:root {
  --brand: #2563eb;
  --brand-dark: #1d4ed8;
  --accent: #f59e0b;
  --bg: #f8fafc;
  --text: #1e293b;
  --muted: #64748b;
  --card: #ffffff;
  --border: #e2e8f0;
}

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

body {
  font-family: -apple-system, BlinkMacSystemFont, "PingFang SC", "Microsoft YaHei", "Segoe UI", sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.7;
}

.container { max-width: 860px; margin: 0 auto; padding: 0 20px; }

/* Header */
.site-header {
  background: #fff;
  border-bottom: 1px solid var(--border);
  position: sticky; top: 0; z-index: 10;
}
.nav { display: flex; align-items: center; justify-content: space-between; height: 60px; }
.brand { font-size: 18px; font-weight: 700; color: var(--text); text-decoration: none; }
.nav nav { display: flex; gap: 20px; }
.nav nav a { color: var(--muted); text-decoration: none; font-size: 15px; }
.nav nav a:hover, .nav nav a.active { color: var(--brand); font-weight: 600; }

/* Hero */
.hero {
  background: linear-gradient(135deg, #2563eb 0%, #4f46e5 100%);
  color: #fff; padding: 56px 0; text-align: center;
}
.hero h1 { font-size: 32px; margin-bottom: 12px; }
.hero p { font-size: 16px; opacity: .92; margin-bottom: 24px; }
.btn {
  display: inline-block; background: var(--accent); color: #1e293b;
  padding: 12px 28px; border-radius: 999px; text-decoration: none; font-weight: 700; font-size: 15px;
}
.btn:hover { background: #fbbf24; }

/* Sections */
main { padding: 40px 0 64px; }
.section-title { font-size: 22px; margin-bottom: 20px; }

/* Article cards */
.article-list { display: flex; flex-direction: column; gap: 16px; }
.card {
  background: var(--card); border: 1px solid var(--border); border-radius: 12px;
  padding: 20px 22px; text-decoration: none; color: var(--text); display: block;
  transition: box-shadow .15s, transform .15s;
}
.card:hover { box-shadow: 0 6px 20px rgba(30,41,59,.08); transform: translateY(-2px); }
.card-meta { display: flex; align-items: center; gap: 8px; margin-bottom: 8px; }
.date { font-size: 13px; color: var(--muted); }
.tag {
  font-size: 12px; background: #eff6ff; color: var(--brand);
  padding: 2px 10px; border-radius: 999px;
}
.card h3 { font-size: 18px; margin-bottom: 8px; }
.card p { font-size: 14px; color: var(--muted); margin-bottom: 10px; }
.more { font-size: 14px; color: var(--brand); font-weight: 600; }

/* Article detail */
.article-page { background: #fff; }
.article-body { max-width: 720px; margin: 0 auto; padding: 40px 20px 64px; }
.article-body h1 { font-size: 28px; line-height: 1.4; margin-bottom: 16px; }
.article-meta { color: var(--muted); font-size: 14px; margin-bottom: 28px; }
.article-body h2 { font-size: 20px; margin: 32px 0 12px; }
.article-body h3 { font-size: 17px; margin: 24px 0 8px; }
.article-body p { margin-bottom: 16px; }
.article-body ul, .article-body ol { margin: 0 0 16px 24px; }
.article-body li { margin-bottom: 8px; }
.article-body blockquote {
  border-left: 3px solid var(--brand); background: #f1f5f9;
  padding: 12px 16px; margin: 16px 0; border-radius: 0 8px 8px 0; color: #334155;
}
.back { display: inline-block; margin-bottom: 24px; color: var(--brand); text-decoration: none; font-size: 14px; }
.back:hover { text-decoration: underline; }

/* Vocab */
.vocab-toolbar { display: flex; flex-wrap: wrap; gap: 8px; margin-bottom: 20px; }
.vocab-toolbar .tag { cursor: pointer; border: none; font-size: 13px; padding: 6px 14px; }
.vocab-toolbar .tag.active { background: var(--brand); color: #fff; }
.word-card {
  background: #fff; border: 1px solid var(--border); border-radius: 12px; padding: 18px 22px; margin-bottom: 14px;
}
.word-head { display: flex; align-items: baseline; gap: 12px; flex-wrap: wrap; }
.word { font-size: 20px; font-weight: 700; color: var(--brand); }
.phonetic { color: var(--muted); font-size: 14px; }
.pos { font-size: 13px; background: #fef3c7; color: #92400e; padding: 2px 10px; border-radius: 999px; }
.meaning { margin-top: 8px; font-size: 15px; }
.example { margin-top: 8px; font-size: 14px; color: #334155; }
.example .cn { color: var(--muted); }
.reveal-btn {
  margin-top: 10px; border: 1px solid var(--brand); color: var(--brand); background: none;
  padding: 5px 16px; border-radius: 999px; cursor: pointer; font-size: 13px;
}
.reveal-btn:hover { background: #eff6ff; }
.empty { color: #64748b; font-size: 14px; }

/* Footer */
.site-footer { border-top: 1px solid var(--border); padding: 24px 0; text-align: center; color: var(--muted); font-size: 14px; }

@media (max-width: 600px) {
  .hero h1 { font-size: 26px; }
  .nav nav { gap: 14px; }
}