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

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Microsoft YaHei", sans-serif;
  line-height: 1.8;
  color: #2c3e50;
  background: linear-gradient(135deg, #1a365d 0%, #2c5282 100%);
  min-height: 100vh;
}

.container { max-width: 1200px; margin: 0 auto; padding: 0 20px; }

header {
  background: rgba(255, 255, 255, 0.95);
  backdrop-filter: blur(10px);
  box-shadow: 0 2px 10px rgba(0,0,0,0.1);
  padding: 15px 0;
  position: sticky;
  top: 0;
  z-index: 100;
}

header .container { display: flex; justify-content: space-between; align-items: center; }
header h1 { font-size: 24px; color: #1a365d; font-weight: 700; font-family: Georgia, "Times New Roman", serif; }
header h1 a { color: #1a365d; text-decoration: none; }
header nav { display: flex; gap: 20px; align-items: center; }
header nav a { color: #1a365d; text-decoration: none; font-weight: 500; transition: color 0.3s; }
header nav a:hover { color: #d4af37; }
header nav span { color: #666; font-size: 14px; }

/* 主页样式 */
.hero {
  text-align: center;
  padding: 80px 20px;
  background: white;
  border-radius: 20px;
  margin: 40px auto;
  max-width: 900px;
  box-shadow: 0 10px 40px rgba(0,0,0,0.1);
}

.hero h2 {
  font-size: 42px;
  margin-bottom: 15px;
  background: linear-gradient(135deg, #1a365d 0%, #d4af37 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  font-family: Georgia, "Times New Roman", serif;
}

.subtitle { font-size: 20px; color: #666; margin-bottom: 30px; }

.price {
  font-size: 48px;
  color: #e74c3c;
  font-weight: 700;
  margin: 30px 0;
  text-shadow: 2px 2px 4px rgba(0,0,0,0.1);
}

/* 按钮样式 */
.btn-primary {
  display: inline-block;
  background: linear-gradient(135deg, #1a365d 0%, #2c5282 100%);
  color: white;
  padding: 16px 48px;
  text-decoration: none;
  border-radius: 8px;
  font-size: 18px;
  font-weight: 600;
  box-shadow: 0 4px 15px rgba(26, 54, 93, 0.4);
  transition: all 0.3s;
  border: none;
  cursor: pointer;
}

.btn-primary:hover {
  transform: translateY(-2px);
  box-shadow: 0 6px 20px rgba(26, 54, 93, 0.6);
  background: linear-gradient(135deg, #2c5282 0%, #1a365d 100%);
}

.btn-secondary {
  background: linear-gradient(135deg, #3498db 0%, #2980b9 100%);
  color: white;
  padding: 12px 32px;
  border: none;
  border-radius: 50px;
  cursor: pointer;
  font-size: 16px;
  font-weight: 600;
  box-shadow: 0 4px 15px rgba(52, 152, 219, 0.3);
  transition: all 0.3s;
}

.btn-secondary:hover {
  transform: translateY(-2px);
  box-shadow: 0 6px 20px rgba(52, 152, 219, 0.5);
}

/* 讲师卡片 */
.instructor {
  margin: 40px auto;
  max-width: 900px;
  background: white;
  padding: 40px;
  border-radius: 20px;
  box-shadow: 0 10px 40px rgba(0,0,0,0.1);
}

.instructor h3 { font-size: 28px; margin-bottom: 25px; color: #1a365d; font-family: Georgia, "Times New Roman", serif; }

.instructor-card {
  display: flex;
  gap: 30px;
  align-items: center;
  background: linear-gradient(135deg, #f5f7fa 0%, #c3cfe2 100%);
  padding: 30px;
  border-radius: 15px;
}

.instructor-card img {
  width: 150px;
  height: 150px;
  border-radius: 50%;
  object-fit: cover;
  border: 5px solid white;
  box-shadow: 0 4px 15px rgba(0,0,0,0.2);
}

.instructor-info h4 { font-size: 24px; margin-bottom: 10px; color: #333; }
.instructor-info p { color: #666; margin: 5px 0; }

