/* 组件样式文件 - components.css */

/* 导航栏组件 */
.navbar {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 1000;
  background: rgba(13, 17, 23, 0.95);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--border-color);
  transition: all var(--transition-normal);
}

.navbar.scrolled {
  background: rgba(13, 17, 23, 0.98);
  box-shadow: var(--shadow-md);
}

.nav-container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: var(--spacing-md) var(--spacing-lg);
  max-width: 1200px;
  margin: 0 auto;
}

.nav-brand {
  display: flex;
  align-items: center;
  gap: var(--spacing-sm);
}

.brand-link {
  display: flex;
  align-items: center;
  gap: var(--spacing-sm);
  font-size: var(--text-xl);
  font-weight: 700;
  color: var(--primary-color);
  text-decoration: none;
}

.brand-link i {
  font-size: var(--text-2xl);
}

.nav-menu {
  display: flex;
  align-items: center;
}

.nav-list {
  display: flex;
  list-style: none;
  margin: 0;
  padding: 0;
  gap: var(--spacing-lg);
}

.nav-link {
  padding: var(--spacing-sm) var(--spacing-md);
  color: var(--text-secondary);
  font-weight: 500;
  text-decoration: none;
  border-radius: var(--radius-md);
  transition: all var(--transition-fast);
  position: relative;
}

.nav-link:hover,
.nav-link.active {
  color: var(--primary-color);
  background-color: var(--primary-light);
}

.nav-actions {
  display: flex;
  align-items: center;
  gap: var(--spacing-md);
}

.auth-buttons {
  display: flex;
  gap: var(--spacing-sm);
}

.user-menu {
  position: relative;
}

.user-avatar {
  display: flex;
  align-items: center;
  gap: var(--spacing-sm);
  padding: var(--spacing-sm);
  border-radius: var(--radius-lg);
  cursor: pointer;
  transition: all var(--transition-fast);
}

.user-avatar:hover {
  background-color: var(--bg-secondary);
}

.user-avatar img {
  width: 32px;
  height: 32px;
  border-radius: var(--radius-full);
  object-fit: cover;
}

.user-dropdown {
  position: absolute;
  top: 100%;
  right: 0;
  background: var(--bg-primary);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-lg);
  min-width: 200px;
  padding: var(--spacing-sm);
  opacity: 0;
  visibility: hidden;
  transform: translateY(-10px);
  transition: all var(--transition-fast);
}

.user-dropdown.show {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}

.user-dropdown a {
  display: flex;
  align-items: center;
  gap: var(--spacing-sm);
  padding: var(--spacing-sm) var(--spacing-md);
  color: var(--text-secondary);
  text-decoration: none;
  border-radius: var(--radius-md);
  transition: all var(--transition-fast);
}

.user-dropdown a:hover {
  background-color: var(--bg-secondary);
  color: var(--text-primary);
}

.dropdown-divider {
  height: 1px;
  background-color: var(--border-color);
  margin: var(--spacing-sm) 0;
}

.nav-toggle {
  display: none;
  flex-direction: column;
  gap: 4px;
  padding: var(--spacing-sm);
  background: none;
  border: none;
  cursor: pointer;
}

.nav-toggle span {
  width: 24px;
  height: 2px;
  background-color: var(--text-primary);
  transition: all var(--transition-fast);
}

/* 按钮组件 */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--spacing-sm);
  padding: var(--spacing-sm) var(--spacing-md);
  font-size: var(--text-sm);
  font-weight: 500;
  line-height: 1;
  border: 1px solid transparent;
  border-radius: var(--radius-md);
  cursor: pointer;
  text-decoration: none;
  transition: all var(--transition-fast);
  white-space: nowrap;
  user-select: none;
}

.btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
  pointer-events: none;
}

.btn-primary {
  background-color: var(--primary-color);
  color: var(--text-white);
  border-color: var(--primary-color);
}

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

.btn-outline {
  background-color: transparent;
  color: var(--primary-color);
  border-color: var(--primary-color);
}

.btn-outline:hover {
  background-color: var(--primary-color);
  color: var(--text-white);
}

.btn-secondary {
  background-color: var(--secondary-color);
  color: var(--text-white);
  border-color: var(--secondary-color);
}

.btn-secondary:hover {
  background-color: var(--text-primary);
  border-color: var(--text-primary);
}

.btn-success {
  background-color: var(--success-color);
  color: var(--text-white);
  border-color: var(--success-color);
}

.btn-warning {
  background-color: var(--warning-color);
  color: var(--text-white);
  border-color: var(--warning-color);
}

.btn-error {
  background-color: var(--error-color);
  color: var(--text-white);
  border-color: var(--error-color);
}

