:root {
  --bg: #f5f6f8;
  --card: #ffffff;
  --ink: #1f2733;
  --muted: #6b7280;
  --line: #e5e7eb;
  --primary: #2563eb;
  --primary-d: #1d4ed8;
  --ok: #16a34a;
  --ok-bg: #ecfdf3;
  --bad: #dc2626;
  --bad-bg: #fef2f2;
  --warn: #d97706;
  --shadow: 0 1px 3px rgba(0,0,0,.08), 0 4px 16px rgba(0,0,0,.04);
}
* { box-sizing: border-box; }
body {
  margin: 0;
  font-family: -apple-system, "Segoe UI", "Microsoft YaHei", Roboto, sans-serif;
  background: var(--bg);
  color: var(--ink);
  line-height: 1.6;
}
.topbar {
  display: flex; align-items: center; justify-content: space-between;
  padding: 12px 20px; background: var(--card); border-bottom: 1px solid var(--line);
  position: sticky; top: 0; z-index: 10;
}
.brand { font-size: 19px; font-weight: 700; }
.brand .sub { font-size: 12px; color: var(--muted); font-weight: 400; margin-left: 6px; }
nav .nav-btn {
  border: none; background: transparent; color: var(--muted);
  font-size: 15px; padding: 8px 14px; cursor: pointer; border-radius: 8px; margin-left: 4px;
}
nav .nav-btn.active { color: var(--primary); background: #eef2ff; font-weight: 600; }
main { max-width: 860px; margin: 0 auto; padding: 20px; }
.view { display: none; }
.view.active { display: block; }
.hidden { display: none !important; }

.card {
  background: var(--card); border: 1px solid var(--line); border-radius: 12px;
  padding: 18px 20px; box-shadow: var(--shadow); margin-bottom: 16px;
}
.card h3 { margin: 0 0 14px; font-size: 16px; }

/* 题型筛选 + 步骤标签 */
.filter-block { margin-bottom: 18px; }
.step-label { font-size: 13px; color: var(--muted); font-weight: 600; margin-bottom: 10px; letter-spacing: .5px; }
.chips { display: flex; flex-wrap: wrap; gap: 10px; }
.chip {
  border: 1px solid var(--line); background: #fff; color: var(--ink);
  padding: 8px 18px; border-radius: 99px; font-size: 14px; cursor: pointer; transition: .15s;
}
.chip:hover { border-color: var(--primary); }
.chip.active { background: var(--primary); border-color: var(--primary); color: #fff; font-weight: 600; }

/* 模式卡片 */
.mode-grid { display: grid; grid-template-columns: repeat(2, 1fr); gap: 14px; }
.mode-card {
  background: var(--card); border: 1px solid var(--line); border-radius: 12px;
  padding: 20px; cursor: pointer; box-shadow: var(--shadow); transition: .15s;
  display: flex; flex-direction: column; gap: 6px;
}
.mode-card:hover { transform: translateY(-2px); border-color: var(--primary); }
.mode-card .ico { font-size: 26px; }
.mode-card .t { font-size: 17px; font-weight: 700; }
.mode-card .d { font-size: 13px; color: var(--muted); }

/* 表单 */
.row { margin-bottom: 12px; display: flex; flex-direction: column; gap: 4px; }
.row label { font-size: 13px; color: var(--muted); }
input, select, textarea {
  border: 1px solid var(--line); border-radius: 8px; padding: 9px 10px;
  font-size: 14px; font-family: inherit; background: #fff; color: var(--ink); width: 100%;
}
textarea { resize: vertical; }
.actions { display: flex; gap: 10px; flex-wrap: wrap; }

.btn {
  border: 1px solid var(--line); background: #fff; color: var(--ink);
  padding: 9px 16px; border-radius: 8px; font-size: 14px; cursor: pointer; transition: .15s;
}
.btn.primary { background: var(--primary); border-color: var(--primary); color: #fff; }
.btn.primary:hover { background: var(--primary-d); }
.btn.ghost { background: #fff; }
.btn.ghost:hover { border-color: var(--primary); color: var(--primary); }
.btn.danger { color: var(--bad); border-color: #fecaca; }
.btn.danger:hover { background: var(--bad-bg); }
.msg { font-size: 13px; color: var(--muted); margin-left: 8px; }
.msg.ok { color: var(--ok); }
.msg.err { color: var(--bad); }