/* 课程目录 */
.catalog {
  margin: 40px auto;
  max-width: 900px;
  background: white;
  padding: 40px;
  border-radius: 20px;
  box-shadow: 0 10px 40px rgba(0,0,0,0.1);
}

.catalog h3 { font-size: 28px; margin-bottom: 25px; color: #1a365d; font-family: Georgia, "Times New Roman", serif; }

details {
  margin: 15px 0;
  border: 2px solid #e0e0e0;
  border-radius: 10px;
  overflow: hidden;
  transition: all 0.3s;
}

details:hover { border-color: #1a365d; }

summary {
  padding: 18px 20px;
  cursor: pointer;
  background: linear-gradient(135deg, #f5f7fa 0%, #c3cfe2 100%);
  font-weight: 600;
  color: #333;
  transition: all 0.3s;
}

summary:hover { background: linear-gradient(135deg, #1a365d 0%, #2c5282 100%); color: white; }

details[open] summary { background: linear-gradient(135deg, #1a365d 0%, #2c5282 100%); color: white; }

details ul { padding: 20px 40px; background: #fafafa; }
details li { margin: 10px 0; color: #666; }

/* 登录页面 */
.login-container {
  max-width: 450px;
  margin: 100px auto;
  text-align: center;
  padding: 50px 40px;
  background: white;
  border-radius: 20px;
  box-shadow: 0 10px 40px rgba(0,0,0,0.15);
}

.login-container h1 {
  margin-bottom: 40px;
  background: linear-gradient(135deg, #1a365d 0%, #2c5282 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

#qrcode { min-height: 220px; display: flex; align-items: center; justify-content: center; }
#qrcode img { width: 200px; height: 200px; border-radius: 10px; box-shadow: 0 4px 15px rgba(0,0,0,0.1); }

.tip { margin-top: 25px; color: #999; font-size: 14px; }

.error {
  color: #e74c3c;
  background: #fee;
  padding: 15px;
  border-radius: 10px;
  border: 2px solid #e74c3c;
  font-weight: 500;
}

/* 课程详情页 */
.course-detail {
  max-width: 900px;
  margin: 40px auto;
  padding: 50px;
  background: white;
  border-radius: 20px;
  box-shadow: 0 10px 40px rgba(0,0,0,0.1);
}

.course-detail h2 {
  font-size: 36px;
  margin-bottom: 20px;
  background: linear-gradient(135deg, #1a365d 0%, #d4af37 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  font-family: Georgia, "Times New Roman", serif;
}

.course-desc { color: #666; margin-bottom: 35px; line-height: 1.8; font-size: 16px; }

.price-box { margin: 35px 0; text-align: center; }
.price-box .price { font-size: 48px; color: #e74c3c; font-weight: 700; }

.notice {
  text-align: center;
  padding: 25px;
  background: linear-gradient(135deg, #fff3cd 0%, #ffe8a1 100%);
  border-radius: 15px;
  border: 2px solid #ffc107;
  font-weight: 500;
}

.notice a { color: #e74c3c; text-decoration: none; font-weight: 600; }

.purchase-options {
  display: flex;
  gap: 40px;
  align-items: center;
  margin-top: 50px;
}

.option {
  flex: 1;
  padding: 30px;
  background: linear-gradient(135deg, #f5f7fa 0%, #c3cfe2 100%);
  border-radius: 15px;
  box-shadow: 0 4px 15px rgba(0,0,0,0.1);
}

.option h3 { font-size: 22px; margin-bottom: 20px; color: #1a365d; }

.option input[type="text"] {
  width: 100%;
  padding: 14px;
  border: 2px solid #ddd;
  border-radius: 10px;
  margin-bottom: 15px;
  font-size: 16px;
  transition: border-color 0.3s;
}

.option input[type="text"]:focus {
  outline: none;
  border-color: #1a365d;
}

.divider { font-size: 24px; color: #999; font-weight: 600; }

/* 视频学习页 */
.learn-container {
  display: flex;
  gap: 25px;
  padding: 25px;
  max-width: 1400px;
  margin: 0 auto;
}

