:root {
  --primary: #2b6de8;
  --primary-dark: #1f55c4;
  --primary-light: #e8f0fe;
  --success: #0a9d58;
  --warning: #f29900;
  --danger: #e02020;
  --bg: #f4f6fb;
  --card: #ffffff;
  --text: #1f2733;
  --text-light: #6b7686;
  --border: #e3e8f0;
  --shadow: 0 6px 20px rgba(31, 52, 90, 0.08);
  --radius: 14px;
}

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC",
    "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.7;
  min-height: 100vh;
}

a {
  color: var(--primary);
  text-decoration: none;
}

/* 顶部导航 */
.topbar {
  background: linear-gradient(135deg, #1f55c4 0%, #3a7dff 100%);
  color: #fff;
  padding: 14px 0;
  position: sticky;
  top: 0;
  z-index: 100;
  box-shadow: 0 3px 12px rgba(31, 85, 196, 0.25);
}

.topbar .inner {
  max-width: 1100px;
  margin: 0 auto;
  padding: 0 20px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 10px;
}

.brand {
  display: flex;
  align-items: center;
  gap: 10px;
  font-weight: 700;
  font-size: 18px;
  cursor: pointer;
}

.brand .logo {
  width: 34px;
  height: 34px;
  background: rgba(255, 255, 255, 0.2);
  border-radius: 9px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 18px;
}

.topnav {
  display: flex;
  gap: 8px;
  align-items: center;
  flex-wrap: wrap;
}

.nav-btn {
  background: rgba(255, 255, 255, 0.14);
  color: #fff;
  border: none;
  padding: 8px 16px;
  border-radius: 20px;
  font-size: 14px;
  cursor: pointer;
  transition: 0.2s;
}

.nav-btn:hover,
.nav-btn.active {
  background: #fff;
  color: var(--primary);
}

/* 容器 */
.container {
  max-width: 1100px;
  margin: 0 auto;
  padding: 24px 20px 60px;
}

/* 卡片 */
.card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 24px;
}

.page-title {
  font-size: 26px;
  font-weight: 700;
  margin-bottom: 6px;
}

.page-sub {
  color: var(--text-light);
  margin-bottom: 20px;
}

.section-title {
  font-size: 20px;
  font-weight: 700;
  margin: 26px 0 14px;
  padding-left: 12px;
  border-left: 4px solid var(--primary);
}

/* 首页 */
.hero {
  background: linear-gradient(135deg, #1f55c4, #3a7dff);
  color: #fff;
  border-radius: var(--radius);
  padding: 40px;
  margin-bottom: 28px;
  box-shadow: 0 10px 30px rgba(31, 85, 196, 0.25);
}

.hero h1 {
  font-size: 30px;
  margin-bottom: 12px;
}

.hero p {
  opacity: 0.95;
  max-width: 720px;
}

.hero .badge {
  display: inline-block;
  background: rgba(255, 255, 255, 0.18);
  padding: 5px 14px;
  border-radius: 20px;
  font-size: 13px;
  margin-top: 16px;
}

.stats {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
  gap: 14px;
  margin-bottom: 28px;
}

.stat-card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 18px;
  text-align: center;
  box-shadow: var(--shadow);
}

.stat-card .num {
  font-size: 28px;
  font-weight: 700;
  color: var(--primary);
}

.stat-card .label {
  color: var(--text-light);
  font-size: 13px;
  margin-top: 4px;
}

/* 阶段列表 */
.stage-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 18px;
  margin-top: 10px;
}

.stage-card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 22px;
  box-shadow: var(--shadow);
  display: flex;
  flex-direction: column;
  gap: 10px;
  cursor: pointer;
  transition: 0.2s;
  border-top: 4px solid var(--primary);
}

.stage-card:hover {
  transform: translateY(-3px);
  box-shadow: 0 12px 28px rgba(31, 52, 90, 0.14);
}

.stage-card .level {
  align-self: flex-start;
  background: var(--primary-light);
  color: var(--primary);
  font-size: 12px;
  font-weight: 600;
  padding: 3px 12px;
  border-radius: 12px;
}

.stage-card h3 {
  font-size: 18px;
}

.stage-card p {
  color: var(--text-light);
  font-size: 14px;
  flex: 1;
}

.stage-card .meta {
  font-size: 13px;
  color: var(--text-light);
  display: flex;
  gap: 14px;
  flex-wrap: wrap;
}

/* 章节 */
.chapter-list {
  margin-top: 10px;
}

.chapter-item {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 16px 20px;
  margin-bottom: 12px;
  display: flex;
  align-items: center;
  gap: 16px;
  cursor: pointer;
  transition: 0.2s;
}

.chapter-item:hover {
  border-color: var(--primary);
  box-shadow: var(--shadow);
}

.chapter-item .idx {
  width: 40px;
  height: 40px;
  border-radius: 50%;
  background: var(--primary-light);
  color: var(--primary);
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 700;
  flex-shrink: 0;
}

