:root {
  --bg: #eef1f6;
  --bg-2: #e4e9f2;
  --card: #ffffff;
  --ink: #152033;
  --muted: #5b6b82;
  --line: #d5deea;
  --accent: #ad5c1e;
  --accent-ink: #7a3f12;
  --accent-soft: #fbe9d9;
  --ok: #1f8a5b;
  --ok-bg: #e7f7ee;
  --bad: #c0392b;
  --bad-bg: #fdecea;
  --flag: #b45309;
  --flag-bg: #fff4e5;
  --shadow: 0 10px 30px rgba(21, 32, 51, 0.08);
  --radius: 16px;
  --mono: ui-monospace, "Cascadia Code", "SF Mono", Menlo, Consolas, monospace;
  --sans: "Segoe UI", system-ui, -apple-system, sans-serif;
}

* { box-sizing: border-box; }
html, body { margin: 0; min-height: 100%; }
body {
  font-family: var(--sans);
  background:
    radial-gradient(1200px 500px at 10% -10%, #d9e6ff 0%, transparent 50%),
    radial-gradient(900px 400px at 100% 0%, #d7f3ea 0%, transparent 45%),
    var(--bg);
  color: var(--ink);
}
#app { min-height: 100vh; }
button { font-family: inherit; cursor: pointer; }
button:disabled { cursor: not-allowed; opacity: 0.45; }

.wrap {
  max-width: 1180px;
  margin: 0 auto;
  padding: 24px 20px 48px;
}

.mark {
  width: 44px;
  height: 44px;
  border-radius: 12px;
  background: var(--accent);
  color: #fff;
  display: grid;
  place-items: center;
  font-weight: 800;
  letter-spacing: -0.04em;
  font-size: 14px;
}

.hero {
  max-width: 640px;
  margin: 8vh auto 0;
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 24px;
  box-shadow: var(--shadow);
  padding: 40px;
}
.hero h1 { margin: 16px 0 8px; font-size: 32px; letter-spacing: -0.03em; }
.hero p { margin: 0 0 12px; color: var(--muted); line-height: 1.5; }
.meta-row { display: flex; flex-wrap: wrap; gap: 8px; margin: 22px 0 28px; }
.chip-meta {
  background: var(--accent-soft);
  color: var(--accent-ink);
  border-radius: 999px;
  padding: 6px 12px;
  font-size: 13px;
  font-weight: 600;
}

.primary, .ghost {
  border: 0;
  border-radius: 12px;
  padding: 12px 18px;
  font-size: 15px;
  font-weight: 650;
}
.primary { background: var(--accent); color: #fff; }
.primary:hover { background: var(--accent-ink); }
.ghost { background: var(--bg-2); color: var(--ink); }
.ghost:hover { background: var(--line); }
.btn-row { display: flex; gap: 10px; flex-wrap: wrap; }

.topbar {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 16px;
  margin-bottom: 14px;
}
.brand { display: flex; align-items: center; gap: 10px; }
.brand strong { display: block; font-size: 16px; }
.brand small { color: var(--muted); font-size: 12px; }
.top-actions { display: flex; align-items: center; gap: 8px; flex-wrap: wrap; }

.timer {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  background: #fff;
  border: 1px solid var(--line);
  border-radius: 999px;
  padding: 7px 12px;
  font-variant-numeric: tabular-nums;
  font-weight: 700;
}
.timer svg { width: 16px; height: 16px; }
.timer.low { color: var(--bad); border-color: #f5c2bc; background: var(--bad-bg); }

.progress {
  height: 8px;
  background: var(--line);
  border-radius: 99px;
  overflow: hidden;
  margin-bottom: 18px;
}
.progress > span {
  display: block;
  height: 100%;
  background: var(--accent);
}

.layout {
  display: grid;
  grid-template-columns: 220px 1fr;
  gap: 18px;
}
@media (max-width: 860px) {
  .layout { grid-template-columns: 1fr; }
}

.nav-card, .q-card, .score-card {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
}
.nav-card { padding: 14px; }
.nav-card h2 {
  margin: 0 0 10px;
  font-size: 12px;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--muted);
}
.grid {
  display: grid;
  grid-template-columns: repeat(5, 1fr);
  gap: 6px;
}
.nav-btn {
  border: 1px solid var(--line);
  background: #fff;
  border-radius: 8px;
  height: 34px;
  font-weight: 650;
  font-size: 13px;
  color: var(--ink);
}
.nav-btn.answered { background: var(--accent-soft); border-color: #e8c39a; color: var(--accent-ink); }
.nav-btn.flagged { background: var(--flag-bg); border-color: #f0c48a; }
.nav-btn.current { outline: 2px solid var(--accent); outline-offset: 1px; }
.nav-btn.ok { background: var(--ok-bg); border-color: #b7e3cb; color: var(--ok); }
.nav-btn.bad { background: var(--bad-bg); border-color: #f5c2bc; color: var(--bad); }
.legend { margin-top: 12px; font-size: 12px; color: var(--muted); }

