/* ══════════════════════════════════════════════════
   自学平台 — 中式传统风格设计系统
   ══════════════════════════════════════════════════ */

/* ── 字体 ── */
@font-face {
  font-family: 'Crimson Pro';
  src: url('fonts/CrimsonPro-Regular.ttf') format('truetype');
  font-weight: 400;
}
@font-face {
  font-family: 'Crimson Pro';
  src: url('fonts/CrimsonPro-Bold.ttf') format('truetype');
  font-weight: 700;
}
@font-face {
  font-family: 'Lora';
  src: url('fonts/Lora-Regular.ttf') format('truetype');
  font-weight: 400;
}
@font-face {
  font-family: 'Lora';
  src: url('fonts/Lora-Bold.ttf') format('truetype');
  font-weight: 700;
}
@font-face {
  font-family: 'Lora';
  src: url('fonts/Lora-Italic.ttf') format('truetype');
  font-weight: 400;
  font-style: italic;
}

/* ── CSS 变量 ── */
:root {
  --bg: #f6edda;
  --bg2: #faf3e2;
  --ink: #2b1d15;
  --ink-soft: rgba(43,29,21,0.72);
  --muted: rgba(43,29,21,0.52);
  --rule: #d7b98c;
  --accent: #9f2d20;
  --accent2: #b98a36;
  --accent2-soft: rgba(185,138,54,0.15);
  --accent-soft: rgba(159,45,32,0.08);
  --panel-border: #c9a87c;
  --shadow: rgba(43,29,21,0.06);
  --card-front-bg: #fdf8ed;
  --filter-bg: rgba(246,237,218,0.6);
  --veil: rgba(250,243,226,0.85);
  --ok: #3f7a47;
  --font-heading: 'Crimson Pro', 'STKaiti', 'KaiTi', '楷体', serif;
  --font-body: 'Lora', 'STSong', 'SimSun', '宋体', serif;
  --font-ui: 'Lora', 'PingFang SC', 'Microsoft YaHei', '微软雅黑', sans-serif;
}

/* ── 全局重置 ── */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

html {
  font-size: 17px;
  scroll-behavior: smooth;
}

body {
  font-family: var(--font-body);
  color: var(--ink);
  background:
    radial-gradient(ellipse at 20% 10%, rgba(185,138,54,0.06) 0%, transparent 60%),
    radial-gradient(ellipse at 80% 90%, rgba(159,45,32,0.04) 0%, transparent 60%),
    linear-gradient(180deg, var(--bg) 0%, var(--bg2) 50%, var(--bg) 100%);
  line-height: 1.75;
  min-height: 100vh;
  position: relative;
}

/* 宣纸纹理 */
body::before {
  content: '';
  position: fixed;
  inset: 0;
  background:
    repeating-linear-gradient(0deg, transparent, transparent 2px, rgba(43,29,21,0.012) 2px, rgba(43,29,21,0.012) 4px);
  pointer-events: none;
  z-index: 0;
  mask-image: radial-gradient(ellipse at center, black 40%, transparent 70%);
}

a { color: var(--accent); text-decoration: none; transition: color 180ms ease; }
a:hover { color: var(--accent2); }

/* ── 顶部导航栏 ── */
header.nav {
  position: sticky;
  top: 0;
  z-index: 100;
  background: linear-gradient(180deg, rgba(250,243,226,0.97), rgba(250,243,226,0.92));
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--rule);
  box-shadow: 0 1px 8px var(--shadow);
}

.nav-inner {
  max-width: 960px;
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0.6rem 1.2rem;
}

.logo {
  font-family: var(--font-heading);
  font-size: 1.15rem;
  font-weight: 700;
  color: var(--accent);
  letter-spacing: 0.04em;
  text-decoration: none;
}

.logo-mark {
  display: inline-block;
  padding: 0.2rem 0.8rem;
  border: 1px solid var(--accent);
  border-radius: 0.3rem;
  background: rgba(159,45,32,0.04);
}

.nav-links {
  display: flex;
  gap: 0.2rem;
}

.nav-links a {
  padding: 0.4rem 0.8rem;
  border-radius: 0.4rem;
  font-family: var(--font-ui);
  font-size: 0.88rem;
  font-weight: 600;
  color: var(--ink-soft);
  transition: all 180ms ease;
}

.nav-links a:hover {
  color: var(--accent);
  background: var(--accent-soft);
}

/* 学科导航下拉菜单 */
.nav-links .sub-nav-dropdown {
  position: relative;
  display: inline-block;
}
.nav-links .sub-nav-dropdown-menu {
  display: none;
  position: absolute;
  top: 100%;
  left: 0;
  margin-top: 0;
  min-width: 140px;
  background: var(--bg2, #fff8ea);
  border: 1px solid var(--rule, #d7b98c);
  border-radius: 0.5rem;
  box-shadow: 0 4px 16px rgba(0,0,0,0.12);
  padding: 0.4rem 0;
  z-index: 300;
}
.nav-links .sub-nav-dropdown:hover .sub-nav-dropdown-menu {
  display: block;
}
.nav-links .sub-nav-dropdown-menu a {
  display: block;
  padding: 0.5rem 1rem;
  font-size: 0.85rem;
  font-weight: 500;
  color: var(--ink-soft, #755f4a);
  white-space: nowrap;
}
.nav-links .sub-nav-dropdown-menu a:hover {
  color: var(--accent, #9f2d20);
  background: var(--accent-soft, rgba(159,45,32,0.06));
}
.nav-links .has-dropdown::after {
  content: ' ▾';
  font-size: 0.7em;
  vertical-align: middle;
}
/* ── 页面容器 ── */
.page {
  max-width: 960px;
  margin: 0 auto;
  padding: 1.5rem 1.5rem 4rem;
  position: relative;
  z-index: 1;
}

