:root {
  --bg: #f5f6fa;
  --surface: #ffffff;
  --surface-2: #eef1f7;
  --text: #171a22;
  --muted: #646b7a;
  --brand: #24498f;
  --brand-2: #18356d;
  --accent: #dce7ff;
  --success: #157347;
  --warning: #9a6700;
  --danger: #b42318;
  --border: #dfe3ec;
  --shadow: 0 12px 30px rgba(25, 34, 55, .08);
  --radius: 18px;
  --max: 1180px;
}
* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  color: var(--text);
  background: var(--bg);
  font-family: Inter, ui-sans-serif, -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
  line-height: 1.65;
}
a { color: inherit; text-decoration: none; }
button, input, select { font: inherit; }
button { cursor: pointer; }
.container { width: min(calc(100% - 32px), var(--max)); margin: 0 auto; }
.site-header {
  position: sticky; top: 0; z-index: 20;
  background: rgba(255,255,255,.92); backdrop-filter: blur(18px);
  border-bottom: 1px solid rgba(223,227,236,.9);
}
.nav { min-height: 68px; display: flex; align-items: center; gap: 24px; }
.brand { display: inline-flex; align-items: center; gap: 10px; font-weight: 850; letter-spacing: -.02em; }
.brand-mark { width: 36px; height: 36px; border-radius: 11px; display: grid; place-items: center; color: white; background: linear-gradient(145deg, var(--brand), #4772c9); font-weight: 900; }
.nav-links { display: flex; align-items: center; gap: 6px; margin-left: auto; }
.nav-links a { padding: 9px 13px; border-radius: 10px; color: var(--muted); font-weight: 650; }
.nav-links a:hover, .nav-links a[aria-current="page"] { background: var(--surface-2); color: var(--text); }
.mobile-nav-toggle { display: none; margin-left: auto; border: 0; background: var(--surface-2); border-radius: 10px; padding: 8px 11px; }
.hero { padding: 76px 0 46px; }
.hero-grid { display: grid; grid-template-columns: 1.25fr .75fr; gap: 34px; align-items: center; }
.eyebrow { display: inline-flex; padding: 6px 11px; border-radius: 999px; background: var(--accent); color: var(--brand-2); font-weight: 750; font-size: .88rem; }
h1 { margin: 18px 0 14px; font-size: clamp(2.4rem, 6vw, 5rem); line-height: 1.04; letter-spacing: -.055em; }
h2 { margin: 0 0 16px; font-size: clamp(1.55rem, 3vw, 2.35rem); line-height: 1.18; letter-spacing: -.035em; }
h3 { margin: 0 0 8px; line-height: 1.25; }
.hero p { max-width: 650px; color: var(--muted); font-size: 1.08rem; }
.actions { display: flex; flex-wrap: wrap; gap: 12px; margin-top: 28px; }
.btn { display: inline-flex; align-items: center; justify-content: center; gap: 8px; border: 1px solid transparent; border-radius: 12px; padding: 11px 17px; font-weight: 750; min-height: 46px; }
.btn-primary { color: white; background: var(--brand); }
.btn-primary:hover { background: var(--brand-2); }
.btn-secondary { background: var(--surface); border-color: var(--border); }
.btn-secondary:hover { border-color: #b9c2d4; }
.btn-danger { color: var(--danger); background: #fff4f2; border-color: #ffd3cc; }
.hero-card { background: linear-gradient(145deg, #1d376b, #315eae); color: white; padding: 26px; border-radius: 26px; box-shadow: 0 28px 55px rgba(29,55,107,.24); }
.hero-word { font-family: Georgia, serif; font-size: 2.4rem; font-weight: 750; }
.hero-card .muted-light { color: rgba(255,255,255,.75); }
.hero-example { border-top: 1px solid rgba(255,255,255,.2); margin-top: 18px; padding-top: 18px; }
.section { padding: 44px 0; }
.section-head { display: flex; justify-content: space-between; gap: 24px; align-items: end; margin-bottom: 20px; }
.muted { color: var(--muted); }
