:root {
  --bg: #f5efe6;
  --panel: #fffaf4;
  --panel-strong: #ffffff;
  --ink: #1f2528;
  --muted: #667075;
  --line: rgba(31, 37, 40, 0.08);
  --accent: #cb5626;
  --accent-soft: #f8decf;
  --green: #14624d;
  --green-soft: #ddefe7;
  --red: #a0372c;
  --red-soft: #f8ded8;
  --shadow: 0 30px 60px rgba(90, 63, 44, 0.12);
  --radius-xl: 28px;
  --radius-lg: 22px;
  --radius-md: 16px;
  --radius-sm: 12px;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  color: var(--ink);
  font-family: "Avenir Next", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
  background:
    radial-gradient(circle at top left, rgba(203, 86, 38, 0.15), transparent 32%),
    radial-gradient(circle at bottom right, rgba(20, 98, 77, 0.11), transparent 28%),
    linear-gradient(180deg, #fbf5ed 0%, #efe7db 100%);
}

button {
  font: inherit;
  cursor: pointer;
}

.hidden {
  display: none !important;
}

.app-shell {
  max-width: 1400px;
  min-height: 100vh;
  margin: 0 auto;
  display: grid;
  grid-template-columns: 280px minmax(0, 1fr);
  gap: 24px;
  padding: 24px;
}

.sidebar,
.content {
  background: rgba(255, 251, 246, 0.72);
  backdrop-filter: blur(12px);
  border: 1px solid rgba(255, 255, 255, 0.7);
  box-shadow: var(--shadow);
}

.sidebar {
  border-radius: 32px;
  padding: 22px;
  display: flex;
  flex-direction: column;
  gap: 22px;
}

.brand-card {
  display: grid;
  grid-template-columns: 68px 1fr;
  gap: 16px;
  align-items: center;
  padding: 18px;
  border-radius: var(--radius-lg);
  background: linear-gradient(180deg, rgba(255,255,255,0.96), rgba(250,241,232,0.96));
  border: 1px solid var(--line);
}

.brand-mark {
  width: 68px;
  height: 68px;
  border-radius: 22px;
  display: grid;
  place-items: center;
  background: linear-gradient(135deg, #e87343, #bc471c);
  color: #fff;
  font-weight: 800;
  font-size: 22px;
}

.eyebrow {
  margin: 0 0 6px;
  color: var(--accent);
  font-size: 12px;
  font-weight: 800;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.brand-card h1,
.hero-card h2,
.section-head h2,
.question-card h3 {
  margin: 0;
}

.nav-list {
  display: grid;
  gap: 10px;
}

.nav-item {
  border: 0;
  border-radius: 18px;
  padding: 14px 16px;
  text-align: left;
  background: transparent;
  color: var(--muted);
}

.nav-item.active {
  background: rgba(203, 86, 38, 0.12);
  color: var(--accent);
  font-weight: 700;
}

.rule-card {
  margin-top: auto;
  padding: 18px;
  border-radius: var(--radius-lg);
  background: linear-gradient(180deg, rgba(255,255,255,0.95), rgba(248,239,228,0.95));
  border: 1px solid var(--line);
}

.rule-card h2 {
  margin: 0 0 12px;
  font-size: 18px;
}

.rule-card ul {
  margin: 0;
  padding-left: 18px;
  color: var(--muted);
  line-height: 1.7;
}

.content {
  border-radius: 32px;
  padding: 24px;
}

.screen {
  display: none;
}

.screen.active {
  display: block;
}

.hero-card,
.question-card,
.stat-card,
.level-card,
.feedback-card,
.wrong-item {
  background: rgba(255, 255, 255, 0.95);
  border: 1px solid var(--line);
  border-radius: var(--radius-lg);
}

.hero-card {
  padding: 24px;
  display: flex;
  justify-content: space-between;
  gap: 18px;
  align-items: flex-start;
}

.hero-card p,
.section-head p,
.stat-card span,
.meta,
.wrong-item p,
.wrong-item span,
.feedback-card p,
#trainingMeta {
  color: var(--muted);
}

.hero-actions,
.section-actions,
.training-actions,
.wrong-actions {
  display: flex;
  gap: 12px;
  flex-wrap: wrap;
}

.primary-btn,
.ghost-btn,
.level-card button,
.wrong-item button {
  border-radius: 14px;
  padding: 12px 16px;
  border: 0;
}

.primary-btn,
.level-card .level-start,
.wrong-item .wrong-start {
  background: var(--accent);
  color: #fff;
}

.ghost-btn {
  background: rgba(31, 37, 40, 0.06);
  color: var(--ink);
}

.stats-grid,
.level-grid,
.wrong-list {
  display: grid;
  gap: 16px;
  margin-top: 20px;
}

