/* ===== 测试教程网 样式表 ===== */
:root {
  --primary: #4f46e5;
  --primary-dark: #3730a3;
  --primary-light: #818cf8;
  --secondary: #0ea5e9;
  --accent: #f59e0b;
  --success: #10b981;
  --danger: #ef4444;
  --warning: #f59e0b;
  --dark: #1e293b;
  --gray: #64748b;
  --light: #f1f5f9;
  --white: #ffffff;
  --bg: #f8fafc;
  --card-bg: #ffffff;
  --border: #e2e8f0;
  --text: #1e293b;
  --text-light: #64748b;
  --radius: 12px;
  --shadow: 0 4px 6px -1px rgba(0,0,0,0.1), 0 2px 4px -2px rgba(0,0,0,0.06);
  --shadow-lg: 0 10px 15px -3px rgba(0,0,0,0.1), 0 4px 6px -4px rgba(0,0,0,0.05);
  --transition: all 0.3s ease;
}

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

html { scroll-behavior: smooth; }

body {
  font-family: 'Segoe UI', system-ui, -apple-system, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.6;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

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

/* ===== 导航栏 ===== */
.navbar {
  position: sticky; top: 0; z-index: 1000;
  background: rgba(255,255,255,0.95);
  backdrop-filter: blur(10px);
  box-shadow: var(--shadow);
  transition: var(--transition);
}
.navbar.scrolled { box-shadow: var(--shadow-lg); }
.nav-container {
  max-width: 1200px; margin: 0 auto;
  display: flex; align-items: center; justify-content: space-between;
  padding: 0 20px; height: 64px;
}
.nav-logo { display: flex; align-items: center; gap: 8px; font-size: 1.3rem; font-weight: 700; color: var(--dark); }
.logo-icon { font-size: 1.5rem; }
.logo-text { background: linear-gradient(135deg, var(--primary), var(--secondary)); -webkit-background-clip: text; -webkit-text-fill-color: transparent; background-clip: text; }
.nav-menu { display: flex; list-style: none; gap: 8px; }
.nav-menu a {
  display: block; padding: 8px 16px; border-radius: 8px;
  font-weight: 500; color: var(--text);
}
.nav-menu a:hover, .nav-menu a.active { background: var(--primary); color: var(--white); }
.nav-toggle { display: none; flex-direction: column; gap: 5px; background: none; border: none; cursor: pointer; padding: 4px; }
.nav-toggle span { width: 24px; height: 3px; background: var(--dark); border-radius: 2px; transition: var(--transition); }

/* ===== 主内容 ===== */
main { flex: 1; max-width: 1200px; margin: 0 auto; padding: 30px 20px; width: 100%; }

/* ===== 英雄区 ===== */
.hero {
  text-align: center; padding: 60px 20px;
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  border-radius: 20px; color: white; margin-bottom: 40px;
  position: relative; overflow: hidden;
}
.hero::before {
  content: ''; position: absolute; top: -50%; left: -50%;
  width: 200%; height: 200%;
  background: radial-gradient(circle, rgba(255,255,255,0.1) 1px, transparent 1px);
  background-size: 30px 30px; animation: drift 20s linear infinite;
}
@keyframes drift { from { transform: translate(0,0); } to { transform: translate(30px,30px); } }
.hero h1 { font-size: 2.8rem; margin-bottom: 16px; position: relative; }
.hero p { font-size: 1.2rem; opacity: 0.9; max-width: 600px; margin: 0 auto 30px; position: relative; }
.hero-buttons { display: flex; gap: 16px; justify-content: center; flex-wrap: wrap; position: relative; }
.btn {
  display: inline-block; padding: 12px 32px; border-radius: var(--radius);
  font-weight: 600; font-size: 1rem; cursor: pointer; border: none; transition: var(--transition);
}
.btn-primary { background: var(--white); color: var(--primary); }
.btn-primary:hover { transform: translateY(-2px); box-shadow: var(--shadow-lg); color: var(--primary); }
.btn-outline { background: transparent; color: white; border: 2px solid white; }
.btn-outline:hover { background: white; color: var(--primary); transform: translateY(-2px); }
.btn-accent { background: var(--accent); color: white; }
.btn-accent:hover { background: #d97706; transform: translateY(-2px); }

