:root {
  --bg: #0d1220; --panel: #161d31; --panel2: #1d2640; --line: #2a3454;
  --text: #e8ecf6; --muted: #8b97b3; --accent: #e8b93e; --accent2: #5aa9e6;
  --good: #4cc38a; --bad: #ef6a6a;
}
* { box-sizing: border-box; margin: 0; padding: 0; }
body { background: var(--bg); color: var(--text); font-family: "Segoe UI", system-ui, sans-serif; line-height: 1.55; }
a { color: inherit; text-decoration: none; }

header.site {
  display: flex; align-items: center; gap: 14px; padding: 14px 22px;
  background: linear-gradient(180deg, #121a30, #0d1220); border-bottom: 1px solid var(--line);
  position: sticky; top: 0; z-index: 10;
}
header.site .logo { font-size: 1.15rem; font-weight: 700; }
header.site .logo span { color: var(--accent); }
header.site nav { margin-left: auto; display: flex; gap: 6px; }
header.site nav a { padding: 7px 14px; border-radius: 8px; color: var(--muted); font-weight: 600; }
header.site nav a:hover { color: var(--text); background: var(--panel2); }

#app { max-width: 1060px; margin: 0 auto; padding: 26px 20px 80px; }

.hero { text-align: center; padding: 34px 10px 10px; }
.hero h1 { font-size: 2.2rem; margin-bottom: 8px; }
.hero p { color: var(--muted); max-width: 720px; margin: 0 auto; }
.hero-stats { display: flex; gap: 14px; justify-content: center; margin: 22px 0 6px; flex-wrap: wrap; }
.stat { background: var(--panel); border: 1px solid var(--line); border-radius: 12px; padding: 12px 22px; min-width: 130px; }
.stat b { font-size: 1.4rem; color: var(--accent); display: block; }
.stat span { color: var(--muted); font-size: .85rem; }

.section-title { margin: 34px 0 14px; font-size: 1.25rem; border-left: 4px solid var(--accent); padding-left: 10px; }
.grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(235px, 1fr)); gap: 14px; }
.card {
  display: block; background: var(--panel); border: 1px solid var(--line); border-radius: 14px;
  padding: 16px; transition: transform .12s, border-color .12s;
}
.card:hover { transform: translateY(-3px); border-color: var(--accent); }
.card h3 { margin: 6px 0 2px; }
.card p { color: var(--muted); font-size: .88rem; }
.card-top { display: flex; justify-content: space-between; align-items: center; }
.card .icon { font-size: 1.6rem; }
.weight { background: var(--panel2); color: var(--accent); font-size: .75rem; font-weight: 700; padding: 3px 9px; border-radius: 999px; }
.done-badge { color: var(--good); }
.card-meta { color: var(--muted); font-size: .78rem; margin-top: 8px; }
.exam-card { border-color: var(--accent); }
.bar { height: 6px; background: var(--panel2); border-radius: 999px; margin-top: 10px; overflow: hidden; }
.bar .fill { height: 100%; background: var(--good); border-radius: 999px; }
.bar.big { height: 12px; }
.bar .fill.mid { background: var(--accent); }
.bar .fill.low { background: var(--bad); }
.footer-note { margin-top: 36px; color: var(--muted); text-align: center; font-size: .88rem; }

.back { display: inline-block; color: var(--muted); margin-bottom: 10px; font-weight: 600; }
.back:hover { color: var(--text); }
.page-title { font-size: 1.5rem; margin-bottom: 16px; }
.page-title .weight { vertical-align: middle; margin-left: 8px; }

.tabs { display: flex; gap: 8px; margin-bottom: 18px; }
.tab { background: var(--panel); color: var(--muted); border: 1px solid var(--line); border-radius: 10px; padding: 9px 18px; font-weight: 700; cursor: pointer; font-size: .95rem; }
.tab.active { color: var(--bg); background: var(--accent); border-color: var(--accent); }

