/* 全局变量与重置 / 通用区块 / Footer / 回到顶部 */
/* 由 extract.py 从原路书切出，勿手工重排 */

/* ========== 全局变量与重置 ========== */
:root {
  --c-primary: #E8743B;
  --c-primary-dark: #C95A28;
  --c-secondary: #2A9D8F;
  --c-secondary-dark: #1F7A6E;
  --c-accent: #E9C46A;
  --c-dark: #264653;
  --c-dark-soft: #3A5A6B;
  --c-text: #2D3436;
  --c-text-light: #636E72;
  --c-bg: #FAF6F0;
  --c-bg-card: #FFFFFF;
  --c-bg-warm: #FDF3E7;
  --c-border: #E8DFD3;
  --c-shadow: rgba(38, 70, 83, 0.08);
  --c-shadow-lg: rgba(38, 70, 83, 0.15);
  --font-serif: 'Noto Serif SC', 'Songti SC', 'SimSun', serif;
  --font-sans: 'Noto Sans SC', 'PingFang SC', 'Microsoft YaHei', sans-serif;
  --radius: 12px;
  --radius-lg: 20px;
  --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

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

html { scroll-behavior: smooth; }

body {
  font-family: var(--font-sans);
  color: var(--c-text);
  background: var(--c-bg);
  line-height: 1.7;
  overflow-x: hidden;
}

a { color: var(--c-secondary); text-decoration: none; }
a:hover { color: var(--c-secondary-dark); }

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

/* ========== 通用区块 ========== */
.section {
  padding: 80px 24px;
  max-width: 1200px;
  margin: 0 auto;
}
.section-header {
  text-align: center;
  margin-bottom: 48px;
}
.section-tag {
  display: inline-block;
  font-size: 14px;
  font-weight: 600;
  color: var(--c-primary);
  letter-spacing: 2px;
  text-transform: uppercase;
  margin-bottom: 12px;
}
.section-title {
  font-family: var(--font-serif);
  font-size: clamp(26px, 3.5vw, 38px);
  font-weight: 700;
  color: var(--c-dark);
  margin-bottom: 14px;
}
.section-desc {
  font-size: 15.5px;
  color: var(--c-text-light);
  max-width: 700px;
  margin: 0 auto;
}

/* ========== Footer ========== */
.footer {
  background: var(--c-dark);
  color: rgba(255,255,255,0.6);
  text-align: center;
  padding: 40px 24px;
  font-size: 14px;
}
.footer strong { color: var(--c-accent); font-family: var(--font-serif); }

/* ========== 回到顶部 ========== */
.back-top {
  position: fixed;
  bottom: 32px; right: 32px;
  width: 48px; height: 48px;
  border-radius: 50%;
  background: var(--c-primary);
  color: #fff;
  border: none;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  box-shadow: 0 4px 16px rgba(232, 116, 59, 0.4);
  opacity: 0;
  visibility: hidden;
  transition: var(--transition);
  z-index: 99;
}
.back-top.show { opacity: 1; visibility: visible; }
.back-top:hover { transform: translateY(-3px); }
.back-top svg { width: 20px; height: 20px; }