/* ===== 统计区 ===== */
.stats { display: grid; grid-template-columns: repeat(auto-fit, minmax(200px, 1fr)); gap: 20px; margin-bottom: 40px; }
.stat-card {
  background: var(--card-bg); border-radius: var(--radius); padding: 24px;
  text-align: center; box-shadow: var(--shadow); transition: var(--transition);
}
.stat-card:hover { transform: translateY(-4px); box-shadow: var(--shadow-lg); }
.stat-card .icon { font-size: 2.5rem; margin-bottom: 8px; }
.stat-card .number { font-size: 2rem; font-weight: 700; color: var(--primary); }
.stat-card .label { color: var(--text-light); font-size: 0.95rem; }

/* ===== 卡片网格 ===== */
.section-title { font-size: 1.8rem; margin-bottom: 24px; display: flex; align-items: center; gap: 10px; }
.section-title .icon { font-size: 2rem; }
.card-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(300px, 1fr)); gap: 24px; }
.card {
  background: var(--card-bg); border-radius: var(--radius); overflow: hidden;
  box-shadow: var(--shadow); transition: var(--transition); cursor: pointer;
}
.card:hover { transform: translateY(-6px); box-shadow: var(--shadow-lg); }
.card-header { padding: 20px; background: linear-gradient(135deg, var(--primary), var(--secondary)); color: white; }
.card-header h3 { font-size: 1.2rem; margin-bottom: 4px; }
.card-header .tag { display: inline-block; background: rgba(255,255,255,0.2); padding: 2px 10px; border-radius: 20px; font-size: 0.8rem; }
.card-body { padding: 20px; }
.card-body p { color: var(--text-light); margin-bottom: 12px; }
.card-footer { padding: 0 20px 20px; display: flex; justify-content: space-between; align-items: center; }
.card-footer .level { font-size: 0.85rem; padding: 4px 12px; border-radius: 20px; font-weight: 600; }
.level-beginner { background: #d1fae5; color: #065f46; }
.level-intermediate { background: #fef3c7; color: #92400e; }
.level-advanced { background: #fee2e2; color: #991b1b; }

/* ===== 教程详情 ===== */
.tutorial-detail { background: var(--card-bg); border-radius: var(--radius); padding: 40px; box-shadow: var(--shadow); }
.tutorial-detail h1 { font-size: 2rem; margin-bottom: 16px; }
.tutorial-meta { display: flex; gap: 16px; margin-bottom: 24px; color: var(--text-light); font-size: 0.9rem; }
.tutorial-content { line-height: 1.8; }
.tutorial-content h2 { font-size: 1.5rem; margin: 28px 0 12px; color: var(--primary-dark); border-left: 4px solid var(--primary); padding-left: 12px; }
.tutorial-content h3 { font-size: 1.2rem; margin: 20px 0 8px; }
.tutorial-content p { margin-bottom: 12px; }
.tutorial-content ul, .tutorial-content ol { margin: 12px 0 12px 24px; }
.tutorial-content li { margin-bottom: 6px; }
.tutorial-content pre {
  background: var(--dark); color: #e2e8f0; padding: 16px; border-radius: 8px;
  overflow-x: auto; margin: 16px 0; font-size: 0.9rem;
}
.tutorial-content code { font-family: 'Fira Code', monospace; }
.tutorial-content blockquote { border-left: 4px solid var(--accent); padding: 12px 20px; background: var(--light); border-radius: 0 8px 8px 0; margin: 16px 0; }