.flashcard {
  background: var(--panel); border: 1px solid var(--line); border-radius: 16px; min-height: 240px;
  display: flex; align-items: center; justify-content: center; cursor: pointer; padding: 26px; margin-bottom: 16px;
}
.flashcard.known { border-color: rgba(76, 195, 138, .5); }
.fc-side { text-align: center; max-width: 720px; }
.fc-side.back .fc-text { color: var(--accent); }
.fc-label { color: var(--muted); font-size: .72rem; letter-spacing: 2px; margin-bottom: 12px; }
.fc-text { font-size: 1.12rem; }
.fc-hint { color: var(--muted); font-size: .75rem; margin-top: 16px; }
.fc-status { color: var(--muted); margin-bottom: 10px; }

.btn {
  background: var(--panel2); color: var(--text); border: 1px solid var(--line); border-radius: 10px;
  padding: 9px 16px; font-weight: 600; cursor: pointer; font-size: .93rem;
}
.btn:hover:not(:disabled) { border-color: var(--accent); }
.btn:disabled { opacity: .55; cursor: default; }
.btn.primary { background: var(--accent); color: #1a1408; border-color: var(--accent); }
.btn.subtle { color: var(--muted); font-size: .85rem; }
.btn.good-btn { border-color: rgba(76,195,138,.6); color: var(--good); }
.btn.bad-btn { border-color: rgba(239,106,106,.6); color: var(--bad); }
.btn.done { border-color: var(--good); color: var(--good); }
.btn-row { display: flex; gap: 10px; margin: 12px 0; flex-wrap: nowrap; }
.btn-row.center { justify-content: center; }
.btn-row.wrap { flex-wrap: wrap; }
.btn-col { display: flex; flex-direction: column; gap: 8px; margin: 12px 0; }
.btn.opt { text-align: left; }
.btn.opt.correct { border-color: var(--good); background: rgba(76,195,138,.12); }
.btn.opt.wrong { border-color: var(--bad); background: rgba(239,106,106,.12); }
.btn.opt.selected { border-color: var(--accent2); background: rgba(90,169,230,.12); }

.quiz-q { background: var(--panel); border: 1px solid var(--line); border-left: 4px solid var(--accent); border-radius: 12px; padding: 16px; font-size: 1.05rem; }
.result { text-align: center; background: var(--panel); border-radius: 16px; padding: 28px; margin-bottom: 20px; border: 1px solid var(--line); }
.result h2 { font-size: 2.6rem; }
.result.good h2 { color: var(--good); } .result.mid h2 { color: var(--accent); } .result.bad h2 { color: var(--bad); }
.miss { background: var(--panel); border: 1px solid var(--line); border-radius: 10px; padding: 12px 14px; margin: 8px 0; font-size: .9rem; }
.muted { color: var(--muted); }

.dom-bars { display: flex; flex-direction: column; gap: 8px; margin: 10px 0 20px; }
.dom-bar { display: grid; grid-template-columns: 240px 1fr 50px; gap: 10px; align-items: center; font-size: .85rem; }
.db-pct { color: var(--muted); text-align: right; }

.lab-root { max-width: 780px; }
.lab-intro { color: var(--muted); margin-bottom: 14px; }
.lab-scenario { background: var(--panel); border: 1px solid var(--line); border-left: 4px solid var(--accent2); border-radius: 12px; padding: 15px; margin: 12px 0; }
.lab-q { margin: 16px 0 4px; }
.lab-form { display: flex; gap: 12px; align-items: end; flex-wrap: wrap; margin: 12px 0; }
.lab-form label { display: flex; flex-direction: column; gap: 4px; color: var(--muted); font-size: .85rem; font-weight: 600; }
.lab-form input { background: var(--panel2); border: 1px solid var(--line); color: var(--text); border-radius: 8px; padding: 9px 12px; width: 170px; font-size: 1rem; }
.lab-feedback { border-radius: 10px; padding: 0; margin: 10px 0; font-size: .93rem; }
.lab-feedback.good { background: rgba(76,195,138,.1); border: 1px solid rgba(76,195,138,.45); padding: 12px 14px; }
.lab-feedback.bad { background: rgba(239,106,106,.1); border: 1px solid rgba(239,106,106,.45); padding: 12px 14px; }
.tag { background: var(--panel2); color: var(--accent2); font-size: .75rem; font-weight: 700; padding: 2px 9px; border-radius: 999px; }
.streak { color: var(--accent); font-weight: 700; margin-bottom: 6px; }