.q-card { padding: 26px 28px 22px; min-height: 520px; display: flex; flex-direction: column; }
.q-kicker {
  color: var(--muted);
  font-size: 13px;
  font-weight: 700;
  letter-spacing: 0.04em;
  margin-bottom: 10px;
}
.stem {
  font-size: 20px;
  line-height: 1.45;
  margin: 0 0 20px;
  letter-spacing: -0.02em;
}
.stem code, .opt-text code, .chip {
  font-family: var(--mono);
  font-size: 0.86em;
  background: var(--bg-2);
  padding: 1px 6px;
  border-radius: 6px;
}
.options { display: flex; flex-direction: column; gap: 10px; flex: 1; }
.opt {
  display: grid;
  grid-template-columns: 36px 1fr;
  gap: 12px;
  align-items: start;
  border: 1px solid var(--line);
  border-radius: 12px;
  padding: 12px 14px;
  background: #fff;
  text-align: left;
}
.opt:hover { border-color: #9db7f0; }
.opt.picked { border-color: var(--accent); background: var(--accent-soft); }
.opt.reveal-ok { border-color: var(--ok); background: var(--ok-bg); }
.opt.reveal-bad { border-color: var(--bad); background: var(--bad-bg); }
.letter {
  width: 36px;
  height: 36px;
  border-radius: 10px;
  display: grid;
  place-items: center;
  font-weight: 800;
  background: var(--bg-2);
}
.opt.picked .letter { background: var(--accent); color: #fff; }
.opt.reveal-ok .letter { background: var(--ok); color: #fff; }
.opt.reveal-bad .letter { background: var(--bad); color: #fff; }
.opt-text { padding-top: 6px; line-height: 1.45; }
.opt-text pre {
  margin: 0;
  font-family: var(--mono);
  font-size: 12.5px;
  line-height: 1.4;
  white-space: pre-wrap;
  background: #0f1724;
  color: #e7eef8;
  padding: 12px;
  border-radius: 10px;
  overflow: auto;
}

.why {
  margin-top: 16px;
  padding: 12px 14px;
  border-radius: 12px;
  background: var(--ok-bg);
  color: #145c3d;
  line-height: 1.45;
}
.why.miss { background: var(--bad-bg); color: #7a241c; }

.q-actions {
  display: flex;
  justify-content: space-between;
  gap: 10px;
  margin-top: 22px;
  padding-top: 16px;
  border-top: 1px solid var(--line);
}
.flag {
  background: transparent;
  border: 1px dashed var(--line);
  color: var(--muted);
  border-radius: 12px;
  padding: 10px 14px;
  font-weight: 650;
}
.flag.on { background: var(--flag-bg); border-style: solid; border-color: #f0c48a; color: var(--flag); }

.score-card { padding: 32px; text-align: center; margin-top: 12px; }
.score-num {
  font-size: 72px;
  font-weight: 800;
  letter-spacing: -0.04em;
  line-height: 1;
  margin: 8px 0 4px;
}
.pass { color: var(--ok); }
.fail { color: var(--bad); }
.score-sub { color: var(--muted); margin-bottom: 18px; }
.breakdown {
  display: flex;
  justify-content: center;
  gap: 18px;
  margin: 8px 0 24px;
  font-weight: 650;
  color: var(--muted);
}
.filters { display: flex; justify-content: center; gap: 8px; margin-bottom: 18px; }
.filter {
  border: 1px solid var(--line);
  background: #fff;
  border-radius: 999px;
  padding: 7px 12px;
  font-weight: 650;
}
.filter.on { background: var(--ink); color: #fff; border-color: var(--ink); }
.review-list { text-align: left; display: flex; flex-direction: column; gap: 10px; }
.review-item {
  border: 1px solid var(--line);
  border-radius: 12px;
  padding: 14px 16px;
  cursor: pointer;
  background: #fff;
}
.review-item h3 { margin: 0 0 6px; font-size: 15px; }
.review-item p { margin: 0; color: var(--muted); font-size: 13px; }

