/* ===================================================
   HSK4 Mandarin Zone — Shared Styles
   common.css
   =================================================== */

/* === DESIGN TOKENS === */
:root {
  --ink: #1a1a2e;
  --paper: #faf8f5;
  --accent: #c23b22;
  --accent-soft: #e8d5d0;
  --jade: #2d6a4f;
  --jade-soft: #d8f3dc;
  --gold: #b8860b;
  --gold-soft: #fef3cd;
  --mist: #e8e4df;
  --stone: #6b6b6b;
  --correct: #2d6a4f;
  --wrong: #c23b22;
  --radius: 12px;
  --shadow: 0 2px 20px rgba(26,26,46,0.08);
  --shadow-lg: 0 8px 40px rgba(26,26,46,0.12);
}

/* === RESET & BASE === */
* { margin: 0; padding: 0; box-sizing: border-box; }

body {
  font-family: 'DM Sans', sans-serif;
  background: var(--paper);
  color: var(--ink);
  line-height: 1.6;
  min-height: 100vh;
}

.chinese { font-family: 'Noto Sans SC', 'Noto Serif SC', sans-serif; }
.serif-cn { font-family: 'Noto Serif SC', serif; }
.sr-only {
  position: absolute; width: 1px; height: 1px;
  padding: 0; margin: -1px; overflow: hidden;
  clip: rect(0,0,0,0); border: 0;
}

/* === HEADER === */
header {
  background: var(--ink);
  color: var(--paper);
  padding: 0;
  position: sticky;
  top: 0;
  z-index: 100;
}

.header-inner {
  max-width: 900px;
  margin: 0 auto;
  padding: 16px 24px;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.logo {
  display: flex;
  align-items: center;
  gap: 12px;
  text-decoration: none;
  color: var(--paper);
}

.logo-mark {
  width: 36px; height: 36px;
  background: var(--accent);
  border-radius: 8px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-family: 'Noto Serif SC', serif;
  font-size: 20px;
  font-weight: 700;
  color: white;
}

.logo-text {
  font-weight: 700;
  font-size: 16px;
  letter-spacing: -0.3px;
}
.logo-text span { color: var(--accent); }

.site-nav {
  display: flex;
  align-items: center;
  gap: 16px;
}

.nav-link {
  color: var(--paper);
  opacity: 0.7;
  text-decoration: none;
  font-size: 14px;
  font-weight: 500;
  transition: opacity 0.2s;
}
.nav-link:hover { opacity: 1; }

.gh-link {
  color: var(--paper);
  opacity: 0.7;
  text-decoration: none;
  font-size: 14px;
  display: flex;
  align-items: center;
  gap: 6px;
  transition: opacity 0.2s;
}
.gh-link:hover { opacity: 1; }
.gh-link svg { width: 18px; height: 18px; fill: currentColor; }

/* === MAIN LAYOUT === */
main {
  max-width: 900px;
  margin: 0 auto;
  padding: 24px;
}

/* === HERO === */
.hero {
  text-align: center;
  padding: 48px 0 40px;
}

.hero-badge {
  display: inline-block;
  background: var(--accent-soft);
  color: var(--accent);
  font-size: 13px;
  font-weight: 600;
  padding: 6px 16px;
  border-radius: 100px;
  margin-bottom: 20px;
  letter-spacing: 0.5px;
  text-transform: uppercase;
}

.hero h1 {
  font-family: 'Noto Serif SC', serif;
  font-size: clamp(26px, 5vw, 40px);
  font-weight: 700;
  line-height: 1.2;
  margin-bottom: 12px;
}

.hero h1 .accent { color: var(--accent); }

.hero p {
  font-size: 17px;
  color: var(--stone);
  max-width: 560px;
  margin: 0 auto;
}

/* === SECTION TITLE === */
.section-title {
  font-size: 14px;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 1px;
  color: var(--stone);
  margin: 40px 0 16px;
  padding-bottom: 8px;
  border-bottom: 2px solid var(--mist);
}

/* === STATS ROW === */
.stats-row {
  display: flex;
  justify-content: center;
  gap: 32px;
  margin-top: 28px;
  flex-wrap: wrap;
}

.stat { text-align: center; }

.stat-num {
  font-size: 28px;
  font-weight: 700;
  color: var(--ink);
}

.stat-label {
  font-size: 13px;
  color: var(--stone);
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

/* === BUTTONS === */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 10px 20px;
  border-radius: 10px;
  font-size: 14px;
  font-weight: 600;
  border: none;
  cursor: pointer;
  text-decoration: none;
  transition: all 0.2s;
  font-family: 'DM Sans', sans-serif;
}

.btn-primary { background: var(--accent); color: white; }
.btn-primary:hover { background: #a83220; }
.btn-secondary { background: var(--mist); color: var(--ink); }
.btn-secondary:hover { background: #d8d4cf; }
.btn-ghost {
  background: transparent;
  color: var(--stone);
  border: 1px solid var(--mist);
}
.btn-ghost:hover { background: var(--mist); }
.btn-jade { background: var(--jade); color: white; }
.btn-jade:hover { background: #245a42; }

/* === CTA BANNER === */
.cta-banner {
  background: var(--ink);
  color: var(--paper);
  border-radius: var(--radius);
  padding: 40px;
  text-align: center;
  margin: 48px 0;
}

.cta-banner h3 {
  font-family: 'Noto Serif SC', serif;
  font-size: 22px;
  margin-bottom: 8px;
}

.cta-banner p {
  opacity: 0.7;
  font-size: 15px;
  margin-bottom: 20px;
  color: var(--paper);
}

/* === FOOTER === */
footer {
  text-align: center;
  padding: 24px;
  color: var(--stone);
  font-size: 13px;
  border-top: 1px solid var(--mist);
  margin-top: 20px;
}

footer a { color: var(--accent); text-decoration: none; }
footer a:hover { text-decoration: underline; }

/* === LOADING === */
.loading {
  text-align: center;
  padding: 60px;
  color: var(--stone);
}

.spinner {
  width: 32px; height: 32px;
  border: 3px solid var(--mist);
  border-top: 3px solid var(--accent);
  border-radius: 50%;
  animation: spin 0.8s linear infinite;
  margin: 0 auto 16px;
}

@keyframes spin { to { transform: rotate(360deg); } }

/* === RESPONSIVE === */
@media (max-width: 600px) {
  .hero { padding: 32px 0 28px; }
  .stats-row { gap: 20px; }
  .cta-banner { padding: 28px 20px; }
}