:root {
  color-scheme: light;
  --bg: #f6f7f2;
  --ink: #17201c;
  --muted: #69736f;
  --line: #d9ddd1;
  --panel: #ffffff;
  --red: #b4282f;
  --green: #1f7a55;
  --blue: #22577a;
  --gold: #b67b17;
  --soft-red: #fff0f1;
  --soft-green: #eef9f3;
  --shadow: 0 16px 40px rgba(20, 31, 28, 0.08);
  font-family: Inter, "Segoe UI", "Microsoft YaHei", sans-serif;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  min-height: 100vh;
  background: var(--bg);
  color: var(--ink);
}

button, select {
  font: inherit;
}

.topbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
  padding: 24px clamp(18px, 4vw, 48px);
  border-bottom: 1px solid var(--line);
  background: #fff;
}

h1, h2, h3, p {
  margin-top: 0;
}

h1 {
  margin-bottom: 0;
  font-size: clamp(28px, 4vw, 44px);
}

.eyebrow {
  margin-bottom: 6px;
  color: var(--red);
  font-size: 12px;
  font-weight: 800;
  letter-spacing: 0;
  text-transform: uppercase;
}

.status-strip {
  display: grid;
  grid-template-columns: repeat(3, minmax(82px, 1fr));
  gap: 10px;
}

.status-strip div {
  min-width: 82px;
  padding: 10px 14px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #fafbf8;
}

.status-strip strong {
  display: block;
  font-size: 22px;
}

.status-strip span {
  color: var(--muted);
  font-size: 13px;
}

.app-shell {
  display: grid;
  grid-template-columns: 280px minmax(0, 1fr);
  gap: 24px;
  padding: 24px clamp(18px, 4vw, 48px);
}

.sidebar {
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.mode-tabs {
  display: grid;
  gap: 8px;
}

.tab, .primary, .secondary {
  min-height: 42px;
  border: 1px solid var(--line);
  border-radius: 8px;
  cursor: pointer;
  transition: transform 0.15s ease, border-color 0.15s ease, background 0.15s ease;
}

.tab {
  padding: 12px 14px;
  background: #fff;
  color: var(--ink);
  text-align: left;
}

.tab.active {
  border-color: var(--red);
  background: var(--soft-red);
  color: var(--red);
  font-weight: 800;
}

.tab:hover, .primary:hover, .secondary:hover, .option:hover {
  transform: translateY(-1px);
}

.panel, .question-card, .guide-grid section {
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--panel);
  box-shadow: var(--shadow);
}

.panel {
  padding: 18px;
}

.panel h2 {
  margin-bottom: 14px;
  font-size: 18px;
}

.panel p {
  margin-bottom: 0;
  color: var(--muted);
  line-height: 1.6;
}

select {
  width: 100%;
  min-height: 42px;
  padding: 0 12px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #fff;
}

.toggle {
  display: flex;
  align-items: center;
  gap: 10px;
  margin: 14px 0;
  color: var(--muted);
}

.workspace {
  min-width: 0;
}

.workspace-head {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  margin-bottom: 16px;
}

.workspace-head h2 {
  margin-bottom: 0;
  font-size: clamp(24px, 3vw, 34px);
}

.view {
  display: none;
}

.view.active {
  display: block;
}

.question-card {
  padding: clamp(20px, 4vw, 34px);
}

.meta-row {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-bottom: 18px;
}

.pill {
  display: inline-flex;
  align-items: center;
  min-height: 28px;
  padding: 4px 10px;
  border-radius: 999px;
  background: #eef3f6;
  color: var(--blue);
  font-size: 13px;
  font-weight: 700;
}

.question-card h3 {
  font-size: clamp(22px, 3vw, 32px);
  line-height: 1.25;
}

.options {
  display: grid;
  gap: 10px;
  margin: 22px 0;
}

.option {
  display: grid;
  grid-template-columns: 34px 1fr;
  align-items: center;
  gap: 12px;
  width: 100%;
  padding: 14px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #fff;
  text-align: left;
  cursor: pointer;
}

.option .letter {
  display: inline-grid;
  place-items: center;
  width: 34px;
  height: 34px;
  border-radius: 50%;
  background: #edf1ec;
  font-weight: 800;
}

.option.correct {
  border-color: var(--green);
  background: var(--soft-green);
}

.option.selected {
  border-color: var(--blue);
  background: #eef6fa;
}

.option.incorrect {
  border-color: var(--red);
  background: var(--soft-red);
}

.option:disabled {
  cursor: default;
}

.explanation {
  display: none;
  margin-top: 18px;
  padding: 16px;
  border-left: 4px solid var(--gold);
  background: #fff9ec;
  line-height: 1.65;
}

.explanation.visible {
  display: block;
}

.primary {
  padding: 0 18px;
  border-color: var(--red);
  background: var(--red);
  color: #fff;
  font-weight: 800;
}

.secondary {
  padding: 0 14px;
  background: #fff;
  color: var(--ink);
}

.exam-actions {
  display: flex;
  align-items: center;
  gap: 12px;
}

.timer {
  min-width: 76px;
  padding: 9px 12px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #fff;
  color: var(--blue);
  font-weight: 900;
  text-align: center;
}

.exam-nav {
  display: flex;
  align-items: center;
  justify-content: flex-start;
  gap: 10px;
  margin-top: 20px;
}

.empty-state {
  color: var(--muted);
}

.review-list {
  display: grid;
  gap: 12px;
}

.review-item {
  padding: 18px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #fff;
}

.review-item.result-correct {
  border-color: var(--green);
  background: var(--soft-green);
}

.review-item.result-incorrect {
  border-color: var(--red);
  background: var(--soft-red);
}

.review-item h3 {
  margin-bottom: 10px;
  font-size: 18px;
}

.answer-line {
  margin-bottom: 8px;
  line-height: 1.55;
}

.guide-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 16px;
}

.guide-grid section {
  padding: 22px;
}

.guide-grid li {
  margin-bottom: 12px;
  line-height: 1.65;
}

footer {
  padding: 10px clamp(18px, 4vw, 48px) 28px;
  color: var(--muted);
  font-size: 13px;
}

@media (max-width: 860px) {
  .topbar, .workspace-head {
    align-items: stretch;
    flex-direction: column;
  }

  .status-strip, .app-shell, .guide-grid {
    grid-template-columns: 1fr;
  }

  .sidebar {
    order: 2;
  }

  .workspace {
    order: 1;
  }

  .exam-actions {
    justify-content: space-between;
  }
}