.chip { background: var(--panel2); border: 1px solid var(--line); color: var(--text); border-radius: 999px; padding: 8px 14px; margin: 4px; cursor: pointer; font-size: .88rem; }
.chip:hover:not(:disabled) { border-color: var(--accent); }
.chip:disabled { opacity: .4; }
.chip.picked { display: inline-block; opacity: 1; background: var(--panel); border-color: var(--accent2); }
.chip.matched { opacity: .45; border-color: var(--good); color: var(--good); }
.chip.sel { border-color: var(--accent); background: rgba(232,185,62,.15); }
.chip.shake { animation: shake .35s; border-color: var(--bad); }
@keyframes shake { 0%,100%{transform:translateX(0)} 25%{transform:translateX(-5px)} 75%{transform:translateX(5px)} }
.order-pool, .order-chosen { margin: 8px 0; min-height: 40px; }
.match-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 14px; margin: 12px 0; }
.match-col { display: flex; flex-direction: column; align-items: flex-start; }

.bio-canvas { width: 100%; max-width: 640px; background: var(--panel); border: 1px solid var(--line); border-radius: 12px; }
.bio-slider { width: 100%; max-width: 640px; margin: 12px 0 4px; accent-color: var(--accent); }
.bio-readout { color: var(--muted); margin-bottom: 8px; }

/* ---- textbook chapter reading view ---- */
.chapter { max-width: 760px; margin: 0 auto; font-size: 1.02rem; line-height: 1.7; }
.chapter h1 { font-size: 1.45rem; margin: 10px 0 18px; line-height: 1.3; }
.chapter h2 { font-size: 1.22rem; margin: 34px 0 12px; padding-left: 10px; border-left: 4px solid var(--accent); }
.chapter h3 { font-size: 1.05rem; margin: 24px 0 10px; color: var(--accent2); }
.chapter h4 { font-size: 1rem; margin: 18px 0 8px; }
.chapter p { margin: 0 0 14px; }
.chapter ul, .chapter ol { margin: 0 0 14px 24px; }
.chapter li { margin-bottom: 6px; }
.chapter blockquote {
  background: var(--panel); border: 1px solid var(--line); border-left: 4px solid var(--accent2);
  border-radius: 10px; padding: 12px 16px; margin: 0 0 16px;
}
.chapter blockquote p { margin-bottom: 8px; }
.chapter blockquote p:last-child { margin-bottom: 0; }
.chapter code { background: var(--panel2); border: 1px solid var(--line); border-radius: 5px; padding: 1px 6px; font-size: .9em; }
.chapter hr { border: none; border-top: 1px solid var(--line); margin: 26px 0; }
.chapter a { color: var(--accent2); text-decoration: underline; }
.chapter .table-wrap { overflow-x: auto; margin: 0 0 16px; }
.chapter table { border-collapse: collapse; width: 100%; font-size: .92rem; }
.chapter th, .chapter td { border: 1px solid var(--line); padding: 8px 10px; text-align: left; vertical-align: top; }
.chapter th { background: var(--panel2); color: var(--accent); }
.chapter tr:nth-child(even) td { background: rgba(255,255,255,.02); }

@media (max-width: 640px) {
  .dom-bar { grid-template-columns: 120px 1fr 44px; }
  .match-grid { grid-template-columns: 1fr; }
  header.site { padding: 12px; }
}