.stats-grid {
  grid-template-columns: repeat(4, minmax(0, 1fr));
}

.stat-card {
  padding: 18px;
  display: grid;
  gap: 10px;
}

.stat-card strong {
  font-size: 28px;
}

.section-head {
  display: flex;
  justify-content: space-between;
  gap: 18px;
  align-items: center;
}

.level-grid {
  grid-template-columns: repeat(2, minmax(0, 1fr));
}

.level-card {
  padding: 18px;
  display: grid;
  gap: 14px;
}

.level-card-top {
  display: flex;
  justify-content: space-between;
  gap: 12px;
}

.level-chip {
  align-self: start;
  padding: 6px 10px;
  border-radius: 999px;
  background: var(--accent-soft);
  color: var(--accent);
  font-weight: 700;
  font-size: 13px;
}

.progress-track {
  width: 100%;
  height: 10px;
  border-radius: 999px;
  overflow: hidden;
  background: rgba(31, 37, 40, 0.08);
}

.progress-bar {
  height: 100%;
  border-radius: inherit;
  background: linear-gradient(90deg, #f08c56, #cb5626);
}

.question-card {
  margin-top: 20px;
  padding: 22px;
}

.question-stem {
  margin-top: 18px;
}

.question-stem p,
.option-text p,
.feedback-explanation p {
  margin: 0;
  line-height: 1.7;
}

.question-stem p + p,
.option-text p + p,
.feedback-explanation p + p,
.question-stem .code-block,
.option-text .code-block,
.feedback-explanation .code-block {
  margin-top: 14px;
}

.question-topline {
  display: flex;
  justify-content: space-between;
  gap: 12px;
  color: var(--muted);
  font-size: 14px;
}

.option-list {
  display: grid;
  gap: 12px;
  margin: 20px 0;
}

.option-item {
  display: flex;
  gap: 12px;
  align-items: flex-start;
  padding: 14px 16px;
  border-radius: var(--radius-md);
  border: 1px solid var(--line);
  background: #fffdf9;
}

.option-item input {
  margin-top: 4px;
}

.option-body {
  display: flex;
  gap: 10px;
  flex: 1;
  min-width: 0;
}

.option-key {
  flex: 0 0 auto;
  font-size: 18px;
}

.option-text {
  flex: 1;
  min-width: 0;
}

.code-block {
  border: 1px solid rgba(31, 37, 40, 0.1);
  border-radius: 18px;
  overflow: hidden;
  background: linear-gradient(180deg, #fffdf9, #f4eee6);
}

.code-block-top {
  min-height: 14px;
  padding: 10px 14px 0;
}

.code-lang {
  display: inline-flex;
  align-items: center;
  padding: 4px 8px;
  border-radius: 999px;
  background: rgba(20, 98, 77, 0.1);
  color: var(--green);
  font-size: 12px;
  font-weight: 700;
  letter-spacing: 0.04em;
  text-transform: uppercase;
}

.code-block pre {
  margin: 0;
  padding: 14px 16px 16px;
  overflow-x: auto;
}

.code-block code,
.inline-code {
  font-family: "SFMono-Regular", "JetBrains Mono", "Menlo", "Consolas", monospace;
}

.code-block code {
  display: block;
  font-size: 15px;
  line-height: 1.65;
  white-space: pre;
}

.inline-code {
  padding: 0.12em 0.4em;
  border-radius: 8px;
  background: rgba(31, 37, 40, 0.08);
  font-size: 0.92em;
}

.feedback-card {
  margin-top: 18px;
  padding: 16px 18px;
  display: grid;
  gap: 10px;
}

.feedback-card.correct {
  background: var(--green-soft);
  border-color: rgba(20, 98, 77, 0.18);
}

.feedback-card.wrong {
  background: var(--red-soft);
  border-color: rgba(160, 55, 44, 0.18);
}

.feedback-card strong {
  font-size: 18px;
}

.wrong-list {
  grid-template-columns: 1fr;
}

.wrong-item {
  padding: 18px;
  display: grid;
  gap: 12px;
}

.wrong-item-top {
  display: flex;
  justify-content: space-between;
  gap: 12px;
}

.wrong-item-actions {
  display: flex;
  justify-content: space-between;
  gap: 12px;
  align-items: center;
  flex-wrap: wrap;
}

.empty-state {
  padding: 32px 18px;
  text-align: center;
  color: var(--muted);
  background: rgba(31, 37, 40, 0.03);
  border-radius: var(--radius-lg);
}

@media (max-width: 980px) {
  .app-shell {
    grid-template-columns: 1fr;
  }

  .stats-grid,
  .level-grid {
    grid-template-columns: 1fr;
  }

  .hero-card,
  .section-head {
    flex-direction: column;
    align-items: stretch;
  }
}