.grid-4 { display: grid; grid-template-columns: repeat(4, 1fr); gap: 16px; }
.grid-3 { display: grid; grid-template-columns: repeat(3, 1fr); gap: 18px; }
.card { background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius); padding: 20px; box-shadow: 0 3px 12px rgba(25,34,55,.035); }
.card:hover.lift { transform: translateY(-2px); box-shadow: var(--shadow); transition: .18s ease; }
.stat-number { font-size: 2rem; font-weight: 850; letter-spacing: -.04em; }
.level-badge, .pos-badge, .label-badge { display: inline-flex; align-items: center; border-radius: 999px; padding: 4px 9px; font-size: .78rem; font-weight: 750; }
.level-badge { color: var(--brand-2); background: var(--accent); }
.pos-badge { color: #5f3d00; background: #fff1c7; }
.label-badge { color: #3e4b60; background: var(--surface-2); }
.search-panel { padding: 24px; background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius); }
.search-row { display: grid; grid-template-columns: 1fr 160px 190px; gap: 12px; }
.input, .select { width: 100%; border: 1px solid var(--border); background: white; border-radius: 12px; padding: 12px 14px; outline: none; min-height: 48px; }
.input:focus, .select:focus { border-color: #6c8dcb; box-shadow: 0 0 0 4px rgba(65,103,175,.12); }
.results-meta { display: flex; justify-content: space-between; align-items: center; margin: 18px 2px 12px; color: var(--muted); }
.word-list { display: grid; grid-template-columns: repeat(2, 1fr); gap: 12px; }
.word-row { display: grid; grid-template-columns: 1fr auto; gap: 16px; align-items: center; background: var(--surface); border: 1px solid var(--border); border-radius: 15px; padding: 16px 18px; }
.word-row:hover { border-color: #aeb9cf; box-shadow: 0 8px 20px rgba(25,34,55,.06); }
.word-title { display: flex; flex-wrap: wrap; gap: 8px; align-items: baseline; }
.word-title strong { font-family: Georgia, serif; font-size: 1.35rem; }
.word-zh { color: var(--muted); margin-top: 4px; }
.pagination { display: flex; justify-content: center; gap: 10px; margin-top: 24px; }
.empty { padding: 42px 18px; text-align: center; background: var(--surface); border: 1px dashed #bac3d4; border-radius: var(--radius); color: var(--muted); }
.page-hero { padding: 42px 0 24px; }
.page-hero h1 { font-size: clamp(2rem, 5vw, 3.8rem); margin: 10px 0; }
.word-layout { display: grid; grid-template-columns: minmax(0, 1fr) 310px; gap: 22px; align-items: start; padding-bottom: 56px; }
.word-main, .word-aside { display: grid; gap: 16px; }
.definition { font-size: 1.28rem; font-weight: 720; }
.stress { letter-spacing: .08em; color: var(--brand); font-weight: 800; }
.example { padding: 16px 0; border-bottom: 1px solid var(--border); }
.example:last-child { border-bottom: 0; }
.example-it { font-family: Georgia, serif; font-size: 1.15rem; font-weight: 650; }
.forms-grid { display: grid; grid-template-columns: repeat(2, minmax(0,1fr)); gap: 12px; }
.form-item { background: var(--surface-2); border-radius: 12px; padding: 11px 13px; }
.form-item small { display: block; color: var(--muted); margin-bottom: 3px; }
.study-shell { max-width: 760px; margin: 0 auto; padding: 34px 0 64px; }
.progress-track { height: 9px; border-radius: 999px; background: #e2e7f0; overflow: hidden; }
.progress-fill { height: 100%; background: var(--brand); width: 0; transition: width .25s ease; }
.study-card { min-height: 410px; display: grid; align-content: center; text-align: center; padding: clamp(26px, 6vw, 58px); }
.study-word { font-family: Georgia, serif; font-size: clamp(2.4rem, 8vw, 5rem); line-height: 1; }