.lesson-list {
  width: 320px;
  background: white;
  padding: 25px;
  border-radius: 15px;
  max-height: 85vh;
  overflow-y: auto;
  box-shadow: 0 4px 15px rgba(0,0,0,0.1);
}

.lesson-list h3 { margin-bottom: 20px; color: #1a365d; font-size: 20px; }
.lesson-list ul { list-style: none; }
.lesson-list li { margin: 10px 0; }

.lesson-list a {
  text-decoration: none;
  color: #333;
  display: block;
  padding: 12px 15px;
  border-radius: 10px;
  transition: all 0.3s;
  font-size: 14px;
}

.lesson-list a:hover { background: linear-gradient(135deg, #f5f7fa 0%, #c3cfe2 100%); }

.lesson-list li.active a {
  background: linear-gradient(135deg, #1a365d 0%, #2c5282 100%);
  color: white;
  font-weight: 600;
  box-shadow: 0 4px 10px rgba(102, 126, 234, 0.3);
}

.video-area {
  flex: 1;
  background: white;
  padding: 30px;
  border-radius: 15px;
  box-shadow: 0 4px 15px rgba(0,0,0,0.1);
}

.video-area h2 { margin-bottom: 25px; color: #1a365d; font-size: 24px; }
.video-area video { border-radius: 12px; box-shadow: 0 4px 20px rgba(0,0,0,0.15); width: 100%; }

/* 个人中心 */
.my-courses {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
  gap: 25px;
  margin-top: 35px;
}

.course-card {
  background: white;
  padding: 30px;
  border-radius: 15px;
  box-shadow: 0 4px 15px rgba(0,0,0,0.1);
  transition: all 0.3s;
}

.course-card:hover {
  transform: translateY(-5px);
  box-shadow: 0 8px 25px rgba(0,0,0,0.15);
}

.course-card h3 { margin-bottom: 15px; color: #1a365d; font-size: 20px; }
.course-card p { color: #666; margin-bottom: 20px; line-height: 1.6; }

.empty {
  text-align: center;
  padding: 80px 20px;
  color: #999;
  background: white;
  border-radius: 15px;
  margin: 40px auto;
  max-width: 600px;
  box-shadow: 0 4px 15px rgba(0,0,0,0.1);
}

/* 管理后台 */
.admin-section {
  margin: 35px 0;
  padding: 30px;
  background: white;
  border-radius: 15px;
  box-shadow: 0 4px 15px rgba(0,0,0,0.1);
}

.admin-section h2 { margin-bottom: 20px; color: #1a365d; font-size: 24px; }

.admin-section form {
  display: flex;
  gap: 20px;
  align-items: center;
  flex-wrap: wrap;
}

.admin-section label {
  display: flex;
  gap: 10px;
  align-items: center;
  font-weight: 500;
}

.admin-section input {
  padding: 10px 15px;
  border: 2px solid #ddd;
  border-radius: 8px;
  font-size: 14px;
  transition: border-color 0.3s;
}

.admin-section input:focus {
  outline: none;
  border-color: #1a365d;
}

/* 表格样式 */
table {
  width: 100%;
  border-collapse: collapse;
  margin-top: 20px;
  background: white;
  border-radius: 10px;
  overflow: hidden;
  box-shadow: 0 2px 10px rgba(0,0,0,0.05);
}

table th, table td {
  padding: 15px;
  text-align: left;
  border-bottom: 1px solid #f0f0f0;
}

table th {
  background: linear-gradient(135deg, #1a365d 0%, #2c5282 100%);
  color: white;
  font-weight: 600;
  text-transform: uppercase;
  font-size: 13px;
  letter-spacing: 0.5px;
}

table tr:hover { background: #f8f9fa; }

/* 响应式设计 */
@media (max-width: 768px) {
  .hero { padding: 40px 20px; }
  .hero h2 { font-size: 28px; }
  .price { font-size: 36px; }

  .instructor-card { flex-direction: column; text-align: center; }

  .purchase-options { flex-direction: column; gap: 20px; }

  .learn-container { flex-direction: column; }
  .lesson-list { width: 100%; max-height: 300px; }

  .my-courses { grid-template-columns: 1fr; }

  header nav { flex-direction: column; gap: 10px; }
}