/* 数学闯关 静态站点 共享样式 */
:root {
  --primary: #6366f1;
  --primary-deep: #4f46e5;
  --secondary: #06b6d4;
  --accent: #f59e0b;
  --success: #10b981;
  --warning: #f97316;
  --bg: #fafaff;
  --surface: #ffffff;
  --border: #e5e7eb;
  --text: #1f2937;
  --text-secondary: #4b5563;
  --text-tertiary: #9ca3af;
  --radius-sm: 8px;
  --radius-md: 14px;
  --radius-lg: 22px;
  --shadow-sm: 0 1px 3px rgba(99, 102, 241, 0.08);
  --shadow-md: 0 8px 24px rgba(99, 102, 241, 0.10);
}

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

html, body {
  font-family: -apple-system, BlinkMacSystemFont, 'PingFang SC', 'Helvetica Neue',
               Helvetica, Arial, 'Microsoft YaHei', sans-serif;
  font-size: 16px;
  line-height: 1.7;
  color: var(--text);
  background: var(--bg);
  -webkit-font-smoothing: antialiased;
}

a {
  color: var(--primary);
  text-decoration: none;
  transition: color .15s ease;
}
a:hover { color: var(--primary-deep); text-decoration: underline; }

/* 顶部导航 */
.nav {
  position: sticky;
  top: 0;
  z-index: 10;
  background: rgba(255, 255, 255, 0.85);
  backdrop-filter: saturate(180%) blur(14px);
  -webkit-backdrop-filter: saturate(180%) blur(14px);
  border-bottom: 1px solid var(--border);
}
.nav-inner {
  max-width: 960px;
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 14px 24px;
}
.brand {
  display: flex;
  align-items: center;
  gap: 10px;
  font-weight: 700;
  font-size: 17px;
  color: var(--text);
}
.brand-mark {
  width: 32px; height: 32px;
  border-radius: 9px;
  background: linear-gradient(135deg, var(--primary), var(--secondary));
  display: inline-flex;
  align-items: center;
  justify-content: center;
  color: white;
  font-size: 18px;
  box-shadow: var(--shadow-sm);
}
.nav-links {
  display: flex;
  gap: 24px;
  font-size: 14px;
}
.nav-links a {
  color: var(--text-secondary);
  font-weight: 500;
}
.nav-links a:hover { color: var(--primary); text-decoration: none; }
.nav-links a.active { color: var(--primary); font-weight: 600; }

/* 主体容器 */
.container {
  max-width: 760px;
  margin: 0 auto;
  padding: 48px 24px 80px;
}
.container-wide {
  max-width: 960px;
  margin: 0 auto;
  padding: 64px 24px 80px;
}

/* Hero */
.hero {
  text-align: center;
  padding: 32px 16px 48px;
}
.hero-emoji {
  font-size: 72px;
  display: inline-block;
  filter: drop-shadow(0 4px 14px rgba(99, 102, 241, 0.25));
}
.hero h1 {
  font-size: 38px;
  font-weight: 800;
  margin-top: 12px;
  background: linear-gradient(135deg, var(--primary), var(--secondary));
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
}
.hero .subtitle {
  font-size: 17px;
  color: var(--text-secondary);
  margin-top: 12px;
}

/* 卡片 / 区块 */
.card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 28px 28px;
  box-shadow: var(--shadow-sm);
  margin-bottom: 20px;
}

.feature-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 16px;
  margin-top: 32px;
}
.feature {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  padding: 22px;
  transition: transform .2s ease, box-shadow .2s ease;
}
.feature:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
}
.feature .icon {
  font-size: 30px;
  margin-bottom: 10px;
}
.feature h3 {
  font-size: 16px;
  font-weight: 700;
  margin-bottom: 4px;
  color: var(--text);
}
.feature p {
  font-size: 14px;
  color: var(--text-secondary);
}

/* 隐私 / 条款 文档样式 */
.doc h1 {
  font-size: 32px;
  font-weight: 800;
  margin-bottom: 8px;
}
.doc .meta {
  color: var(--text-tertiary);
  font-size: 14px;
  margin-bottom: 32px;
}
.doc h2 {
  font-size: 22px;
  font-weight: 700;
  margin-top: 36px;
  margin-bottom: 12px;
  color: var(--text);
  border-left: 4px solid var(--primary);
  padding-left: 12px;
}
.doc h3 {
  font-size: 17px;
  font-weight: 600;
  margin-top: 22px;
  margin-bottom: 8px;
  color: var(--text);
}
.doc p, .doc li {
  color: var(--text-secondary);
  font-size: 15.5px;
}
.doc ul, .doc ol {
  margin: 8px 0 12px 22px;
}
.doc li {
  margin-bottom: 6px;
}
.doc strong { color: var(--text); }

.callout {
  background: linear-gradient(135deg, rgba(99, 102, 241, 0.08), rgba(6, 182, 212, 0.06));
  border: 1px solid rgba(99, 102, 241, 0.18);
  border-radius: var(--radius-md);
  padding: 16px 18px;
  margin: 16px 0;
  font-size: 14.5px;
  color: var(--text-secondary);
}
.callout.warn {
  background: linear-gradient(135deg, rgba(245, 158, 11, 0.10), rgba(249, 115, 22, 0.06));
  border-color: rgba(245, 158, 11, 0.25);
}

table.simple {
  width: 100%;
  border-collapse: collapse;
  margin: 12px 0;
  font-size: 14.5px;
}
table.simple th, table.simple td {
  border: 1px solid var(--border);
  padding: 10px 12px;
  text-align: left;
  vertical-align: top;
}
table.simple th {
  background: #f5f5fb;
  color: var(--text);
  font-weight: 600;
}

/* 底部 */
.footer {
  border-top: 1px solid var(--border);
  margin-top: 64px;
  padding: 28px 24px;
  text-align: center;
  color: var(--text-tertiary);
  font-size: 13px;
}
.footer a { color: var(--text-tertiary); margin: 0 6px; }
.footer a:hover { color: var(--primary); }

/* 移动端 */
@media (max-width: 640px) {
  .hero h1 { font-size: 30px; }
  .hero-emoji { font-size: 60px; }
  .container { padding: 32px 18px 60px; }
  .container-wide { padding: 40px 18px 60px; }
  .card { padding: 22px 20px; }
  .nav-links { gap: 14px; font-size: 13px; }
  .nav-inner { padding: 12px 16px; }
  .doc h1 { font-size: 26px; }
  .doc h2 { font-size: 19px; }
}