:root {
  --primary: #2b6cb0;
  --primary-dark: #1e4e8c;
  --bg: #f2f5f9;
  --card: #ffffff;
  --text: #1f2937;
  --muted: #6b7280;
  --ok: #16a34a;
  --ok-bg: #e8f8ee;
  --ng: #dc2626;
  --ng-bg: #fdecec;
  --radius: 14px;
}

* { box-sizing: border-box; margin: 0; padding: 0; -webkit-tap-highlight-color: transparent; }

html, body { height: 100%; }

body {
  font-family: -apple-system, BlinkMacSystemFont, "PingFang SC", "Microsoft YaHei", "Segoe UI", sans-serif;
  background: var(--bg);
  color: var(--text);
  font-size: 16px;
  line-height: 1.55;
}

.app {
  max-width: 560px;
  margin: 0 auto;
  min-height: 100dvh;
  display: flex;
  flex-direction: column;
  background: var(--bg);
  position: relative;
}

.hidden { display: none !important; }

/* ---------- 屏幕 ---------- */
.screen {
  flex: 1;
  overflow-y: auto;
  padding: 16px 16px 76px;
}

/* ---------- 首页 ---------- */
.home-header { text-align: center; padding: 18px 0 10px; }
.home-header h1 { color: var(--primary-dark); font-size: 24px; }
.home-header .sub { color: var(--muted); font-size: 13px; margin-top: 6px; }

.count-row {
  display: flex; align-items: center; gap: 10px;
  margin: 10px 0 16px;
}
.count-label { font-size: 14px; color: var(--muted); white-space: nowrap; }
.seg { display: flex; background: #e2e8f0; border-radius: 10px; padding: 3px; flex: 1; }
.seg-btn {
  flex: 1; border: 0; background: transparent; padding: 8px 0;
  border-radius: 8px; font-size: 14px; color: var(--muted); cursor: pointer;
}
.seg-btn.active { background: var(--card); color: var(--primary); font-weight: 600; box-shadow: 0 1px 3px rgba(0,0,0,.12); }
.hint-tip { font-size: 12px; color: var(--muted); margin: -6px 0 14px 2px; }
.fb-hint { font-size: 12px; color: var(--muted); margin-top: 6px; }

.subject-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 12px;
}
.subject-card {
  background: var(--card);
  border: 0;
  border-radius: var(--radius);
  padding: 18px 14px;
  text-align: left;
  cursor: pointer;
  box-shadow: 0 1px 4px rgba(30,60,120,.08);
  transition: transform .12s ease, box-shadow .12s ease;
}
.subject-card:active { transform: scale(.97); }
.subject-card .s-name { font-size: 17px; font-weight: 700; color: var(--text); }
.subject-card .s-count { font-size: 12px; color: var(--muted); margin-top: 4px; }
.subject-card.mixed {
  grid-column: 1 / -1;
  background: linear-gradient(135deg, var(--primary), #3f8fd4);
}
.subject-card.mixed .s-name, .subject-card.mixed .s-count { color: #fff; }
.subject-card.disabled { opacity: .45; cursor: not-allowed; }

/* ---------- 考试页 ---------- */
#screen-exam { padding: 0 0 76px; display: flex; flex-direction: column; }
.exam-top {
  display: flex; align-items: center; gap: 10px;
  padding: 12px 14px;
  background: var(--card);
  box-shadow: 0 1px 4px rgba(0,0,0,.06);
  position: sticky; top: 0; z-index: 5;
}
.icon-btn {
  border: 0; background: transparent; font-size: 20px; color: var(--muted);
  width: 34px; height: 34px; border-radius: 8px; cursor: pointer;
}
.icon-btn:active { background: #eef2f7; }
.exam-info { flex: 1; min-width: 0; }
.exam-title-row { display: flex; justify-content: space-between; font-size: 13px; margin-bottom: 6px; }
.exam-subject { color: var(--primary-dark); font-weight: 700; }
.exam-progress-text { color: var(--muted); }
.progress-bar { height: 6px; background: #e2e8f0; border-radius: 3px; overflow: hidden; }
.progress-fill { height: 100%; width: 0; background: var(--primary); border-radius: 3px; transition: width .25s ease; }
.exam-score { font-size: 14px; font-weight: 700; white-space: nowrap; }
.exam-score .ok { color: var(--ok); }
.exam-score .ng { color: var(--ng); }
.exam-score .sep { color: var(--muted); margin: 0 2px; }

