* { box-sizing: border-box; margin: 0; padding: 0; }
:root {
  --brand: #1a7f4b;
  --brand-light: #e8f5ee;
  --danger: #c0392b;
  --danger-light: #fdeeec;
  --line: #e3e6ea;
  --text: #24292f;
  --muted: #6a737d;
  --bg: #f5f6f8;
}
body {
  font-family: "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.65;
}
#app { max-width: 880px; margin: 0 auto; padding: 16px 16px 60px; }

/* ===== 首页 ===== */
.hero { text-align: center; padding: 36px 0 20px; }
.hero h1 { font-size: 30px; letter-spacing: 2px; }
.hero p { color: var(--muted); margin-top: 8px; font-size: 14px; }
.subject-card {
  background: #fff; border: 1px solid var(--line); border-radius: 12px;
  padding: 20px 22px; margin-top: 16px;
  box-shadow: 0 1px 3px rgba(0,0,0,.04);
}
.subject-card h2 { font-size: 19px; }
.subject-stats { display: flex; gap: 18px; flex-wrap: wrap; color: var(--muted); font-size: 13.5px; margin-top: 6px; }
.subject-stats b { color: var(--text); }
.btn-row { display: flex; gap: 10px; margin-top: 14px; flex-wrap: wrap; }
button { cursor: pointer; font-family: inherit; }
.btn {
  border: 1px solid var(--line); background: #fff; color: var(--text);
  border-radius: 8px; padding: 8px 16px; font-size: 14.5px; transition: all .15s;
}
.btn:hover { border-color: var(--brand); color: var(--brand); }
.btn.primary { background: var(--brand); border-color: var(--brand); color: #fff; }
.btn.primary:hover { filter: brightness(1.08); color: #fff; }
.btn.danger-text:hover { border-color: var(--danger); color: var(--danger); }
.btn:disabled { opacity: .45; cursor: not-allowed; pointer-events: none; }
.link-muted { background: none; border: none; color: var(--muted); font-size: 13px; text-decoration: underline; }

/* ===== 答题页 ===== */
.topbar {
  position: sticky; top: 0; z-index: 10; background: #fff; border-bottom: 1px solid var(--line);
  margin: 0 -16px 14px; padding: 10px 16px;
  display: flex; align-items: center; gap: 12px; flex-wrap: wrap;
}
.topbar .title { font-weight: 600; font-size: 15.5px; }
.topbar .pos { color: var(--muted); font-size: 13.5px; }
.topbar .counters { margin-left: auto; display: flex; gap: 12px; font-size: 13.5px; }
.counters .ok { color: var(--brand); font-weight: 600; }
.counters .bad { color: var(--danger); font-weight: 600; }
.progress { height: 5px; background: var(--line); border-radius: 3px; overflow: hidden; margin: 0 -16px 16px; }
.progress > div { height: 100%; background: var(--brand); transition: width .25s; }

.q-card { background: #fff; border: 1px solid var(--line); border-radius: 12px; padding: 22px 24px; }
.type-badge {
  display: inline-block; font-size: 12.5px; color: var(--brand); background: var(--brand-light);
  border-radius: 20px; padding: 2px 12px; margin-bottom: 12px;
}
.group-box {
  background: #fafbfc; border: 1px dashed #d5d9de; border-radius: 8px;
  padding: 12px 16px; margin-bottom: 14px; font-size: 14.5px;
}
.group-box .gb-title { font-size: 13px; color: var(--muted); margin-bottom: 6px; }
.group-box.material { font-family: "Kaiti SC", "STKaiti", KaiTi, serif; font-size: 15.5px; }
.stem { font-size: 17px; font-weight: 600; margin-bottom: 16px; }
.opts { display: flex; flex-direction: column; gap: 10px; }
.opt {
  text-align: left; border: 1.5px solid var(--line); background: #fff; border-radius: 9px;
  padding: 11px 15px; font-size: 15.5px; line-height: 1.55; transition: all .12s;
  display: flex; gap: 10px;
}
.opt .tag { font-weight: 700; flex: none; }
.opt:hover { border-color: var(--brand); background: #fafcfb; }
.opt.selected { border-color: var(--brand); background: var(--brand-light); }
.opt.correct { border-color: var(--brand); background: var(--brand-light); }
.opt.correct .tag::after { content: " ✓"; color: var(--brand); }
.opt.wrong { border-color: var(--danger); background: var(--danger-light); }
.opt.wrong .tag::after { content: " ✗"; color: var(--danger); }
.opt:disabled { cursor: default; }
.opt:disabled:not(.correct):not(.wrong):hover { border-color: var(--line); background: #fff; }

.feedback { margin-top: 18px; border-radius: 9px; padding: 14px 16px; font-size: 15px; }
.feedback.right { background: var(--brand-light); border: 1px solid #bfe3cf; }
.feedback.wrongfb { background: var(--danger-light); border: 1px solid #f2c4bd; }
.feedback .verdict { font-weight: 700; font-size: 15.5px; }
.feedback.right .verdict { color: var(--brand); }
.feedback.wrongfb .verdict { color: var(--danger); }
.feedback .exp { margin-top: 8px; color: #444; }
.nav-row { display: flex; gap: 10px; margin-top: 20px; align-items: center; }
.nav-row .spacer { flex: 1; }
.redo-link { margin-left: auto; }

/* ===== 答题卡 ===== */
.sheet-mask { position: fixed; inset: 0; background: rgba(0,0,0,.35); display: flex; align-items: center; justify-content: center; z-index: 50; }
.sheet { background: #fff; border-radius: 12px; padding: 20px 22px; width: min(680px, 92vw); max-height: 82vh; overflow: auto; }
.sheet h3 { margin-bottom: 12px; }
.sheet-grid { display: grid; grid-template-columns: repeat(10, 1fr); gap: 7px; }
.cell {
  aspect-ratio: 1; border: 1px solid var(--line); border-radius: 6px; background: #fff;
  font-size: 13px; display: flex; align-items: center; justify-content: center;
}
.cell:hover { border-color: var(--brand); }
.cell.done-ok { background: var(--brand); border-color: var(--brand); color: #fff; }
.cell.done-bad { background: var(--danger); border-color: var(--danger); color: #fff; }
.cell.cur { outline: 2.5px solid #f0a30a; outline-offset: 1px; }
.sheet-legend { margin-top: 12px; font-size: 13px; color: var(--muted); display: flex; gap: 16px; flex-wrap: wrap; }
.sheet-close { margin-top: 14px; text-align: center; }

/* ===== 完成页 ===== */
.done-card { background: #fff; border: 1px solid var(--line); border-radius: 12px; padding: 40px 24px; text-align: center; }
.done-card .big { font-size: 44px; font-weight: 700; }
.done-card p { color: var(--muted); margin-top: 6px; }

@media (max-width: 640px) {
  .q-card { padding: 16px 14px; }
  .sheet-grid { grid-template-columns: repeat(8, 1fr); }
}