/* Reset and base styles */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    line-height: 1.6;
    color: #333;
    background-color: #f8f9fa;
}

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

/* Header and Navigation */
header {
    background-color: #fff;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.1);
    position: sticky;
    top: 0;
    z-index: 100;
}

/* === 导航栏样式 === */
.navbar {
  background: white;
  box-shadow: 0 4px 12px rgba(0,0,0,0.1);
  position: sticky;
  top: 0;
  z-index: 1000;
}

.nav-container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 10px 20px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  position: relative;
}

/* logo 靠左 */
.nav-brand {
  /* 移除绝对定位，使其自然排列在左侧 */
}

.nav-brand img {
  height: 50px;
}

/* 导航菜单 */
.nav-menu {
  list-style: none;
  display: flex;
  gap: 40px;
}

.nav-link {
  text-decoration: none;
  color: #333;
  font-weight: 500;
  transition: color 0.3s ease;
}

.nav-link:hover,
.nav-link.active {
  color: #667eea;
}

/* 移动端三杠按钮 */
.nav-toggle {
  display: none;
  font-size: 28px;
  cursor: pointer;
  position: absolute;
  right: 20px;
  top: 14px;
}

/* === 响应式样式 === */
@media (max-width: 768px) {
  .nav-container {
    justify-content: center;
  }

  .nav-brand {
    position: relative;
    left: 0;
    transform: none;
  }

  .nav-brand img {
    height: 45px;
  }

  .nav-toggle {
    display: block;
  }

  .nav-menu {
    display: none;
    position: absolute;
    top: 70px;
    right: 0;
    background: white;
    flex-direction: column;
    width: 200px;
    border-radius: 10px;
    box-shadow: 0 4px 12px rgba(0,0,0,0.1);
    padding: 15px 0;
  }

  .nav-menu.show {
    display: flex;
  }

  .nav-item {
    text-align: center;
    margin: 10px 0;
  }
}

/* Main content sections */
main {
    min-height: calc(100vh - 120px);
}

section {
    padding: 60px 0;
}

section:nth-child(even) {
    background-color: #fff;
}

h1, h2, h3, h4 {
    margin-bottom: 20px;
    color: #2c3e50;
}

h1 {
    font-size: 2.5rem;
}

h2 {
    font-size: 2rem;
    text-align: center;
    position: relative;
    padding-bottom: 15px;
}

h2:after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 50%;
    transform: translateX(-50%);
    width: 80px;
    height: 3px;
    background-color: #3498db;
}

h3 {
    font-size: 1.5rem;
    color: #3498db;
}

p {
    margin-bottom: 15px;
    font-size: 1.1rem;
}

/* Hero sections */
.hero, .library-hero, .groups-hero, .payments-hero, .download-hero {
    background: linear-gradient(135deg, #3498db, #2c3e50);
    color: white;
    text-align: center;
    padding: 80px 0;
}

.hero h1, .library-hero h1, .groups-hero h1, .payments-hero h1, .download-hero h1 {
    font-size: 3rem;
    margin-bottom: 20px;
}

.hero p, .library-hero p, .groups-hero p, .payments-hero p, .download-hero p {
    font-size: 1.3rem;
    max-width: 700px;
    margin: 0 auto;
}

/* About teacher section */
.teacher-info {
    display: flex;
    align-items: center;
    gap: 40px;
    margin-top: 40px;
}

.teacher-photo {
    width: 300px;
    height: 300px;
    border-radius: 50%;
    object-fit: cover;
    border: 5px solid #3498db;
}

.teacher-description {
    flex: 1;
}

/* Courses section */
.course-details {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 30px;
    margin-top: 40px;
}

.course-card {
    background-color: #fff;
    border-radius: 10px;
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.1);
    padding: 30px;
    transition: transform 0.3s;
}

.course-card:hover {
    transform: translateY(-10px);
}

.course-card h3 {
    text-align: center;
    margin-bottom: 20px;
}

.course-card ul {
    list-style-type: none;
    padding-left: 0;
}

.course-card li {
    padding: 10px 0;
    border-bottom: 1px solid #eee;
    position: relative;
    padding-left: 25px;
}

.course-card li:before {
    content: '✓';
    color: #3498db;
    position: absolute;
    left: 0;
    font-weight: bold;
}

/* Pricing section */
.pricing-table {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 30px;
    margin: 50px 0;
}

.pricing-plan {
    background-color: #fff;
    border-radius: 10px;
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.1);
    padding: 40px 30px;
    text-align: center;
    position: relative;
    transition: transform 0.3s;
}

.pricing-plan:hover {
    transform: scale(1.05);
}

.pricing-plan.popular {
    border: 3px solid #3498db;
    transform: scale(1.05);
}

.popular-tag {
    position: absolute;
    top: -15px;
    right: 20px;
    background-color: #3498db;
    color: white;
    padding: 5px 15px;
    border-radius: 20px;
    font-weight: bold;
    font-size: 0.9rem;
}

.price {
    font-size: 2.5rem;
    font-weight: bold;
    color: #3498db;
    margin: 20px 0;
}

