:root {
  --bg: #f5f7fb;
  --card: #ffffff;
  --soft: #eef3ff;
  --text: #14213d;
  --muted: #64748b;
  --line: #dbe3f0;
  --primary: #1f4fbf;
  --primary-strong: #173f9a;
  --danger: #b42318;
  --good: #16794b;
  --warn: #a15c00;
  --shadow: 0 10px 28px rgba(22, 34, 58, 0.08);
  --radius: 18px;
}

html[data-theme="dark"] {
  --bg: #0d1320;
  --card: #151e2e;
  --soft: #1b2942;
  --text: #edf3ff;
  --muted: #9fb0c9;
  --line: #2a3850;
  --primary: #7aa2ff;
  --primary-strong: #9ab7ff;
  --danger: #ff8d86;
  --good: #5bd19a;
  --warn: #ffc36b;
  --shadow: 0 12px 32px rgba(0, 0, 0, 0.24);
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  line-height: 1.5;
}
button, select, input { font: inherit; }
button { -webkit-tap-highlight-color: transparent; }
.hidden { display: none !important; }
.muted { color: var(--muted); }
.wrap { flex-wrap: wrap; }
.full { width: 100%; }

.app-shell { min-height: 100vh; }
.topbar {
  position: sticky;
  top: 0;
  z-index: 30;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  padding: 14px max(16px, env(safe-area-inset-left));
  border-bottom: 1px solid var(--line);
  background: color-mix(in srgb, var(--card) 92%, transparent);
  backdrop-filter: blur(12px);
}
.topbar h1 { margin: 2px 0 0; font-size: 1.25rem; }
.eyebrow { color: var(--primary); font-size: .72rem; font-weight: 800; letter-spacing: .08em; text-transform: uppercase; }
.main { width: min(1180px, 100%); margin: 0 auto; padding: 20px 16px 96px; }
.page { display: none; }
.page.active { display: block; }

.card {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 20px;
  margin-bottom: 16px;
}
.hero { display: grid; grid-template-columns: minmax(0, 1fr) auto; align-items: center; gap: 20px; }
.hero h2 { margin: 10px 0 6px; font-size: clamp(1.45rem, 4vw, 2.35rem); line-height: 1.15; }
.hero p { max-width: 760px; margin: 0; }
.hero-actions { display: flex; gap: 10px; flex-wrap: wrap; }
.section-head { display: flex; align-items: flex-start; gap: 14px; margin-bottom: 16px; }
.section-head h2, .section-head h3 { margin: 0; }
.section-head p { margin: 4px 0 0; }
.between { justify-content: space-between; }

.btn, .icon-btn, .nav-btn, .quick-card {
  border: 0;
  cursor: pointer;
  transition: transform .12s ease, opacity .12s ease, background .12s ease, border-color .12s ease;
}
.btn:active, .icon-btn:active, .quick-card:active { transform: translateY(1px); }
.btn {
  min-height: 46px;
  padding: 11px 15px;
  border-radius: 12px;
  font-weight: 750;
}
.btn.primary { background: var(--primary); color: white; }
.btn.primary:hover { background: var(--primary-strong); }
.btn.secondary { background: var(--soft); color: var(--text); border: 1px solid var(--line); }
.btn.ghost { background: transparent; color: var(--text); border: 1px solid var(--line); }
.btn.danger { background: var(--danger); color: #fff; }
.btn.compact { min-height: 38px; padding: 8px 11px; font-size: .88rem; }
.btn:disabled { opacity: .48; cursor: not-allowed; }
.icon-btn { width: 42px; height: 42px; border-radius: 50%; background: var(--soft); color: var(--text); }
.icon-btn.small { width: 34px; height: 34px; }

.pill, .badge, .score-badge {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  border-radius: 999px;
  font-weight: 750;
}
.pill { padding: 5px 9px; font-size: .78rem; color: var(--primary); background: var(--soft); }
.badge { padding: 6px 10px; font-size: .78rem; color: var(--muted); background: var(--soft); border: 1px solid var(--line); }
.score-badge { padding: 10px 16px; font-size: 1.1rem; color: #fff; background: var(--primary); }

.stat-grid { display: grid; grid-template-columns: repeat(4, minmax(0, 1fr)); gap: 12px; margin-bottom: 16px; }
.stat { padding: 16px; background: var(--card); border: 1px solid var(--line); border-radius: 16px; box-shadow: var(--shadow); }
.stat span { display: block; color: var(--muted); font-size: .8rem; }
.stat strong { display: block; margin-top: 4px; font-size: 1.55rem; }
.quick-grid { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 12px; }
.quick-card { text-align: left; min-height: 96px; padding: 16px; border-radius: 15px; color: var(--text); background: var(--soft); border: 1px solid var(--line); }
.quick-card strong, .quick-card span { display: block; }
.quick-card span { color: var(--muted); margin-top: 4px; font-size: .85rem; }

