:root {
  --primary: #2563eb;
  --primary-dark: #1e40af;
  --bg: #f5f7fb;
  --card: #ffffff;
  --text: #1f2937;
  --muted: #6b7280;
  --green: #16a34a;
  --red: #dc2626;
  --radius: 12px;
}
* { box-sizing: border-box; margin: 0; padding: 0; }
body {
  font-family: -apple-system, "PingFang SC", "Microsoft YaHei", "Segoe UI", sans-serif;
  background: var(--bg); color: var(--text); line-height: 1.6;
}
#app { max-width: 760px; margin: 0 auto; min-height: 100vh; display: flex; flex-direction: column; }
.topbar {
  position: sticky; top: 0; z-index: 10; background: var(--primary); color: #fff;
  padding: 12px 16px; display: flex; align-items: baseline; gap: 10px;
  box-shadow: 0 2px 8px rgba(0,0,0,.15);
}
.topbar h1 { font-size: 17px; font-weight: 600; }
.topbar .sub { font-size: 12px; opacity: .85; margin-left: auto; }
.topbar .back { font-size: 15px; cursor: pointer; user-select: none; }
main { flex: 1; padding: 14px; }

/* home */
.stats { display: grid; grid-template-columns: repeat(4, 1fr); gap: 10px; margin-bottom: 14px; }
.stat { background: var(--card); border-radius: var(--radius); padding: 12px; text-align: center; box-shadow: 0 1px 3px rgba(0,0,0,.06); }
.stat b { font-size: 20px; color: var(--primary); display: block; }
.stat span { font-size: 12px; color: var(--muted); }
.modes { display: grid; grid-template-columns: repeat(auto-fill, minmax(112px, 1fr)); gap: 10px; margin-bottom: 16px; }
.mode-card {
  background: var(--card); border-radius: var(--radius); padding: 14px; cursor: pointer;
  box-shadow: 0 1px 3px rgba(0,0,0,.06); transition: transform .1s;
}
.mode-card:active { transform: scale(.97); }
.mode-card .icon { font-size: 22px; }
.mode-card .name { font-weight: 600; font-size: 14px; margin-top: 4px; }
.mode-card .desc { font-size: 11px; color: var(--muted); }
.section-title { font-size: 14px; font-weight: 600; color: var(--muted); margin: 14px 0 8px; }
.exam-list { display: grid; grid-template-columns: repeat(auto-fill, minmax(150px, 1fr)); gap: 8px; }
.exam-item {
  background: var(--card); border-radius: 10px; padding: 10px 12px; cursor: pointer; font-size: 13px;
  box-shadow: 0 1px 3px rgba(0,0,0,.06); display: flex; justify-content: space-between; align-items: center;
}
.exam-item .cnt { font-size: 11px; color: var(--muted); }
.exam-item .done { color: var(--green); font-size: 11px; }