.hint { margin-top: 14px; color: var(--muted); font-size: 12px; }
kbd {
  font-family: var(--mono);
  font-size: 11px;
  border: 1px solid var(--line);
  background: var(--bg);
  border-radius: 5px;
  padding: 1px 5px;
}

.modal-bg {
  position: fixed;
  inset: 0;
  background: rgba(15, 23, 36, 0.45);
  display: grid;
  place-items: center;
  padding: 20px;
  z-index: 20;
}
.modal {
  background: #fff;
  border-radius: 16px;
  padding: 24px;
  max-width: 420px;
  width: 100%;
  box-shadow: var(--shadow);
}
.modal.wide { max-width: 640px; }
.modal h2 { margin: 0 0 8px; }
.modal p { color: var(--muted); }
.note {
  width: 100%;
  min-height: 220px;
  font-family: var(--sans);
  font-size: 14px;
  padding: 10px;
  border: 1px solid var(--line);
  border-radius: 8px;
}
.calc { display: grid; grid-template-columns: repeat(4, 1fr); gap: 8px; }
.calc input {
  grid-column: 1 / -1;
  font-size: 22px;
  padding: 10px;
  text-align: right;
  font-variant-numeric: tabular-nums;
}
.calc button {
  padding: 12px;
  border: 1px solid var(--line);
  background: #f9fafb;
  border-radius: 8px;
  font-weight: 700;
}

.icon-btn { display: inline-flex; align-items: center; justify-content: center; width: 40px; padding: 10px; }
.icon-btn svg { width: 18px; height: 18px; }
.hero { position: relative; }
.theme-corner { position: absolute; top: 20px; right: 20px; }
.options-row { display: flex; flex-wrap: wrap; gap: 16px; margin: 4px 0 4px; }
.switch { display: flex; align-items: center; gap: 8px; font-size: 14px; color: var(--muted); cursor: pointer; }
.switch input { width: 16px; height: 16px; }
.hint-sub { margin: 0 0 18px; color: var(--muted); font-size: 12px; }
.shortcuts { list-style: none; margin: 0; padding: 0; display: flex; flex-direction: column; gap: 8px; color: var(--muted); font-size: 14px; }

.print-only { display: none; }

/* Dark mode */
:root[data-theme="dark"] {
  --bg: #0e1420;
  --bg-2: #172031;
  --card: #141c2c;
  --ink: #e7ecf6;
  --muted: #93a3bd;
  --line: #29344c;
  --accent: #e08a3e;
  --accent-ink: #f2b784;
  --accent-soft: #3a2716;
  --ok: #3fd08f;
  --ok-bg: #10301f;
  --bad: #ff7a72;
  --bad-bg: #3a1a1a;
  --flag: #f2b657;
  --flag-bg: #3a2c10;
  --shadow: 0 10px 30px rgba(0, 0, 0, 0.5);
}
:root[data-theme="dark"] body {
  background:
    radial-gradient(1200px 500px at 10% -10%, #17223a 0%, transparent 50%),
    radial-gradient(900px 400px at 100% 0%, #103428 0%, transparent 45%),
    var(--bg);
}
:root[data-theme="dark"] .nav-btn,
:root[data-theme="dark"] .opt,
:root[data-theme="dark"] .filter,
:root[data-theme="dark"] .review-item,
:root[data-theme="dark"] .timer {
  background: var(--card);
  color: var(--ink);
}
:root[data-theme="dark"] .review-item p { color: var(--muted); }
:root[data-theme="dark"] .calc button { background: #1b2438; color: var(--ink); }
:root[data-theme="dark"] .calc input { background: #10182a; color: var(--ink); border-color: var(--line); }
:root[data-theme="dark"] .note { background: #10182a; color: var(--ink); border-color: var(--line); }
:root[data-theme="dark"] .modal { background: var(--card); color: var(--ink); }
:root[data-theme="dark"] .modal p { color: var(--muted); }

/* Print */
@media print {
  body { background: #fff; }
  .topbar, .nav-card, .progress, .no-print, .hero .btn-row, .hero .hint, .hero .options-row, .hero .hint-sub {
    display: none !important;
  }
  .wrap { max-width: 100%; padding: 0; }
  .score-card { box-shadow: none; border: none; padding: 0; }
  .print-only { display: block !important; margin-top: 6px; }
  .print-stem { font-weight: 650; color: #000; }
  .print-why { color: #333; }
  .review-item { break-inside: avoid; border: none; border-bottom: 1px solid #ccc; border-radius: 0; padding: 12px 0; }
}