.integrity-list { display: grid; gap: 8px; }
.integrity-row { display: flex; justify-content: space-between; gap: 14px; align-items: flex-start; padding: 10px 12px; border: 1px solid var(--line); border-radius: 12px; }
.integrity-row.good { border-color: color-mix(in srgb, var(--good) 35%, var(--line)); }
.integrity-row.bad { border-color: color-mix(in srgb, var(--danger) 45%, var(--line)); }
.integrity-row small { color: var(--muted); }

.dataset-grid { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 12px; }
.dataset-card { border: 1px solid var(--line); border-radius: 16px; padding: 16px; background: color-mix(in srgb, var(--card) 96%, var(--soft)); }
.dataset-card h3 { margin: 0 0 6px; }
.dataset-meta { display: flex; flex-wrap: wrap; gap: 6px; margin: 10px 0 14px; }
.dataset-actions { display: grid; grid-template-columns: 1fr 1fr; gap: 8px; }
.week-row { display: flex; flex-wrap: wrap; gap: 6px; margin-top: 10px; }
.week-btn { border: 1px solid var(--line); color: var(--text); background: transparent; border-radius: 9px; padding: 7px 9px; cursor: pointer; font-weight: 700; }

.form-grid { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 14px; }
.form-grid label { display: grid; gap: 6px; font-size: .84rem; font-weight: 700; color: var(--muted); }
select, input[type="text"] { width: 100%; min-height: 46px; padding: 10px 12px; color: var(--text); background: var(--card); border: 1px solid var(--line); border-radius: 12px; }
.toggle-row { display: flex; flex-wrap: wrap; gap: 10px; margin: 16px 0; }
.check-chip { display: inline-flex; align-items: center; gap: 8px; border: 1px solid var(--line); border-radius: 999px; padding: 9px 12px; font-size: .87rem; cursor: pointer; }
.pool-box { display: grid; grid-template-columns: 1fr 1fr; gap: 10px; margin: 16px 0; }
.pool-box > div { display: flex; justify-content: space-between; gap: 10px; padding: 12px; background: var(--soft); border-radius: 12px; }

.test-shell { min-height: 70vh; }
.sticky-card { position: sticky; top: 78px; z-index: 10; }
.exam-title-row { display: flex; justify-content: space-between; gap: 16px; align-items: flex-start; }
.exam-title-row h2 { margin: 2px 0; font-size: 1.05rem; }
.timer-box { min-width: 110px; text-align: center; padding: 8px 12px; background: var(--soft); border-radius: 12px; }
.timer-box span { display: block; color: var(--muted); font-size: .72rem; }
.timer-box strong { font-size: 1.1rem; font-variant-numeric: tabular-nums; }
.timer-box.warning strong { color: var(--danger); }
.progress-track { height: 7px; background: var(--soft); border-radius: 999px; overflow: hidden; margin: 14px 0 10px; }
.progress-fill { height: 100%; width: 0; background: var(--primary); transition: width .2s ease; }
.status-strip { display: flex; flex-wrap: wrap; gap: 16px; color: var(--muted); font-size: .82rem; }
.status-strip b { color: var(--text); }
.exam-layout { display: grid; grid-template-columns: minmax(0, 1fr) 300px; gap: 16px; align-items: start; }
.question-card { min-height: 500px; }
.question-top { display: flex; align-items: flex-start; justify-content: space-between; gap: 14px; }
.source-label { display: block; margin-top: 7px; color: var(--muted); font-size: .78rem; }
.question-text { font-size: 1.08rem; font-weight: 700; margin: 22px 0 16px; white-space: pre-wrap; }
.code-block { overflow-x: auto; padding: 14px; border-radius: 12px; background: #0e1726; color: #e7edf7; font-size: .86rem; }
.options { display: grid; gap: 10px; margin: 16px 0 20px; }
.option {
  width: 100%;
  display: grid;
  grid-template-columns: 34px minmax(0, 1fr);
  align-items: start;
  gap: 10px;
  text-align: left;
  padding: 13px;
  border: 1px solid var(--line);
  border-radius: 13px;
  background: var(--card);
  color: var(--text);
  cursor: pointer;
}
.option:hover { border-color: var(--primary); }
.option.selected { border-color: var(--primary); background: var(--soft); }
.option.correct { border-color: var(--good); }
.option.wrong { border-color: var(--danger); }
.option-key { width: 30px; height: 30px; display: grid; place-items: center; border-radius: 50%; background: var(--soft); font-weight: 800; text-transform: uppercase; }
.solution-box { margin-top: 14px; padding: 14px; border: 1px solid var(--line); border-radius: 12px; background: var(--soft); }
.solution-box .answer { font-weight: 800; color: var(--good); }
.question-actions { display: grid; grid-template-columns: auto auto 1fr auto; gap: 8px; margin-top: 24px; }
.palette-card { position: sticky; top: 238px; }
.palette-legend { display: grid; grid-template-columns: 1fr 1fr; gap: 6px 10px; margin-bottom: 12px; color: var(--muted); font-size: .72rem; }
.palette-legend span { display: flex; align-items: center; gap: 6px; }
.dot { width: 10px; height: 10px; border-radius: 50%; background: var(--line); }
.dot.current { background: var(--primary); }
.dot.answered { background: var(--good); }
.dot.review { background: #8b5cf6; }
.dot.unseen { background: var(--line); }
.palette { display: grid; grid-template-columns: repeat(5, 1fr); gap: 7px; margin-bottom: 14px; max-height: 360px; overflow: auto; }
.palette-btn { aspect-ratio: 1; border-radius: 10px; border: 1px solid var(--line); background: var(--card); color: var(--text); cursor: pointer; font-weight: 800; font-size: .82rem; }
.palette-btn.answered { background: color-mix(in srgb, var(--good) 16%, var(--card)); border-color: color-mix(in srgb, var(--good) 55%, var(--line)); }
.palette-btn.review { background: color-mix(in srgb, #8b5cf6 18%, var(--card)); border-color: #8b5cf6; }
.palette-btn.current { outline: 3px solid color-mix(in srgb, var(--primary) 35%, transparent); border-color: var(--primary); }
.palette-card .btn + .btn { margin-top: 8px; }

