:root {
  --bg: #f4f7fb;
  --card: #ffffff;
  --ink: #233044;
  --ink-soft: #5b6b80;
  --line: #e6ecf3;
  --primary: #3b82f6;
  --primary-dark: #2563eb;
  --primary-soft: #e8f0fe;
  --accent: #f59e0b;
  --success: #16a34a;
  --success-soft: #e7f6ec;
  --danger: #ef4444;
  --danger-soft: #fdeaea;
  --radius: 16px;
  --shadow: 0 4px 18px rgba(35,48,68,.08);
}
* { box-sizing: border-box; -webkit-tap-highlight-color: transparent; }
html, body { margin: 0; padding: 0; }
body {
  font-family: "PingFang SC","Microsoft YaHei","Hiragino Sans GB",system-ui,-apple-system,Segoe UI,Roboto,sans-serif;
  background: var(--bg);
  color: var(--ink);
  font-size: 16px;
  line-height: 1.6;
}
button { font-family: inherit; cursor: pointer; }

/* ---------- App bar ---------- */
.app-bar {
  position: sticky; top: 0; z-index: 20;
  display: flex; align-items: center; gap: 12px; flex-wrap: wrap;
  padding: 10px 16px;
  background: var(--card);
  border-bottom: 1px solid var(--line);
  box-shadow: 0 2px 10px rgba(35,48,68,.05);
}
.brand { display: flex; align-items: center; gap: 10px; }
.brand .logo { font-size: 28px; }
.brand-text strong { display: block; font-size: 17px; }
.brand-text small { color: var(--ink-soft); font-size: 12px; }
.nav { display: flex; gap: 6px; flex-wrap: wrap; flex: 1; }
.nav-btn {
  border: none; background: transparent; color: var(--ink-soft);
  padding:8px 12px; border-radius: 10px; font-size: 15px; font-weight: 600;
  transition: .15s;
}
.nav-btn:hover { background: var(--primary-soft); color: var(--primary-dark); }
.nav-btn.active { background: var(--primary); color: #fff; }
.user-box { display: flex; align-items: center; gap: 8px; }
.user-pill {
  background: var(--primary-soft); color: var(--primary-dark);
  padding: 6px 12px; border-radius: 999px; font-size: 14px; font-weight: 600;
}

.app-main { max-width: 1000px; margin: 0 auto; padding: 18px 14px 60px; }

/* ---------- Generic ---------- */
.card {
  background: var(--card); border: 1px solid var(--line);
  border-radius: var(--radius); box-shadow: var(--shadow);
  padding: 18px; margin-bottom: 16px;
}
.card h2 { margin: 0 0 12px; font-size: 19px; }
.card h3 { margin: 14px 0 8px; font-size: 16px; color: var(--ink-soft); }
.row { display: flex; gap: 10px; flex-wrap: wrap; align-items: center; }
.spread { justify-content: space-between; }
.muted { color: var(--ink-soft); font-size: 14px; }
.section-title { font-size: 20px; font-weight: 700; margin: 4px 0 14px; }

.btn {
  border: none; border-radius: 12px; padding: 11px 16px; font-size: 15px; font-weight: 700;
  background: var(--primary); color: #fff; transition: .15s; min-height: 44px;
}
.btn:hover { background: var(--primary-dark); }
.btn:disabled { opacity: .5; cursor: not-allowed; }
.btn.ghost { background: var(--primary-soft); color: var(--primary-dark); }
.btn.ghost:hover { background: #d8e6fd; }
.btn.green { background: var(--success); }
.btn.green:hover { filter: brightness(.95); }
.btn.warn { background: var(--accent); }
.btn.danger { background: var(--danger); }
.btn.sm { padding: 7px 12px; font-size: 14px; min-height: 36px; border-radius: 10px; }
.chip {
  display: inline-flex; align-items: center; gap: 6px;
  background: var(--primary-soft); color: var(--primary-dark);
  padding: 6px 12px; border-radius: 999px; font-size: 14px; border: none; font-weight: 600;
}
.chip.active { background: var(--primary); color: #fff; }
.select, .input, textarea {
  border: 1px solid var(--line); border-radius: 10px; padding: 10px 12px;
  font-size: 15px; background: #fff; color: var(--ink); min-height: 44px; width: 100%;
}
.input:focus, .select:focus { outline: 2px solid var(--primary-soft); border-color: var(--primary); }

/* ---------- Unit grid ---------- */
.unit-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(140px,1fr)); gap: 12px; }
.unit-card {
  background: linear-gradient(135deg,#eaf2ff,#f6f9ff);
  border: 1px solid var(--line); border-radius: 14px; padding: 14px; text-align: left;
  transition: .15s;
}
.unit-card:hover { transform: translateY(-2px); box-shadow: var(--shadow); }
.unit-card .un { font-size: 13px; color: var(--primary-dark); font-weight: 700; }
.unit-card .th { font-size: 17px; font-weight: 800; margin-top: 4px; }
.unit-card .kq { font-size: 12px; color: var(--ink-soft); margin-top: 6px; }

