:root {
  --bg: #f5f7fb;
  --card: #ffffff;
  --text: #1f2937;
  --muted: #6b7280;
  --line: #dbe3ee;
  --primary: #1d4ed8;
  --primary-soft: #dbeafe;
  --ok: #166534;
  --ok-bg: #dcfce7;
  --bad: #991b1b;
  --bad-bg: #fee2e2;
}
* { box-sizing: border-box; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'PingFang SC', 'Microsoft YaHei', sans-serif;
}
.wrap { width: min(1020px, calc(100% - 32px)); margin: 0 auto; }
.topbar { background: #0f172a; color: #fff; }
.nav { display: flex; justify-content: space-between; align-items: center; padding: 16px 0; gap: 12px; }
.nav a { color: #cbd5e1; text-decoration: none; margin-left: 18px; }
.brand { font-weight: 700; }
main.wrap { padding: 24px 0 48px; }
.card {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 16px;
  padding: 22px;
  box-shadow: 0 8px 24px rgba(15, 23, 42, 0.04);
  margin-bottom: 20px;
}
.narrow { max-width: 720px; }
.hero h1, .card h1, .card h2 { margin-top: 0; }
.stats-grid, .grid.two { display: grid; gap: 16px; }
.stats-grid { grid-template-columns: repeat(3, 1fr); margin: 18px 0; }
.grid.two { grid-template-columns: repeat(2, 1fr); }
.stat, .score-board.boxed {
  background: #f8fafc;
  border-radius: 14px;
  padding: 18px;
  border: 1px solid var(--line);
}
.num { display: block; font-size: 28px; font-weight: 800; }
.label { color: var(--muted); }
.actions { display: flex; gap: 12px; flex-wrap: wrap; margin-top: 16px; align-items: center; }
.actions.spaced { justify-content: space-between; }
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 10px 16px;
  border-radius: 10px;
  border: 1px solid var(--line);
  background: #fff;
  color: var(--text);
  text-decoration: none;
  cursor: pointer;
  font-size: 14px;
}
.btn.primary {
  background: var(--primary);
  color: #fff;
  border-color: var(--primary);
}
.btn.danger {
  background: #fff5f5;
  color: var(--bad);
  border-color: #fecaca;
}
.flash-stack { margin-bottom: 18px; display: grid; gap: 10px; }
.flash, .inline-flash {
  padding: 12px 14px;
  border-radius: 10px;
  border: 1px solid var(--line);
}
.flash.success, .inline-flash.success { background: var(--ok-bg); color: var(--ok); border-color: #86efac; }
.flash.error { background: var(--bad-bg); color: var(--bad); border-color: #fca5a5; }
.filter-grid {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 12px;
}
select, input[type="file"], textarea {
  width: 100%;
  padding: 10px 12px;
  border: 1px solid var(--line);
  border-radius: 10px;
  background: #fff;
}
.question-card .stem, .result-card .stem {
  font-size: 19px;
  line-height: 1.75;
  margin: 18px 0;
}
.meta-row { display: flex; gap: 10px; flex-wrap: wrap; }
.tag {
  display: inline-block;
  padding: 6px 10px;
  border-radius: 999px;
  background: var(--primary-soft);
  color: var(--primary);
  font-size: 13px;
}
.options { display: grid; gap: 12px; margin: 18px 0; }
.option-row {
  display: flex;
  gap: 10px;
  align-items: flex-start;
  padding: 12px 14px;
  border: 1px solid var(--line);
  border-radius: 12px;
  background: #fcfdff;
}
.option-row input { margin-top: 4px; }
.note {
  border-left: 4px solid #93c5fd;
  background: #eff6ff;
  padding: 12px 14px;
  border-radius: 8px;
}
.note.subtle { margin-bottom: 12px; }
.simple-list { list-style: none; padding: 0; margin: 0; }
.simple-list li {
  display: flex;
  justify-content: space-between;
  padding: 10px 0;
  border-bottom: 1px solid var(--line);
}
.score-board {
  display: flex;
  gap: 20px;
  flex-wrap: wrap;
  margin-bottom: 16px;
  color: var(--muted);
}
.answer-panel {
  border-radius: 14px;
  padding: 16px;
  border: 1px solid var(--line);
  margin: 18px 0;
}
.answer-panel.ok { background: var(--ok-bg); border-color: #86efac; }
.answer-panel.bad { background: var(--bad-bg); border-color: #fca5a5; }
.resume-box {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 12px;
}
.restart-form { margin-top: 16px; }
.history-list { display: grid; gap: 12px; }
.history-item {
  border: 1px solid var(--line);
  border-radius: 12px;
  padding: 14px;
}
.history-item.ok { background: #f0fdf4; }
.history-item.bad { background: #fff7ed; }
.history-title { font-weight: 700; margin-bottom: 6px; }
.history-stem { margin-bottom: 10px; color: var(--text); }
@media (max-width: 820px) {
  .stats-grid, .grid.two, .filter-grid { grid-template-columns: 1fr; }
  .resume-box, .nav { flex-direction: column; align-items: stretch; }
  .actions.spaced { justify-content: flex-start; }
}