/* ── 卷轴式卡片 ── */
.card {
  background: linear-gradient(135deg, var(--card-front-bg), rgba(255,248,234,0.5));
  border: 1px solid var(--panel-border);
  border-radius: 0.8rem;
  padding: 1.5rem;
  margin: 1.2rem 0;
  box-shadow: 0 2px 12px var(--shadow);
}

.card-title {
  font-family: var(--font-heading);
  font-size: 1.1rem;
  font-weight: 700;
  color: var(--accent);
  margin-bottom: 0.6rem;
}

/* ── 面板 ── */
.panel {
  background: linear-gradient(180deg, #faf3e2, var(--card-front-bg), #faf3e2);
  border: 1px solid var(--panel-border);
  border-radius: 1rem;
  padding: 1.8rem;
  margin: 1.5rem 0;
  box-shadow:
    0 4px 20px var(--shadow),
    inset 0 0 0 1px rgba(255,255,255,0.5);
  position: relative;
}

.panel::before {
  content: '';
  position: absolute;
  top: 0.5rem;
  left: 0.5rem;
  right: 0.5rem;
  bottom: 0.5rem;
  border: 1px solid rgba(201,168,124,0.35);
  border-radius: 0.7rem;
  pointer-events: none;
}

/* ── 表格 ── */
.table-wrap {
  overflow-x: auto;
  margin: 1.2rem 0;
  border: 1px solid var(--rule);
  border-radius: 0.5rem;
}

table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.9rem;
}

thead th {
  background: linear-gradient(180deg, rgba(159,45,32,0.08), rgba(159,45,32,0.03));
  color: var(--accent);
  font-weight: 700;
  padding: 0.7rem 0.8rem;
  text-align: left;
  border-bottom: 2px solid var(--rule);
  font-family: var(--font-heading);
}

tbody td {
  padding: 0.6rem 0.8rem;
  border-bottom: 1px solid rgba(215,185,140,0.4);
  vertical-align: top;
}

tbody tr:last-child td { border-bottom: none; }
tbody tr:hover { background: rgba(185,138,54,0.05); }

/* ── 标题 ── */
h1 {
  font-family: var(--font-heading);
  font-size: 2rem;
  font-weight: 700;
  color: var(--accent);
  letter-spacing: 0.05em;
}

h2 {
  font-family: var(--font-heading);
  font-size: 1.6rem;
  font-weight: 700;
  color: var(--accent);
  margin: 2rem 0 1rem;
  padding-bottom: 0.5rem;
  border-bottom: 1px solid var(--rule);
}

h3 {
  font-family: var(--font-heading);
  font-size: 1.2rem;
  font-weight: 700;
  color: var(--ink);
  margin: 1.5rem 0 0.8rem;
}

h4 {
  font-family: var(--font-heading);
  font-size: 1.05rem;
  font-weight: 700;
  color: var(--accent2);
  margin: 1.2rem 0 0.6rem;
}

/* ── 段落 ── */
p { margin-bottom: 0.8rem; }
strong { color: var(--ink); font-weight: 700; }

/* ── 列表 ── */
ul, ol { margin: 0.6rem 0 0.8rem 1.2rem; }
li { margin-bottom: 0.4rem; }

/* ── 标签 ── */
.tag {
  display: inline-block;
  padding: 0.15rem 0.6rem;
  border-radius: 999px;
  font-size: 0.75rem;
  font-weight: 700;
  letter-spacing: 0.03em;
}

.tag-red { background: rgba(159,45,32,0.1); color: var(--accent); }
.tag-gold { background: var(--accent2-soft); color: var(--accent2); }

/* ── 按钮 ── */
.btn {
  display: inline-block;
  padding: 0.5rem 1.4rem;
  border: 1px solid var(--accent);
  border-radius: 999px;
  font-family: var(--font-ui);
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--accent);
  background: transparent;
  cursor: pointer;
  transition: all 180ms ease;
}

.btn:hover {
  color: #fff;
  background: var(--accent);
}

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

.btn-primary:hover {
  background: #8b261b;
  border-color: #8b261b;
}

/* ── 响应式 ── */
@media (max-width: 720px) {
  html { font-size: 15px; }
  .page { padding: 1rem 0.8rem 3rem; }
  .nav-inner { flex-wrap: wrap; gap: 0.4rem; padding: 0.5rem 0.8rem; }
  .nav-links { gap: 0; }
  .nav-links a { padding: 0.3rem 0.5rem; font-size: 0.78rem; }
}