:root {
  --bg: #f4f5f7;
  --surface: #ffffff;
  --border: #e1e4e8;
  --text: #24292e;
  --muted: #6a737d;
  --primary: #0366d6;
  --primary-hover: #024ea4;
  --success: #28a745;
  --success-bg: #e6f4ea;
  --danger: #d73a49;
  --danger-bg: #fde7e9;
  --warn-bg: #fff8c5;
  --shadow: 0 1px 3px rgba(27, 31, 35, 0.06);
}

* { box-sizing: border-box; }

body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang TC",
    "Microsoft JhengHei", "Noto Sans CJK TC", sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.55;
}

header {
  background: var(--surface);
  border-bottom: 1px solid var(--border);
  padding: 12px 24px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  flex-wrap: wrap;
}

header h1 { font-size: 1.15rem; margin: 0; }

#topnav { display: flex; gap: 6px; }

main {
  max-width: 960px;
  margin: 0 auto;
  padding: 20px 16px 80px;
}

.view { display: none; }
.view.active { display: block; }

.card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 24px;
  box-shadow: var(--shadow);
  margin-bottom: 16px;
}

h2 { margin-top: 0; }
h3 { margin: 24px 0 8px; font-size: 1.05rem; }
.muted { color: var(--muted); font-size: 0.9rem; }

.status-bar {
  background: var(--warn-bg);
  border-radius: 6px;
  padding: 8px 12px;
  font-size: 0.9rem;
  margin-bottom: 16px;
}
.status-bar.ok { background: var(--success-bg); }

.mode-block {
  border-top: 1px solid var(--border);
  padding-top: 16px;
  margin-top: 16px;
}
.mode-block:first-of-type { border-top: none; padding-top: 0; margin-top: 0; }

.range-row {
  display: flex;
  gap: 16px;
  margin: 8px 0 12px;
  flex-wrap: wrap;
}
.range-row label { font-size: 0.9rem; }
.range-row input {
  margin-left: 6px;
  width: 90px;
  padding: 6px 10px;
  border: 1px solid var(--border);
  border-radius: 4px;
  font: inherit;
}

.chip-row {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
  margin: 8px 0 12px;
}

button {
  font: inherit;
  cursor: pointer;
  border-radius: 6px;
  padding: 8px 16px;
  border: 1px solid var(--border);
  background: var(--surface);
  transition: background 0.12s, border-color 0.12s;
}
button:hover { background: #f0f3f6; }
button:active { transform: translateY(1px); }
button:disabled { opacity: 0.5; cursor: not-allowed; }

button.primary {
  background: var(--primary);
  color: #fff;
  border-color: var(--primary);
}
button.primary:hover { background: var(--primary-hover); border-color: var(--primary-hover); }

button.ghost { background: transparent; }
button.danger { color: var(--danger); border-color: var(--danger); }
button.danger:hover { background: var(--danger-bg); }

.chip {
  padding: 4px 12px;
  font-size: 0.85rem;
  border-radius: 999px;
  background: #f0f3f6;
}
.chip.active {
  background: var(--primary);
  color: #fff;
  border-color: var(--primary);
}

.navbtn { padding: 6px 12px; }
.navbtn.active {
  background: var(--primary);
  color: #fff;
  border-color: var(--primary);
}

.radio {
  display: block;
  margin: 6px 0;
  font-size: 0.95rem;
}

/* ===== Quiz ===== */
.quiz-toolbar {
  display: flex;
  align-items: center;
  gap: 12px;
  margin-bottom: 12px;
}
.quiz-toolbar span { font-size: 0.9rem; color: var(--muted); }
.progress {
  flex: 1;
  height: 6px;
  background: var(--border);
  border-radius: 999px;
  overflow: hidden;
}
#quiz-progress-bar {
  height: 100%;
  background: var(--primary);
  width: 0%;
  transition: width 0.2s;
}

.qno {
  color: var(--muted);
  font-size: 0.85rem;
  margin-bottom: 4px;
}
.qstem {
  font-size: 1.05rem;
  margin-bottom: 12px;
  white-space: pre-wrap;
}
#q-image {
  display: block;
  max-width: 100%;
  border: 1px solid var(--border);
  border-radius: 4px;
  margin: 12px 0;
}

ul.options { list-style: none; padding: 0; margin: 0; }
ul.options li {
  padding: 10px 14px;
  border: 1px solid var(--border);
  border-radius: 6px;
  margin-bottom: 8px;
  cursor: pointer;
  display: flex;
  gap: 10px;
  align-items: flex-start;
  background: var(--surface);
  transition: border-color 0.12s, background 0.12s;
}
ul.options li:hover { border-color: var(--primary); }
ul.options li.selected {
  border-color: var(--primary);
  background: #f0f7ff;
}
ul.options li.correct {
  border-color: var(--success);
  background: var(--success-bg);
}
ul.options li.wrong {
  border-color: var(--danger);
  background: var(--danger-bg);
}
ul.options li.locked { cursor: default; }
ul.options li.locked:hover { border-color: var(--border); }
ul.options li.locked.selected:hover { border-color: var(--primary); }
ul.options li.locked.correct:hover { border-color: var(--success); }
ul.options li.locked.wrong:hover { border-color: var(--danger); }

.opt-letter {
  font-weight: 600;
  min-width: 1.5em;
}

.feedback {
  margin-top: 12px;
  padding: 10px 12px;
  border-radius: 6px;
  font-weight: 600;
}
.feedback.correct { background: var(--success-bg); color: var(--success); }
.feedback.wrong { background: var(--danger-bg); color: var(--danger); }

.hint-box {
  margin-top: 12px;
  padding: 10px 12px;
  border-radius: 6px;
  background: var(--warn-bg);
  font-size: 0.95rem;
}

.quiz-buttons {
  display: flex;
  gap: 8px;
  margin-top: 16px;
  flex-wrap: wrap;
}

/* ===== Result ===== */
.score-board {
  text-align: center;
  margin: 16px 0 28px;
}
.score-main {
  font-size: 2.2rem;
  font-weight: 700;
}
.score-meta { color: var(--muted); font-size: 0.95rem; }

ul.wrong-list { list-style: none; padding: 0; }
ul.wrong-list li {
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 12px;
  margin-bottom: 8px;
}
ul.wrong-list .qbrief { font-weight: 600; }
ul.wrong-list .qans {
  margin-top: 4px;
  font-size: 0.9rem;
  color: var(--muted);
}
ul.wrong-list .qdetail {
  margin-top: 8px;
  padding-top: 8px;
  border-top: 1px dashed var(--border);
  font-size: 0.9rem;
  white-space: pre-wrap;
  display: none;
}
ul.wrong-list li.open .qdetail { display: block; }

/* ===== History ===== */
.hist-toolbar { display: flex; justify-content: flex-end; gap: 8px; margin-bottom: 8px; }
.hist-table { width: 100%; border-collapse: collapse; }
.hist-table th, .hist-table td {
  padding: 8px 10px;
  border-bottom: 1px solid var(--border);
  text-align: left;
  font-size: 0.92rem;
}
.hist-table th { color: var(--muted); font-weight: 500; }