.exam-body { flex: 1; padding: 14px; }
.q-card {
  background: var(--card); border-radius: var(--radius);
  padding: 16px; box-shadow: 0 1px 4px rgba(30,60,120,.08);
}
.q-index { font-size: 12px; color: var(--muted); margin-bottom: 6px; }
.q-text { font-size: 17px; line-height: 1.6; word-break: break-word; }

.q-options { margin-top: 14px; display: flex; flex-direction: column; gap: 10px; }
.opt-btn {
  display: flex; align-items: flex-start; gap: 10px;
  background: var(--card); border: 1.5px solid #dfe6ef; border-radius: 12px;
  padding: 12px 14px; font-size: 15px; text-align: left; cursor: pointer;
  transition: border-color .12s ease, background .12s ease;
  line-height: 1.5;
}
.opt-btn .opt-letter {
  flex: none; width: 24px; height: 24px; border-radius: 50%;
  background: #eef2f7; color: var(--muted); font-size: 13px; font-weight: 700;
  display: flex; align-items: center; justify-content: center; margin-top: 1px;
}
.opt-btn:not(.locked):active { border-color: var(--primary); background: #f0f6fd; }
.opt-btn.locked { cursor: default; }
.opt-btn.correct { border-color: var(--ok); background: var(--ok-bg); }
.opt-btn.correct .opt-letter { background: var(--ok); color: #fff; }
.opt-btn.wrong { border-color: var(--ng); background: var(--ng-bg); }
.opt-btn.wrong .opt-letter { background: var(--ng); color: #fff; }
.opt-btn.dim { opacity: .55; }

/* ---------- 答题反馈 ---------- */
.feedback {
  margin-top: 14px; border-radius: var(--radius); padding: 14px 16px;
  animation: pop .18s ease;
}
@keyframes pop { from { opacity: 0; transform: translateY(8px); } to { opacity: 1; transform: none; } }
.feedback.ok { background: var(--ok-bg); border: 1px solid #bfe8cd; }
.feedback.ng { background: var(--ng-bg); border: 1px solid #f3c6c6; }
.fb-head { font-size: 16px; font-weight: 800; }
.feedback.ok .fb-head { color: var(--ok); }
.feedback.ng .fb-head { color: var(--ng); }
.fb-answer { font-size: 14px; margin-top: 6px; }
.fb-explain { font-size: 13.5px; color: var(--muted); margin-top: 8px; border-top: 1px dashed #d8d8d8; padding-top: 8px; }

.exam-foot { padding: 0 14px 14px; display: flex; gap: 10px; }
.exam-foot .primary-btn, .exam-foot .ghost-btn { width: auto; flex: 1; }
.exam-foot .ghost-btn:disabled { opacity: .45; cursor: default; }

/* ---------- 通用按钮 ---------- */
.primary-btn {
  width: 100%; border: 0; border-radius: 12px; padding: 14px;
  background: var(--primary); color: #fff; font-size: 17px; font-weight: 700; cursor: pointer;
  box-shadow: 0 2px 8px rgba(43,108,176,.35);
}
.primary-btn:active { background: var(--primary-dark); }
.ghost-btn {
  width: 100%; border: 1.5px solid #cfd9e6; border-radius: 12px; padding: 13px;
  background: var(--card); color: var(--muted); font-size: 15px; cursor: pointer;
}
.ghost-btn.small { width: auto; padding: 6px 12px; font-size: 13px; }