/* ---------- Reader ---------- */
.subnav { display: flex; gap: 8px; flex-wrap: wrap; margin-bottom: 12px; }
.reading-text { font-size: 19px; line-height: 2.1; }
.sentence {
  display: inline; cursor: pointer; padding: 2px 4px; border-radius: 8px;
  transition: background .15s; border-bottom: 2px dashed transparent;
}
.sentence:hover { background: var(--primary-soft); }
.sentence.playing { background: var(--accent); color: #fff; }
.sentence.done { border-bottom-color: var(--success); }
.word-token { cursor: pointer; border-bottom: 2px dotted var(--primary); padding: 0 2px; }
.word-token:hover { background: var(--primary-soft); }
.player-bar {
  position: sticky; bottom: 0; z-index: 15; background: var(--card);
  border-top: 1px solid var(--line); padding: 12px 14px; display: flex; gap: 10px;
  flex-wrap: wrap; align-items: center; box-shadow: 0 -4px 16px rgba(35,48,68,.08);
}
.status { font-size: 14px; padding: 6px 10px; border-radius: 8px; background: var(--bg); color: var(--ink-soft); }
.status.loading { color: var(--primary-dark); background: var(--primary-soft); }
.status.playing { color: var(--success); background: var(--success-soft); }
.audio-list { display: flex; gap: 8px; flex-wrap: wrap; margin-top: 6px; }

.vocab-list { display: grid; grid-template-columns: repeat(auto-fill, minmax(160px,1fr)); gap: 10px; }
.vocab-item {
  border: 1px solid var(--line); border-radius: 12px; padding: 12px; display: flex;
  flex-direction: column; gap: 4px; cursor: pointer; transition: .15s;
}
.vocab-item:hover { border-color: var(--primary); background: var(--primary-soft); }
.vocab-item .w { font-weight: 800; font-size: 17px; }
.vocab-item .pos { font-size: 12px; color: var(--ink-soft); }
.vocab-item .m { color: var(--ink-soft); font-size: 14px; }

/* ---------- Quiz ---------- */
.q-card { margin-bottom: 14px; }
.q-prompt { font-size: 18px; font-weight: 700; margin-bottom: 12px; display: flex; align-items: center; gap: 8px; flex-wrap: wrap; }
.q-index { background: var(--primary); color:#fff; border-radius: 8px; padding: 2px 9px; font-size: 14px; }
.q-audio-btn { border:none; background: var(--primary-soft); color: var(--primary-dark); border-radius: 10px; padding: 6px 10px; font-size: 14px; }
.options { display: grid; gap: 10px; }
.opt {
  border: 2px solid var(--line); border-radius: 12px; padding: 12px 14px; font-size: 16px;
  background: #fff; text-align: left; transition: .12s; display: flex; gap: 10px; align-items: center;
}
.opt:hover { border-color: var(--primary); }
.opt.correct { border-color: var(--success); background: var(--success-soft); }
.opt.wrong { border-color: var(--danger); background: var(--danger-soft); }
.opt .mk { width: 26px; height: 26px; border-radius: 50%; border: 2px solid var(--line); display:flex; align-items:center; justify-content:center; font-weight:800; flex:none; }
.opt.correct .mk { background: var(--success); color:#fff; border-color: var(--success); }
.opt.wrong .mk { background: var(--danger); color:#fff; border-color: var(--danger); }
.feedback { margin-top: 10px; font-size: 15px; padding: 10px 12px; border-radius: 10px; }
.feedback.ok { background: var(--success-soft); color: #117a37; }
.feedback.no { background: var(--danger-soft); color: #b3261e; }
.write-box { display: flex; gap: 10px; flex-wrap: wrap; align-items: center; }
.write-box .input { flex: 1; min-width: 200px; font-size: 18px; letter-spacing: 1px; }

/* ---------- Wrong book / exam ---------- */
.wb-item { border:1px solid var(--line); border-radius:12px; padding:12px 14px; margin-bottom:10px; }
.wb-item .meta { font-size:13px; color: var(--ink-soft); }
.wb-item .q { font-weight:700; margin:4px 0; font-size:16px; }
.wb-item .a { font-size:14px; }
.tag { font-size:12px; padding:2px 8px; border-radius:999px; background: var(--bg); color: var(--ink-soft); }
.tag.en { background: var(--primary-soft); color: var(--primary-dark); }
.switch { display:inline-flex; align-items:center; gap:8px; font-size:15px; }

.timer { font-size: 22px; font-weight: 800; color: var(--accent); font-variant-numeric: tabular-nums; }
.result-big { font-size: 40px; font-weight: 900; color: var(--primary); }

/* ---------- Account ---------- */
.auth-card { max-width: 380px; margin: 30px auto; }
.center { text-align: center; }
.empty { text-align:center; color: var(--ink-soft); padding: 40px 10px; }
.kpi { display:flex; gap:12px; flex-wrap:wrap; }
.kpi .k { flex:1; min-width: 110px; background: var(--primary-soft); border-radius:12px; padding:14px; }
.kpi .k b { display:block; font-size:24px; color: var(--primary-dark); }
.kpi .k span { font-size:13px; color: var(--ink-soft); }

/* ---------- Toast ---------- */
.toast {
  position: fixed; left: 50%; bottom: 80px; transform: translateX(-50%) translateY(20px);
  background: rgba(35,48,68,.94); color: #fff; padding: 10px 18px; border-radius: 10px;
  font-size: 14px; opacity: 0; pointer-events: none; transition: .25s; z-index: 50; max-width: 90vw;
}
.toast.show { opacity: 1; transform: translateX(-50%) translateY(0); }

.progress-line { height: 8px; background: var(--line); border-radius: 999px; overflow:hidden; }
.progress-line > i { display:block; height:100%; background: var(--success); }

/* ---------- Mobile ---------- */
@media (max-width: 640px) {
  .app-bar { padding: 8px 10px; }
  .brand-text small { display: none; }
  .nav-btn { padding: 7px 10px; font-size: 14px; }
  .app-main { padding: 14px 10px 80px; }
  .reading-text { font-size: 18px; line-height: 2; }
  .unit-grid { grid-template-columns: repeat(auto-fill, minmax(46%,1fr)); }
  .vocab-list { grid-template-columns: repeat(auto-fill, minmax(46%,1fr)); }
  .player-bar { padding: 10px; }
  .btn { padding: 10px 13px; }
}