.pricing-plan ul {
    list-style: none;
    padding: 0;
    margin: 30px 0;
}

.pricing-plan li {
    padding: 10px 0;
    border-bottom: 1px solid #eee;
}

.payment-methods ul {
    list-style: none;
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: 20px;
    padding: 0;
}

.payment-methods li {
    background-color: #3498db;
    color: white;
    padding: 10px 20px;
    border-radius: 30px;
    font-weight: 500;
}

/* Video showcase */
.video-gallery {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 30px;
    margin-top: 40px;
}

.video-item {
    background-color: #fff;
    border-radius: 10px;
    overflow: hidden;
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.1);
}

.video-item p {
    padding: 15px;
    text-align: center;
    font-weight: 500;
}

/* Library page styles */
.category-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 30px;
    margin-top: 40px;
}

.category-card {
    background-color: #fff;
    border-radius: 10px;
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.1);
    padding: 30px;
    transition: transform 0.3s;
}

.category-card:hover {
    transform: translateY(-10px);
}

.resource-list {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 30px;
    margin-top: 40px;
}

.resource-item {
    background-color: #fff;
    border-radius: 10px;
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.1);
    padding: 30px;
}

/* Groups page styles */
.benefits-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 30px;
    margin-top: 40px;
}

.benefit-card {
    background-color: #fff;
    border-radius: 10px;
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.1);
    padding: 30px;
    text-align: center;
}

.group-list {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 30px;
    margin-top: 40px;
}

.group-item {
    background-color: #fff;
    border-radius: 10px;
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.1);
    padding: 30px;
}

.group-item strong {
    color: #3498db;
}

/* Payments page styles */
.payment-options {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 30px;
    margin-top: 40px;
}

.payment-option {
    background-color: #fff;
    border-radius: 10px;
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.1);
    padding: 30px;
    text-align: center;
}

.payment-icon {
    width: 80px;
    height: auto;
    margin-top: 20px;
}

.payment-details {
    background-color: #fff;
    border-radius: 10px;
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.1);
    padding: 40px;
    max-width: 600px;
    margin: 40px auto;
}

.form-group {
    margin-bottom: 20px;
}

.form-row {
    display: flex;
    gap: 20px;
}

label {
    display: block;
    margin-bottom: 5px;
    font-weight: 500;
}

input, select {
    width: 100%;
    padding: 12px;
    border: 1px solid #ddd;
    border-radius: 5px;
    font-size: 1rem;
}

.submit-btn {
    width: 100%;
    margin-top: 20px;
    padding: 15px;
    font-size: 1.1rem;
}

.security-icons {
    display: flex;
    justify-content: center;
    gap: 30px;
    margin-top: 20px;
}

.security-icon {
    width: 100px;
    height: auto;
}

/* Download page styles */
.client-features {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 30px;
    margin-top: 40px;
}

.feature {
    text-align: center;
    padding: 20px;
}

.downloads {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 30px;
    margin-top: 40px;
}

.download-card {
    background-color: #fff;
    border-radius: 10px;
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.1);
    padding: 30px;
    text-align: center;
}

.version {
    color: #7f8c8d;
    font-size: 0.9rem;
    margin-top: 10px;
}

.steps {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 30px;
    margin-top: 40px;
}

.step {
    display: flex;
    gap: 20px;
}

.step-number {
    background-color: #3498db;
    color: white;
    width: 40px;
    height: 40px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    flex-shrink: 0;
    font-weight: bold;
    font-size: 1.2rem;
}

/* Buttons */
.btn {
    display: inline-block;
    background-color: #3498db;
    color: white;
    padding: 12px 30px;
    border-radius: 30px;
    text-decoration: none;
    font-weight: 500;
    transition: all 0.3s;
    border: none;
    cursor: pointer;
    font-size: 1rem;
}

.btn:hover {
    background-color: #2980b9;
    transform: translateY(-3px);
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.1);
}

.download-btn {
    background-color: #27ae60;
}

.download-btn:hover {
    background-color: #219653;
}

/* Footer */
footer {
    background-color: #2c3e50;
    color: white;
    text-align: center;
    padding: 20px 0;
}

/* Responsive design */
@media (max-width: 768px) {
    .navbar {
        flex-direction: column;
        padding: 15px 0;
    }
    
    .nav-menu {
        margin-top: 20px;
        flex-wrap: wrap;
        justify-content: center;
    }
    
    .nav-item {
        margin: 5px 10px;
    }
    
    .teacher-info {
        flex-direction: column;
        text-align: center;
    }
    
    .teacher-photo {
        width: 200px;
        height: 200px;
    }
    
    .form-row {
        flex-direction: column;
        gap: 0;
    }
    
    h1 {
        font-size: 2rem;
    }
    
    h2 {
        font-size: 1.5rem;
    }
    
    .hero h1, .library-hero h1, .groups-hero h1, .payments-hero h1, .download-hero h1 {
        font-size: 2rem;
    }
    
    .hero p, .library-hero p, .groups-hero p, .payments-hero p, .download-hero p {
        font-size: 1.1rem;
    }
}