/* ===== Quiz ===== */
.quiz-container { background: var(--card-bg); border-radius: var(--radius); padding: 40px; box-shadow: var(--shadow); max-width: 800px; margin: 0 auto; }
.quiz-header { text-align: center; margin-bottom: 30px; }
.quiz-header h2 { font-size: 1.8rem; margin-bottom: 8px; }
.quiz-progress { height: 8px; background: var(--light); border-radius: 4px; overflow: hidden; margin-bottom: 20px; }
.quiz-progress-bar { height: 100%; background: linear-gradient(90deg, var(--primary), var(--secondary)); transition: width 0.3s ease; border-radius: 4px; }
.quiz-question { font-size: 1.3rem; font-weight: 600; margin-bottom: 20px; }
.quiz-options { display: flex; flex-direction: column; gap: 12px; }
.quiz-option {
  padding: 16px 20px; border: 2px solid var(--border); border-radius: 10px;
  cursor: pointer; transition: var(--transition); font-size: 1rem; background: var(--white);
  display: flex; align-items: center; gap: 12px;
}
.quiz-option:hover { border-color: var(--primary); background: var(--light); }
.quiz-option.selected { border-color: var(--primary); background: #eef2ff; }
.quiz-option.correct { border-color: var(--success); background: #d1fae5; }
.quiz-option.wrong { border-color: var(--danger); background: #fee2e2; }
.quiz-option .option-label { width: 32px; height: 32px; border-radius: 50%; background: var(--light); display: flex; align-items: center; justify-content: center; font-weight: 700; flex-shrink: 0; }
.quiz-option.selected .option-label { background: var(--primary); color: white; }
.quiz-option.correct .option-label { background: var(--success); color: white; }
.quiz-option.wrong .option-label { background: var(--danger); color: white; }
.quiz-actions { display: flex; justify-content: space-between; margin-top: 24px; }
.quiz-result { text-align: center; }
.quiz-result .score { font-size: 3rem; font-weight: 700; margin: 20px 0; }
.quiz-result .score-excellent { color: var(--success); }
.quiz-result .score-good { color: var(--primary); }
.quiz-result .score-fair { color: var(--warning); }
.quiz-result .score-poor { color: var(--danger); }
.quiz-review { text-align: left; margin-top: 30px; }
.quiz-review-item { padding: 16px; border-radius: 8px; margin-bottom: 12px; }
.quiz-review-item.correct { background: #d1fae5; }
.quiz-review-item.wrong { background: #fee2e2; }

/* ===== 关于页 ===== */
.about-page { background: var(--card-bg); border-radius: var(--radius); padding: 40px; box-shadow: var(--shadow); }
.about-page h1 { font-size: 2rem; margin-bottom: 20px; }
.about-page h2 { font-size: 1.4rem; margin: 24px 0 12px; color: var(--primary-dark); }
.about-page p { margin-bottom: 12px; color: var(--text-light); }
.feature-list { display: grid; grid-template-columns: repeat(auto-fit, minmax(250px,1fr)); gap: 20px; margin: 20px 0; }
.feature-item { padding: 20px; background: var(--light); border-radius: var(--radius); text-align: center; }
.feature-item .icon { font-size: 2.5rem; margin-bottom: 8px; }
.feature-item h3 { font-size: 1.1rem; margin-bottom: 6px; }
.feature-item p { font-size: 0.9rem; }

/* ===== 页脚 ===== */
.footer { background: var(--dark); color: var(--light); padding: 40px 0 0; margin-top: auto; }
.footer-container { max-width: 1200px; margin: 0 auto; display: grid; grid-template-columns: repeat(auto-fit, minmax(200px,1fr)); gap: 30px; padding: 0 20px; }
.footer-section h3, .footer-section h4 { margin-bottom: 12px; color: white; }
.footer-section ul { list-style: none; }
.footer-section ul li { margin-bottom: 8px; }
.footer-section a { color: var(--light); }
.footer-section a:hover { color: var(--primary-light); }
.social-links { display: flex; gap: 12px; }
.social-links a { font-size: 1.5rem; }
.footer-bottom { text-align: center; padding: 20px; margin-top: 30px; border-top: 1px solid rgba(255,255,255,0.1); }

/* ===== 返回顶部 ===== */
.back-to-top {
  position: fixed; bottom: 30px; right: 30px; width: 48px; height: 48px;
  border-radius: 50%; background: var(--primary); color: white; border: none;
  font-size: 1.5rem; cursor: pointer; box-shadow: var(--shadow-lg);
  opacity: 0; visibility: hidden; transition: var(--transition); z-index: 999;
}
.back-to-top.visible { opacity: 1; visibility: visible; }
.back-to-top:hover { background: var(--primary-dark); transform: translateY(-4px); }

/* ===== 响应式 ===== */
@media (max-width: 768px) {
  .nav-toggle { display: flex; }
  .nav-menu { display: none; position: absolute; top: 64px; left: 0; right: 0; background: white; flex-direction: column; padding: 16px; box-shadow: var(--shadow-lg); }
  .nav-menu.open { display: flex; }
  .hero h1 { font-size: 2rem; }
  .hero p { font-size: 1rem; }
  .hero-buttons { flex-direction: column; align-items: center; }
  .tutorial-detail, .quiz-container, .about-page { padding: 20px; }
  .card-grid { grid-template-columns: 1fr; }
}