:root{
  --bg:#f6f7fb;
  --card:#ffffff;
  --text:#1f2937;
  --muted:#6b7280;
  --line:#e5e7eb;
  --brand:#2563eb;
  --brand-soft:#eff6ff;
  --ok:#16a34a;
  --bad:#dc2626;
  --warn:#f59e0b;
  --shadow:0 10px 30px rgba(15,23,42,.06);
  --radius:18px;
}

*{box-sizing:border-box}
html,body{margin:0;padding:0;background:var(--bg);color:var(--text);font-family:system-ui,-apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,"PingFang SC","Hiragino Sans GB","Microsoft YaHei",sans-serif;line-height:1.55}
img{max-width:100%;display:block}

.topbar{
  position:sticky;top:0;z-index:10;
  background:rgba(246,247,251,.88);
  backdrop-filter:blur(10px);
  border-bottom:1px solid rgba(229,231,235,.8);
}
.topbar__inner{
  max-width:1200px;margin:0 auto;padding:18px 20px;
  display:flex;align-items:flex-start;justify-content:space-between;gap:16px;
}
h1{margin:0;font-size:24px}
.meta{margin:6px 0 0;color:var(--muted);font-size:14px}
.stats{
  display:grid;grid-auto-flow:column;gap:10px;align-items:center;
}
.stat{
  min-width:96px;padding:10px 12px;border:1px solid var(--line);border-radius:14px;background:#fff;
  box-shadow:var(--shadow);text-align:center
}
.stat strong{display:block;font-size:18px}
.stat span{font-size:12px;color:var(--muted)}

.page{max-width:1200px;margin:0 auto;padding:20px}
.card{
  background:var(--card);border:1px solid var(--line);border-radius:var(--radius);
  box-shadow:var(--shadow);
}
.intro{padding:18px 20px;margin-bottom:18px}
.intro h2{margin:0 0 8px;font-size:18px}
.intro p{margin:6px 0;color:var(--muted)}
.hint code{background:#f3f4f6;padding:2px 6px;border-radius:6px}

.section{
  margin-top:18px;
}
.section__head{
  display:flex;align-items:baseline;justify-content:space-between;gap:12px;
  margin:0 0 12px;
}
.section__title{
  margin:0;font-size:20px;
}
.section__count{
  color:var(--muted);font-size:13px;
}
.question-list{
  display:grid;gap:14px;
}

.question{
  padding:16px 16px 14px;
}
.question__top{
  display:flex;justify-content:space-between;gap:12px;align-items:flex-start;margin-bottom:10px;
}
.question__id{
  font-weight:700;font-size:15px;
}
.question__score{
  flex:none;white-space:nowrap;font-size:12px;color:var(--brand);background:var(--brand-soft);border:1px solid #dbeafe;padding:4px 8px;border-radius:999px;
}
.question__stem{
  margin:0 0 12px;font-size:15px;white-space:pre-wrap;word-break:break-word;
}
.question__image,
.answer__image{
  margin:10px 0;border:1px solid var(--line);border-radius:14px;overflow:hidden;background:#fafafa;
}
.question__image img,
.answer__image img{width:100%;height:auto}

.options{
  display:grid;gap:10px;margin:10px 0 14px;
}
.option{
  border:1px solid var(--line);border-radius:14px;padding:10px 12px;background:#fff;display:flex;gap:10px;align-items:flex-start;cursor:pointer;
}
.option input{margin-top:4px}
.option:hover{border-color:#cbd5e1;background:#fafcff}
.option.is-correct{border-color:rgba(22,163,74,.45);background:rgba(22,163,74,.06)}
.option.is-wrong{border-color:rgba(220,38,38,.45);background:rgba(220,38,38,.06)}
.option.is-selected{box-shadow:inset 0 0 0 1px rgba(37,99,235,.2)}

.controls{
  display:flex;flex-wrap:wrap;gap:10px;align-items:center;
}
button{
  appearance:none;border:none;border-radius:12px;padding:10px 14px;font-size:14px;font-weight:600;cursor:pointer;
}
.btn-primary{background:var(--brand);color:#fff}
.btn-primary:hover{filter:brightness(.96)}
.btn-ghost{background:#eef2ff;color:#3730a3}
.btn-ghost:hover{filter:brightness(.97)}
.btn-primary:disabled,.btn-ghost:disabled{cursor:not-allowed;opacity:.65}

.result{
  margin-top:12px;padding:12px 14px;border-radius:14px;border:1px solid var(--line);background:#fafafa
}
.result strong{display:block;margin-bottom:4px}
.result .ok{color:var(--ok);font-weight:700}
.result .bad{color:var(--bad);font-weight:700}
.result .answer-text{white-space:pre-wrap;word-break:break-word}

.blank-group{
  display:grid;gap:10px;margin:10px 0 14px;
}
.blank{
  width:100%;padding:11px 12px;border:1px solid var(--line);border-radius:12px;font-size:14px;background:#fff;
}
.blank:focus{outline:2px solid rgba(37,99,235,.18);border-color:#93c5fd}

.subjective-answer{
  margin-top:12px;padding:14px;border-radius:14px;border:1px solid rgba(37,99,235,.18);background:#f8fbff
}
.subjective-answer .label{
  display:inline-block;margin-bottom:8px;padding:4px 8px;border-radius:999px;background:#dbeafe;color:#1d4ed8;font-size:12px;font-weight:700;
}

.answer-block{
  margin-top:12px;
}

.small-muted{color:var(--muted);font-size:13px}

@media (max-width: 768px){
  .topbar__inner{flex-direction:column}
  .stats{grid-auto-flow:row;grid-template-columns:repeat(2,minmax(0,1fr));width:100%}
  .stat{min-width:auto}
  .question__top{flex-direction:column}
}