.study-answer { margin-top: 24px; display: none; }
.study-answer.visible { display: block; }
.study-actions { display: grid; grid-template-columns: repeat(2, 1fr); gap: 12px; margin-top: 18px; }
.quiz-options { display: grid; gap: 10px; margin-top: 22px; }
.quiz-option { text-align: left; padding: 14px 16px; border: 1px solid var(--border); border-radius: 12px; background: white; }
.quiz-option:hover { border-color: #8ca1c9; }
.quiz-option.correct { border-color: #4ba278; background: #ecfff5; }
.quiz-option.wrong { border-color: #dc776e; background: #fff1ef; }
.dashboard-grid { display: grid; grid-template-columns: 1.2fr .8fr; gap: 18px; }
.due-list { display: grid; gap: 10px; }
.due-row { display: flex; justify-content: space-between; gap: 16px; padding: 11px 0; border-bottom: 1px solid var(--border); }
.due-row:last-child { border-bottom: 0; }
.footer { padding: 36px 0 48px; border-top: 1px solid var(--border); color: var(--muted); background: var(--surface); }
.footer-grid { display: grid; grid-template-columns: 1fr auto; gap: 20px; align-items: start; }
.footer-links { display: flex; flex-wrap: wrap; gap: 15px; }
.notice { border-left: 4px solid var(--warning); background: #fff9e8; padding: 14px 16px; border-radius: 10px; color: #5d4500; }
.toast { position: fixed; right: 20px; bottom: 20px; z-index: 100; background: #1d2430; color: white; padding: 12px 16px; border-radius: 12px; opacity: 0; transform: translateY(10px); pointer-events: none; transition: .2s; }
.toast.visible { opacity: 1; transform: translateY(0); }
.skeleton { border-radius: 10px; min-height: 60px; background: linear-gradient(90deg,#edf0f5 25%,#f8f9fb 38%,#edf0f5 63%); background-size: 400% 100%; animation: shimmer 1.4s infinite; }
@keyframes shimmer { 0% { background-position: 100% 0; } 100% { background-position: 0 0; } }
@media (max-width: 900px) {
  .hero-grid, .dashboard-grid, .word-layout { grid-template-columns: 1fr; }
  .grid-4 { grid-template-columns: repeat(2,1fr); }
  .grid-3 { grid-template-columns: 1fr; }
  .word-aside { grid-template-columns: repeat(2,1fr); }
}
@media (max-width: 680px) {
  .container { width: min(calc(100% - 22px), var(--max)); }
  .mobile-nav-toggle { display: inline-flex; }
  .nav-links { position: absolute; top: 62px; left: 11px; right: 11px; display: none; flex-direction: column; align-items: stretch; padding: 10px; border: 1px solid var(--border); background: white; border-radius: 14px; box-shadow: var(--shadow); }
  .nav-links.open { display: flex; }
  .search-row { grid-template-columns: 1fr; }
  .word-list, .grid-4, .forms-grid, .word-aside { grid-template-columns: 1fr; }
  .hero { padding-top: 42px; }
  .hero-card { padding: 22px; }
  .study-actions { grid-template-columns: 1fr; }
  .footer-grid { grid-template-columns: 1fr; }
}
@media (prefers-reduced-motion: reduce) { * { scroll-behavior: auto !important; transition: none !important; animation: none !important; } }

.pricing-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 18px; }
.price { font-size: 2.2rem; font-weight: 900; letter-spacing: -.04em; }
.price small { font-size: .9rem; color: var(--muted); font-weight: 650; }
.feature-list { margin: 18px 0; padding-left: 20px; color: var(--muted); }
.feature-list li { margin: 7px 0; }
.plan-highlight { border-color: #87a6df; box-shadow: 0 14px 34px rgba(36,73,143,.12); }
.validation-box { background: #f0f5ff; border: 1px solid #cad9f8; padding: 18px; border-radius: 14px; }
@media (max-width: 900px) { .pricing-grid { grid-template-columns: 1fr; } }