/* ---------- 成绩单 / 统计 ---------- */
.result-top {
  display: flex; align-items: center; justify-content: space-between;
  padding: 6px 0 12px;
}
.result-top h2 { font-size: 19px; color: var(--primary-dark); }
.score-card {
  background: var(--card); border-radius: var(--radius); padding: 22px 16px;
  text-align: center; box-shadow: 0 1px 4px rgba(30,60,120,.08);
}
.big-score { font-size: 52px; font-weight: 800; line-height: 1.1; }
.big-score.pass { color: var(--ok); }
.big-score.fail { color: var(--ng); }
.score-badge {
  display: inline-block; margin-top: 8px; padding: 4px 14px; border-radius: 999px;
  font-size: 14px; font-weight: 700;
}
.score-badge.pass { background: var(--ok-bg); color: var(--ok); }
.score-badge.fail { background: var(--ng-bg); color: var(--ng); }
.score-meta { margin-top: 12px; color: var(--muted); font-size: 14px; display: flex; justify-content: center; gap: 16px; flex-wrap: wrap; }

.sheet-title { font-size: 15px; font-weight: 700; margin: 20px 0 10px; color: var(--text); }
.answer-sheet { display: flex; flex-direction: column; gap: 10px; }
.sheet-item {
  background: var(--card); border-radius: 12px; padding: 12px 14px;
  border-left: 4px solid var(--ok);
  box-shadow: 0 1px 3px rgba(30,60,120,.06);
}
.sheet-item.ng { border-left-color: var(--ng); }
.sheet-item .si-q { font-size: 14.5px; }
.sheet-item .si-a { font-size: 13px; margin-top: 6px; color: var(--muted); }
.sheet-item .si-a .you { font-weight: 700; }
.sheet-item.ng .si-a .you { color: var(--ng); }
.sheet-item.ok .si-a .you { color: var(--ok); }
.sheet-item .si-e { font-size: 12.5px; color: var(--muted); margin-top: 4px; }

.result-actions { display: flex; flex-direction: column; gap: 10px; margin: 22px 0 10px; }

.stats-summary {
  background: var(--card); border-radius: var(--radius); padding: 16px;
  display: flex; justify-content: space-around; text-align: center;
  box-shadow: 0 1px 4px rgba(30,60,120,.08);
}
.stats-summary .num { font-size: 24px; font-weight: 800; color: var(--primary); }
.stats-summary .lbl { font-size: 12px; color: var(--muted); margin-top: 2px; }

.stats-subjects { display: flex; flex-direction: column; gap: 8px; }
.sub-row {
  background: var(--card); border-radius: 10px; padding: 10px 14px;
  display: flex; align-items: center; gap: 10px; font-size: 14px;
  box-shadow: 0 1px 3px rgba(30,60,120,.05);
}
.sub-row .name { width: 76px; font-weight: 700; }
.sub-row .bar { flex: 1; height: 8px; background: #e2e8f0; border-radius: 4px; overflow: hidden; }
.sub-row .bar > i { display: block; height: 100%; background: var(--primary); border-radius: 4px; }
.sub-row .val { width: 108px; text-align: right; color: var(--muted); font-size: 13px; }

.stats-records { display: flex; flex-direction: column; gap: 8px; }
.rec-row {
  background: var(--card); border-radius: 10px; padding: 10px 14px;
  display: flex; align-items: center; justify-content: space-between; gap: 8px;
  font-size: 13.5px; box-shadow: 0 1px 3px rgba(30,60,120,.05);
}
.rec-row .r-date { color: var(--muted); }
.rec-row .r-sub { font-weight: 700; }
.rec-row .r-score { font-weight: 800; }
.rec-row .r-score.pass { color: var(--ok); }
.rec-row .r-score.fail { color: var(--ng); }
.empty-tip { text-align: center; color: var(--muted); font-size: 14px; padding: 30px 0; }

/* ---------- 底部导航 ---------- */
.tabbar {
  position: fixed; bottom: 0; left: 50%; transform: translateX(-50%);
  width: 100%; max-width: 560px;
  display: flex; background: var(--card);
  border-top: 1px solid #e2e8f0;
  padding-bottom: env(safe-area-inset-bottom);
  z-index: 10;
}
.tab {
  flex: 1; border: 0; background: transparent; padding: 13px 0;
  font-size: 15px; color: var(--muted); cursor: pointer; font-weight: 600;
}
.tab.active { color: var(--primary); }