radius: 999px;
  font-size: 13px;
  background: var(--color-card);
  border: 1px solid var(--color-border);
  color: var(--color-ink-muted);
}

.hero-visual {
  display: flex;
  justify-content: center;
  align-items: flex-end;
}

.hero-stele {
  width: min(380px, 90%);
  filter: drop-shadow(0 24px 48px rgba(0, 0, 0, 0.12));
}

/* ---------- Sections ---------- */
.section {
  padding: 100px 0;
  position: relative;
}

.section-alt {
  background: rgba(255, 255, 255, 0.45);
}

.section-head {
  text-align: center;
  max-width: 640px;
  margin: 0 auto 56px;
}

.section-label {
  font-size: 13px;
  letter-spacing: 6px;
  text-transform: uppercase;
  color: var(--color-ink-light);
  margin-bottom: 12px;
}

.section-title {
  font-family: var(--font-serif);
  font-size: clamp(28px, 3vw, 36px);
  font-weight: 600;
  letter-spacing: 2px;
  margin-bottom: 16px;
}

.section-desc {
  color: var(--color-ink-muted);
  font-size: 15px;
}

.feature-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 28px;
}

.feature-card {
  background: var(--color-card);
  border: 1px solid var(--color-border);
  border-radius: 16px;
  padding: 28px;
  backdrop-filter: blur(8px);
  transition: transform 0.25s, box-shadow 0.25s;
}

.feature-card:hover {
  transform: translateY(-4px);
  box-shadow: 0 16px 40px rgba(0, 0, 0, 0.06);
}

.feature-card img {
  width: 100%;
  border-radius: 10px;
  margin-bottom: 20px;
}

.feature-card h3 {
  font-family: var(--font-serif);
  font-size: 20px;
  margin-bottom: 10px;
}

.feature-card p {
  font-size: 14px;
  color: var(--color-ink-muted);
  line-height: 1.75;
}

.values-row {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 24px;
}

.value-item {
  text-align: center;
  padding: 36px 24px;
  border-radius: 16px;
  border: 1px solid var(--color-border);
  background: var(--color-paper);
}

.value-item h3 {
  font-family: var(--font-serif);
  font-size: 18px;
  margin-bottom: 12px;
}

.value-item p {
  font-size: 14px;
  color: var(--color-ink-muted);
}

.download-panel {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 40px;
  padding: 48px 56px;
  border-radius: 20px;
  background: linear-gradient(135deg, #1c1917 0%, #3d3a36 100%);
  color: #f5f5f4;
}

.download-panel h2 {
  font-family: var(--font-serif);
  font-size: 28px;
  margin-bottom: 12px;
}

.download-panel p {
  font-size: 14px;
  opacity: 0.85;
  max-width: 420px;
}

.download-badges {
  display: flex;
  flex-direction: column;
  gap: 12px;
  flex-shrink: 0;
}

.download-badge {
  padding: 14px 28px;
  border-radius: 12px;
  background: rgba(255, 255, 255, 0.12);
  border: 1px solid rgba(255, 255, 255, 0.2);
  font-size: 14px;
  text-align: center;
}

/* ---------- Doc pages ---------- */
.page-main {
  padding-top: calc(var(--header-h) + 48px);
  padding-bottom: 80px;
  min-height: 100vh;
  background: url("/static/images/page_bg.png") no-repeat center top / cover;
}

.page-main::before {
  content: "";
  position: fixed;
  inset: 0;
  background: rgba(252, 253, 250, 0.9);
  z-index: -1;
}

.doc-card {
  background: rgba(255, 255, 255, 0.9);
  border: 1px solid var(--color-border);
  border-radius: 16px;
  padding: 48px 56px;
  box-shadow: 0 12px 48px rgba(0, 0, 0, 0.04);
}

.doc-card h1 {
  font-family: var(--font-serif);
  font-size: 28px;
  margin-bottom: 8px;
}

.doc-meta {
  font-size: 13px;
  color: var(--color-ink-light);
  margin-bottom: 32px;
  padding-bottom: 24px;
  border-bottom: 1px solid var(--color-border);
}

.doc-card h2 {
  font-size: 17px;
  font-weight: 600;
  margin: 28px 0 12px;
}

.doc-card p,
.doc-card li {
  color: var(--color-ink-muted);
  margin-bottom: 12px;
}

.doc-card ul {
  padding-left: 22px;
}

/* ---------- Footer ---------- */
.site-footer {
  padding: 56px 0 40px;
  border-top: 1px solid var(--color-border);
  background: rgba(255, 255, 255, 0.6);
}

.footer-grid {
  display: grid;
  grid-template-columns: 1.2fr 1fr 1fr;
  gap: 40px;
  margin-bottom: 40px;
}

.footer-brand .app-logo {
  height: 48px;
  margin-bottom: 16px;
}

.footer-brand p {
  font-size: 14px;
  color: var(--color-ink-muted);
  max-width: 280px;
}

.footer-col h4 {
  font-size: 14px;
  font-weight: 600;
  margin-bottom: 16px;
}

.footer-col a,
.footer-col p {
  display: block;
  font-size: 14px;
  color: var(--color-ink-muted);
  margin-bottom: 10px;
}

.footer-bottom {
  padding-top: 24px;
  border-top: 1px solid var(--color-border);
  font-size: 13px;
  color: var(--color-ink-light);
  text-align: center;
}

/* ---------- Responsive ---------- */
@media (max-width: 960px) {
  .hero-inner {
    grid-template-columns: 1fr;
    text-align: center;
    padding: 48px 0 72px;
  }

  .hero-wordmark,
  .hero-lead {
    margin-left: auto;
    margin-right: auto;
  }

  .hero-tags {
    justify-content: center;
  }

  .feature-grid {
    grid-template-columns: 1fr;
  }

  .values-row {
    grid-template-columns: 1fr;
  }

  .download-panel {
    flex-direction: column;
    text-align: center;
    padding: 36px 28px;
  }

  .footer-grid {
    grid-template-columns: 1fr;
  }

  .doc-card {
    padding: 32px 24px;
  }
}

@media (max-width: 768px) {
  .site-nav,
  .header-actions .btn-ghost {
    display: none;
  }

  .site-nav.is-open {
    display: flex;
    flex-direction: column;
    position: absolute;
    top: var(--header-h);
    left: 0;
    right: 0;
    padding: 20px 24px 28px;
    background: rgba(252, 253, 250, 0.98);
    border-bottom: 1px solid var(--color-border);
    gap: 20px;
  }

  .nav-toggle {
    display: block;
  }

  .header-actions {
    gap: 8px;
  }

  .section {
    padding: 64px 0;
  }
}