/* 答题 */
.progress-wrap { display: flex; align-items: center; gap: 10px; flex: 1; }
.progress-bar { flex: 1; height: 8px; background: #eef0f3; border-radius: 99px; overflow: hidden; }
#progress-fill { height: 100%; width: 0; background: var(--primary); transition: .2s; }
#progress-text { font-size: 13px; color: var(--muted); white-space: nowrap; }
.timer { font-size: 14px; font-weight: 600; color: var(--warn); background: #fffbeb; padding: 4px 10px; border-radius: 8px; }
.quiz-head { display: flex; align-items: center; gap: 14px; margin-bottom: 14px; }
#quiz-body .q-meta { font-size: 12px; color: var(--muted); margin-bottom: 8px; }
#quiz-body .q-stem { font-size: 17px; font-weight: 600; margin-bottom: 16px; white-space: pre-wrap; }
.opt {
  display: flex; align-items: center; gap: 10px; border: 1px solid var(--line);
  border-radius: 10px; padding: 12px 14px; margin-bottom: 10px; cursor: pointer; transition: .12s; background: #fff;
}
.opt:hover { border-color: var(--primary); }
.opt .badge {
  width: 26px; height: 26px; border-radius: 50%; border: 1px solid var(--line);
  display: flex; align-items: center; justify-content: center; font-weight: 700; flex: 0 0 26px; color: var(--muted);
}
.opt.selected { border-color: var(--primary); background: #eef2ff; }
.opt.correct { border-color: var(--ok); background: var(--ok-bg); }
.opt.wrong { border-color: var(--bad); background: var(--bad-bg); }
.opt .text { white-space: pre-wrap; }
.analysis { margin-top: 14px; padding: 12px 14px; background: #f8fafc; border-left: 3px solid var(--primary); border-radius: 6px; font-size: 14px; }
.analysis .h { font-weight: 700; color: var(--primary); margin-bottom: 4px; }
.feedback { font-weight: 700; margin: 10px 0; }
.feedback.ok { color: var(--ok); }
.feedback.bad { color: var(--bad); }

.quiz-actions { display: flex; gap: 10px; justify-content: flex-end; margin-top: 4px; }
.quiz-actions.center { justify-content: center; }

/* 结果 */
#result-body { text-align: center; }
.score-big { font-size: 46px; font-weight: 800; color: var(--primary); margin: 8px 0; }
.stat-row { display: flex; justify-content: center; gap: 26px; flex-wrap: wrap; margin: 14px 0; }
.stat-row .s { font-size: 14px; color: var(--muted); }
.stat-row .s b { display: block; font-size: 22px; color: var(--ink); }

/* 题库列表 */
.list-head { display: flex; align-items: center; justify-content: space-between; flex-wrap: wrap; gap: 10px; }
.q-list { max-height: 420px; overflow: auto; margin-top: 12px; }
.q-item { border: 1px solid var(--line); border-radius: 10px; padding: 10px 12px; margin-bottom: 8px; }
.q-item .qt { font-weight: 600; font-size: 14px; display: flex; gap: 8px; align-items: center; }
.q-item .tag { font-size: 11px; padding: 2px 8px; border-radius: 99px; background: #eef2ff; color: var(--primary); }
.q-item .tag.multiple { background: #fef3c7; color: #b45309; }
.q-item .tag.judge { background: #dcfce7; color: #15803d; }
.q-item .qa { font-size: 12px; color: var(--muted); margin-top: 4px; }

/* 后台：题库卡片 */
.bank-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(220px, 1fr)); gap: 14px; margin-top: 4px; }
.bank-card {
  background: var(--card); border: 1px solid var(--line); border-radius: 12px;
  padding: 16px; box-shadow: var(--shadow); display: flex; flex-direction: column; gap: 10px;
}
.bank-card .bc-name { font-size: 16px; font-weight: 700; word-break: break-all; line-height: 1.4; }
.bank-card .bc-meta { font-size: 13px; color: var(--muted); }
.bank-card .bc-actions { display: flex; gap: 8px; }
.bank-card .bc-actions .btn { flex: 1; justify-content: center; padding: 8px; font-size: 13px; }
.q-item .del { float: right; color: var(--bad); cursor: pointer; font-size: 13px; }

.review-item { border: 1px solid var(--line); border-radius: 10px; padding: 14px; margin-bottom: 12px; }
.review-item.wrong { border-color: #fecaca; }
.review-item.correct { border-color: #bbf7d0; }

@media (max-width: 600px) {
  .mode-grid { grid-template-columns: 1fr; }
  main { padding: 14px; }
}