/* question */
.qcard { background: var(--card); border-radius: var(--radius); padding: 18px 16px; box-shadow: 0 1px 3px rgba(0,0,0,.06); }
.qmeta { display: flex; gap: 8px; align-items: center; margin-bottom: 10px; flex-wrap: wrap; }
.tag { font-size: 11px; padding: 2px 8px; border-radius: 999px; background: #eef2ff; color: var(--primary-dark); }
.tag.type { background: #fef3c7; color: #92400e; }
.progress-txt { margin-left: auto; font-size: 12px; color: var(--muted); }
.qstem { font-size: 16px; margin-bottom: 14px; white-space: pre-wrap; }
.opt {
  display: flex; gap: 10px; align-items: flex-start; padding: 10px 12px; margin-bottom: 8px;
  border: 1.5px solid #e5e7eb; border-radius: 10px; cursor: pointer; font-size: 14px; background:#fff;
}
.opt:hover { border-color: var(--primary); }
.opt .key { font-weight: 700; color: var(--muted); flex-shrink: 0; }
.opt.picked { border-color: var(--primary); background: #eff6ff; }
.opt.correct { border-color: var(--green); background: #f0fdf4; }
.opt.wrong { border-color: var(--red); background: #fef2f2; }
.opt.disabled { pointer-events: none; opacity: .92; }
.feedback { margin-top: 12px; border-radius: 10px; padding: 12px; font-size: 13px; }
.feedback.ok { background: #f0fdf4; border: 1px solid #bbf7d0; }
.feedback.no { background: #fef2f2; border: 1px solid #fecaca; }
.feedback .verdict { font-weight: 700; margin-bottom: 4px; }
.feedback .ana { color: var(--text); }
.subjective-answer { margin-top: 12px; background: #f8fafc; border: 1px solid #e2e8f0; border-radius: 10px; padding: 12px; font-size: 14px; white-space: pre-wrap; }
.actions { display: flex; gap: 10px; margin-top: 14px; flex-wrap: wrap; }
.btn {
  border: none; border-radius: 10px; padding: 10px 18px; font-size: 14px; cursor: pointer;
  background: var(--primary); color: #fff; font-weight: 500;
}
.btn:active { background: var(--primary-dark); }
.btn.ghost { background: #fff; color: var(--primary); border: 1.5px solid var(--primary); }
.btn.gray { background: #e5e7eb; color: var(--text); }
.btn.green { background: var(--green); }
.btn.red { background: var(--red); }
.btn.wide { width: 100%; }
.hint { font-size: 12px; color: var(--muted); margin-top: 10px; }

/* result */
.result { text-align: center; padding: 30px 10px; }
.result .big { font-size: 42px; font-weight: 700; color: var(--primary); }
.result .lbl { color: var(--muted); margin-bottom: 18px; }
.result .rows { display: flex; justify-content: center; gap: 24px; margin-bottom: 22px; flex-wrap: wrap; }
.result .rows div b { display: block; font-size: 22px; }
.result .rows div span { font-size: 12px; color: var(--muted); }

/* search */
.searchbar { display: flex; gap: 8px; margin-bottom: 12px; }
.searchbar input {
  flex: 1; border: 1.5px solid #d1d5db; border-radius: 10px; padding: 10px 12px; font-size: 14px; outline: none;
}
.searchbar input:focus { border-color: var(--primary); }
.sres { background: var(--card); border-radius: 10px; padding: 12px; margin-bottom: 8px; cursor: pointer; box-shadow: 0 1px 3px rgba(0,0,0,.05); font-size: 14px; }
.sres .meta { font-size: 11px; color: var(--muted); margin-bottom: 2px; }
mark { background: #fde68a; padding: 0 1px; }

/* flashcards */
.deck-list { display: grid; grid-template-columns: repeat(auto-fill, minmax(200px, 1fr)); gap: 10px; }
.deck {
  background: var(--card); border-radius: var(--radius); padding: 14px; cursor: pointer;
  box-shadow: 0 1px 3px rgba(0,0,0,.06); display: flex; align-items: center; gap: 10px;
  border: 1.5px solid transparent; transition: border-color .12s;
}
.deck:hover { border-color: var(--primary); }
.deck .dicon { font-size: 22px; }
.deck .dname { font-weight: 600; font-size: 14px; }
.deck .dnum { margin-left: auto; font-size: 11px; color: var(--muted); text-align: right; }
.flash-card { animation: cardin .22s ease-out; }
.flash-card.is-flipped { border: 1.5px solid #bfdbfe; }
@keyframes cardin { from { opacity: 0; transform: translateY(8px) rotateX(-6deg); } to { opacity: 1; transform: none; } }
#cRate .btn { flex: 1; }
#clrCard { color: var(--primary); cursor: pointer; }

/* recite card */
.recite-flip { text-align: center; color: var(--muted); font-size: 13px; margin-top: 14px; }
.empty { text-align: center; color: var(--muted); padding: 40px 0; font-size: 14px; }
@media (max-width: 480px) {
  .qstem { font-size: 15px; }
  .stats { grid-template-columns: repeat(2, 1fr); }
  .exam-list, .modes { grid-template-columns: repeat(2, 1fr); }
}