.chapter-item.done .idx {
  background: var(--success);
  color: #fff;
}

.chapter-item .info {
  flex: 1;
}

.chapter-item .info h4 {
  font-size: 16px;
}

.chapter-item .info .desc {
  font-size: 13px;
  color: var(--text-light);
}

/* 学习内容 */
.article {
  background: var(--card);
  border-radius: var(--radius);
  padding: 28px;
  box-shadow: var(--shadow);
}

.article h2 {
  font-size: 22px;
  margin-bottom: 14px;
}

.article .content {
  margin: 16px 0;
  font-size: 15px;
}

.keypoints {
  margin: 18px 0;
  padding: 16px 20px;
  background: var(--primary-light);
  border-radius: 12px;
}

.keypoints h4 {
  color: var(--primary);
  margin-bottom: 8px;
}

.keypoints .tag {
  display: inline-block;
  background: #fff;
  color: var(--primary);
  padding: 4px 12px;
  border-radius: 16px;
  font-size: 13px;
  margin: 4px 6px 4px 0;
  border: 1px solid var(--primary);
}

.nav-buttons {
  display: flex;
  justify-content: space-between;
  margin-top: 24px;
  gap: 10px;
}

/* 按钮 */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  border: none;
  border-radius: 8px;
  padding: 10px 20px;
  font-size: 14px;
  cursor: pointer;
  transition: 0.2s;
}

.btn-primary {
  background: var(--primary);
  color: #fff;
}

.btn-primary:hover {
  background: var(--primary-dark);
}

.btn-outline {
  background: #fff;
  color: var(--primary);
  border: 1px solid var(--primary);
}

.btn-outline:hover {
  background: var(--primary-light);
}

.btn-success {
  background: var(--success);
  color: #fff;
}

.btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
}

/* 考试 */
.exam-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 16px;
  flex-wrap: wrap;
  gap: 10px;
}

.timer {
  font-size: 18px;
  font-weight: 700;
  color: var(--primary);
  background: var(--primary-light);
  padding: 6px 16px;
  border-radius: 20px;
}

.question {
  margin-bottom: 22px;
  padding: 20px;
  border: 1px solid var(--border);
  border-radius: 12px;
  background: #fafbfd;
}

.question .q-text {
  font-weight: 600;
  margin-bottom: 12px;
}

.question .type-tag {
  font-size: 12px;
  padding: 2px 10px;
  border-radius: 10px;
  background: #eee;
  color: var(--text-light);
  margin-left: 8px;
}

.options {
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.option {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 10px 14px;
  border: 1px solid var(--border);
  border-radius: 8px;
  cursor: pointer;
  transition: 0.15s;
  background: #fff;
}

.option:hover {
  border-color: var(--primary);
}

.option.selected {
  border-color: var(--primary);
  background: var(--primary-light);
}

.option input {
  accent-color: var(--primary);
}

/* 评分结果 */
.result-hero {
  text-align: center;
  padding: 34px;
  border-radius: var(--radius);
  color: #fff;
  margin-bottom: 24px;
}

.result-hero .score {
  font-size: 60px;
  font-weight: 800;
}

.result-hero .grade {
  font-size: 20px;
  margin-top: 6px;
}

.result-hero .detail {
  margin-top: 14px;
  opacity: 0.95;
}

.grade-excellent { background: linear-gradient(135deg, #0a9d58, #2ec77e); }
.grade-good { background: linear-gradient(135deg, #f29900, #ffb93d); }
.grade-pass { background: linear-gradient(135deg, #e02020, #ff5a5a); }

.review-item {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 16px 20px;
  margin-bottom: 12px;
}

.review-item .q {
  font-weight: 600;
}

.review-item .your-answer {
  font-size: 14px;
  margin-top: 6px;
}

.review-item .correct { color: var(--success); }
.review-item .wrong { color: var(--danger); }

.review-item .analysis {
  font-size: 13px;
  color: var(--text-light);
  margin-top: 6px;
  border-top: 1px dashed var(--border);
  padding-top: 6px;
}

/* 学习档案 */
.history-list {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.history-item {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 16px 20px;
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 10px;
}

.history-item .stage {
  font-weight: 600;
}

.history-item .score {
  font-weight: 700;
  color: var(--primary);
  font-size: 18px;
}

.history-item .time {
  font-size: 13px;
  color: var(--text-light);
}

.empty-tip {
  text-align: center;
  color: var(--text-light);
  padding: 40px 0;
}

/* 进度条 */
.progress-wrap {
  background: #eef1f6;
  border-radius: 20px;
  height: 10px;
  overflow: hidden;
  margin: 6px 0;
}

.progress-bar {
  height: 100%;
  background: linear-gradient(90deg, var(--primary), #3a7dff);
  border-radius: 20px;
  transition: width 0.4s;
}

/* 页脚 */
.footer {
  text-align: center;
  color: var(--text-light);
  font-size: 13px;
  padding: 24px;
  border-top: 1px solid var(--border);
  margin-top: 20px;
}

@media (max-width: 640px) {
  .hero { padding: 26px; }
  .hero h1 { font-size: 24px; }
  .container { padding: 16px 14px 40px; }
  .topbar .inner { flex-direction: column; align-items: flex-start; }
}