/* 快练快考官网样式 — 简洁现代，移动优先，不依赖任何前端框架 */
:root {
  --primary: #3b5bdb;
  --primary-dark: #2b3fb0;
  --accent: #f59e0b;
  --text: #1f2937;
  --muted: #6b7280;
  --bg: #ffffff;
  --bg-soft: #f5f7ff;
  --border: #e5e7eb;
  --radius: 12px;
  --shadow: 0 1px 3px rgba(0, 0, 0, 0.06), 0 8px 24px rgba(59, 91, 219, 0.06);
}
* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Microsoft YaHei", Roboto, Helvetica, Arial, sans-serif;
  color: var(--text);
  background: var(--bg);
  line-height: 1.7;
  font-size: 16px;
}
h1, h2, h3, h4 { line-height: 1.3; margin: 0 0 0.5em; }
h1 { font-size: 1.9rem; }
h2 { font-size: 1.4rem; margin-top: 0; }
h3 { font-size: 1.1rem; }
h4 { font-size: 1rem; }
a { color: var(--primary); text-decoration: none; }
a:hover { text-decoration: underline; }
p { margin: 0 0 0.8em; }
.container { max-width: 1080px; margin: 0 auto; padding: 0 20px; }
.section { padding: 56px 20px; }
.center { text-align: center; }
.muted { color: var(--muted); }
.tag {
  display: inline-block; font-size: 0.75rem; font-weight: 600; color: var(--primary);
  background: var(--bg-soft); border: 1px solid #dce3ff; border-radius: 999px;
  padding: 2px 10px; margin-left: 8px; vertical-align: middle;
}

/* header / nav */
.site-header {
  position: sticky; top: 0; z-index: 50;
  background: rgba(255, 255, 255, 0.92); backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--border);
}
.nav-wrap { display: flex; align-items: center; justify-content: space-between; height: 60px; }
.brand { font-size: 1.15rem; font-weight: 800; color: var(--primary); }
.brand:hover { text-decoration: none; }
.brand-sub { font-size: 0.75rem; font-weight: 500; color: var(--muted); margin-left: 4px; }
.site-nav a {
  color: var(--text); font-weight: 500; margin-left: 22px; padding: 6px 0;
  border-bottom: 2px solid transparent;
}
.site-nav a:hover { text-decoration: none; color: var(--primary); }
.site-nav a.active { color: var(--primary); border-bottom-color: var(--primary); }
.nav-toggle { display: none; }

/* hero */
.hero {
  background: linear-gradient(135deg, #3b5bdb 0%, #5b7cff 60%, #7c9cff 100%);
  color: #fff; text-align: center; padding: 72px 20px;
}
.hero h1 { color: #fff; font-size: 2.1rem; max-width: 820px; margin: 0 auto 16px; }
.hero-sub { font-size: 1.05rem; max-width: 640px; margin: 0 auto 28px; opacity: 0.95; }
.hero-stats { display: flex; gap: 36px; justify-content: center; flex-wrap: wrap; margin-bottom: 24px; }
.stat { display: flex; flex-direction: column; }
.stat b { font-size: 1.8rem; }
.stat span { font-size: 0.85rem; opacity: 0.9; }
.hero-cta { font-size: 1.1rem; font-weight: 600; }

/* features */
.feature-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 20px; }
.feature-card {
  background: var(--bg); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 24px; box-shadow: var(--shadow); transition: transform 0.15s ease;
}
.feature-card:hover { transform: translateY(-3px); }
.feature-icon { font-size: 2rem; margin-bottom: 8px; }
.feature-card h3, .feature-card h2 { color: var(--primary); }

/* subjects */
.subject-grid { display: grid; grid-template-columns: repeat(4, 1fr); gap: 16px; }
.subject-card {
  display: block; color: var(--text); background: var(--bg-soft);
  border: 1px solid var(--border); border-radius: var(--radius);
  padding: 18px; transition: all 0.15s ease;
}
.subject-card:hover { text-decoration: none; border-color: var(--primary); transform: translateY(-2px); box-shadow: var(--shadow); }
.subject-card h3, .subject-card h4 { color: var(--primary-dark); margin-bottom: 6px; }
.subject-meta { font-size: 0.85rem; color: var(--muted); margin-bottom: 6px; }
.subject-desc { font-size: 0.88rem; color: var(--muted); margin: 0; }
.subject-desc-full { white-space: pre-line; }
.cat-block { margin-top: 32px; }
.cat-title { border-left: 4px solid var(--primary); padding-left: 10px; color: var(--primary-dark); }
.more-link { margin-top: 18px; font-weight: 600; }

/* how */
.how { background: var(--bg-soft); }
.how-list { max-width: 560px; margin: 0 auto; padding-left: 20px; }
.how-list li { margin-bottom: 10px; }

/* breadcrumb */
.breadcrumb { font-size: 0.88rem; color: var(--muted); margin-bottom: 18px; }

/* chapters */
.chapter-list { list-style: none; padding: 0; max-width: 760px; }
.chapter-list li { padding: 12px 14px; border: 1px solid var(--border); border-radius: 8px; margin-bottom: 8px; }
.chapter-desc { color: var(--muted); font-weight: 400; }

/* faq */
.faq-list { max-width: 760px; }
.faq-item { border: 1px solid var(--border); border-radius: 8px; margin-bottom: 10px; background: #fff; }
.faq-item summary { cursor: pointer; padding: 14px 16px; font-weight: 600; }
.faq-item summary::marker { color: var(--primary); }
.faq-item p { padding: 0 16px 14px; margin: 0; color: var(--muted); }

/* cta */
.cta-box {
  background: var(--bg-soft); border: 1px solid #dce3ff; border-radius: var(--radius);
  padding: 18px 22px; margin: 28px 0; font-weight: 600; color: var(--primary-dark);
}

/* footer */
.site-footer { background: #111827; color: #cbd5e1; margin-top: 40px; padding: 40px 0 20px; }
.footer-wrap { display: flex; justify-content: space-between; gap: 24px; flex-wrap: wrap; }
.footer-brand { font-size: 1.1rem; font-weight: 800; color: #fff; margin-bottom: 6px; }
.footer-desc { max-width: 420px; font-size: 0.88rem; color: #9ca3af; }
.footer-nav { display: flex; flex-direction: column; gap: 8px; }
.footer-nav a { color: #cbd5e1; font-size: 0.9rem; }
.footer-nav a:hover { color: #fff; }
.copy { border-top: 1px solid #1f2937; margin-top: 24px; padding-top: 16px; font-size: 0.8rem; color: #6b7280; }

/* responsive */
@media (max-width: 900px) {
  .feature-grid { grid-template-columns: repeat(2, 1fr); }
  .subject-grid { grid-template-columns: repeat(2, 1fr); }
}
@media (max-width: 600px) {
  h1 { font-size: 1.5rem; }
  .hero { padding: 48px 18px; }
  .hero h1 { font-size: 1.5rem; }
  .feature-grid, .subject-grid { grid-template-columns: 1fr; }
  .site-nav { display: none; }
}