.empty-state { text-align: center; padding: 54px 20px; }
.result-stats { margin-top: 16px; margin-bottom: 0; }
.review-list, .history-list { display: grid; gap: 12px; }
.review-item, .history-item { border: 1px solid var(--line); border-radius: 14px; padding: 14px; }
.review-item.good { border-left: 5px solid var(--good); }
.review-item.bad { border-left: 5px solid var(--danger); }
.review-item.unanswered { border-left: 5px solid var(--warn); }
.review-item h4, .history-item h4 { margin: 0 0 8px; }
.review-lines { display: grid; gap: 4px; margin-top: 10px; font-size: .9rem; }
.review-solution { margin-top: 10px; padding: 10px; background: var(--soft); border-radius: 10px; white-space: pre-wrap; }
.history-item { display: flex; justify-content: space-between; gap: 14px; align-items: center; }
.history-item .score { font-weight: 900; font-size: 1.05rem; white-space: nowrap; }

.bottom-nav {
  position: fixed;
  left: 50%;
  transform: translateX(-50%);
  bottom: 0;
  z-index: 40;
  width: min(760px, 100%);
  display: grid;
  grid-template-columns: repeat(5, 1fr);
  padding: 8px 8px max(8px, env(safe-area-inset-bottom));
  background: color-mix(in srgb, var(--card) 94%, transparent);
  border: 1px solid var(--line);
  border-bottom: 0;
  border-radius: 18px 18px 0 0;
  backdrop-filter: blur(12px);
  box-shadow: 0 -10px 24px rgba(22, 34, 58, .08);
}
.nav-btn { min-height: 48px; color: var(--muted); background: transparent; border-radius: 10px; font-weight: 800; font-size: .8rem; }
.nav-btn.active { color: var(--primary); background: var(--soft); }

@media (max-width: 900px) {
  .dataset-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .exam-layout { grid-template-columns: 1fr; }
  .palette-card { position: static; }
  .sticky-card { top: 70px; }
}

@media (max-width: 680px) {
  .main { padding: 12px 10px 92px; }
  .card { padding: 15px; border-radius: 15px; }
  .hero { grid-template-columns: 1fr; }
  .hero-actions .btn { flex: 1; }
  .stat-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .quick-grid, .dataset-grid, .form-grid { grid-template-columns: 1fr; }
  .pool-box { grid-template-columns: 1fr; }
  .exam-title-row { align-items: center; }
  .question-top { display: grid; }
  .question-actions { grid-template-columns: 1fr 1fr; }
  .question-actions .primary { grid-column: 1 / -1; }
  .palette { grid-template-columns: repeat(6, 1fr); }
  .history-item { align-items: flex-start; }
}