.btn-large {
  padding: var(--spacing-md) var(--spacing-xl);
  font-size: var(--text-base);
}

.btn-small {
  padding: var(--spacing-xs) var(--spacing-sm);
  font-size: var(--text-xs);
}

.btn-full {
  width: 100%;
}

.btn-icon {
  padding: var(--spacing-sm);
  width: 40px;
  height: 40px;
}

/* 卡片组件 */
.card {
  background: var(--bg-primary);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-sm);
  overflow: hidden;
  transition: all var(--transition-normal);
}

.card:hover {
  box-shadow: var(--shadow-md);
  transform: translateY(-2px);
}

.card-header {
  padding: var(--spacing-lg);
  border-bottom: 1px solid var(--border-color);
}

.card-body {
  padding: var(--spacing-lg);
}

.card-footer {
  padding: var(--spacing-lg);
  border-top: 1px solid var(--border-color);
  background-color: var(--bg-secondary);
}

.card-image {
  width: 100%;
  height: 200px;
  object-fit: cover;
}

/* 课程卡片 */
.course-card {
  background: var(--bg-primary);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  overflow: hidden;
  transition: all var(--transition-normal);
  cursor: pointer;
}

.course-card:hover {
  box-shadow: var(--shadow-lg);
  transform: translateY(-4px);
}

.course-image {
  position: relative;
  width: 100%;
  height: 200px;
  background: linear-gradient(
    135deg,
    var(--primary-color),
    var(--accent-color)
  );
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--text-white);
  font-size: var(--text-3xl);
}

.course-badge {
  position: absolute;
  top: var(--spacing-sm);
  right: var(--spacing-sm);
  background: rgba(13, 17, 23, 0.9);
  color: var(--text-primary);
  padding: var(--spacing-xs) var(--spacing-sm);
  border-radius: var(--radius-full);
  font-size: var(--text-xs);
  font-weight: 600;
}

.course-content {
  padding: var(--spacing-lg);
}

.course-title {
  font-size: var(--text-lg);
  font-weight: 600;
  margin-bottom: var(--spacing-sm);
  color: var(--text-primary);
}

.course-description {
  color: var(--text-secondary);
  font-size: var(--text-sm);
  margin-bottom: var(--spacing-md);
  line-height: 1.5;
}

.course-meta {
  display: flex;
  align-items: center;
  gap: var(--spacing-md);
  margin-bottom: var(--spacing-md);
  font-size: var(--text-sm);
  color: var(--text-muted);
}

.course-tags {
  display: flex;
  flex-wrap: wrap;
  gap: var(--spacing-xs);
  margin-bottom: var(--spacing-md);
}

.course-tag {
  background: var(--bg-tertiary);
  color: var(--text-secondary);
  padding: var(--spacing-xs) var(--spacing-sm);
  border-radius: var(--radius-full);
  font-size: var(--text-xs);
  font-weight: 500;
}

.course-footer {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding-top: var(--spacing-md);
  border-top: 1px solid var(--border-color);
}

.course-price {
  font-size: var(--text-lg);
  font-weight: 700;
  color: var(--primary-color);
}

.course-rating {
  display: flex;
  align-items: center;
  gap: var(--spacing-xs);
  color: var(--accent-color);
}

/* 模态框组件 */
.modal {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: var(--bg-overlay);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 2000;
  opacity: 0;
  visibility: hidden;
  transition: all var(--transition-normal);
}

.modal.show {
  opacity: 1;
  visibility: visible;
}

.modal-content {
  background: var(--bg-primary);
  border-radius: var(--radius-xl);
  box-shadow: var(--shadow-xl);
  max-width: 500px;
  width: 90%;
  max-height: 90vh;
  overflow-y: auto;
  transform: scale(0.9);
  transition: transform var(--transition-normal);
}

.modal.show .modal-content {
  transform: scale(1);
}

.modal-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: var(--spacing-lg);
  border-bottom: 1px solid var(--border-color);
}

.modal-header h3 {
  margin: 0;
  font-size: var(--text-xl);
  font-weight: 600;
}

.modal-close {
  width: 32px;
  height: 32px;
  border-radius: var(--radius-full);
  background: var(--bg-secondary);
  border: none;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--text-muted);
  transition: all var(--transition-fast);
}

.modal-close:hover {
  background: var(--border-color);
  color: var(--text-primary);
}

.modal-body {
  padding: var(--spacing-lg);
}

.modal-footer {
  padding: var(--spacing-lg);
  border-top: 1px solid var(--border-color);
  text-align: center;
}

/* 表单组件 */
.form-group {
  margin-bottom: var(--spacing-lg);
}

.form-group label {
  display: block;
  margin-bottom: var(--spacing-sm);
  font-weight: 500;
  color: var(--text-primary);
}

.form-group input,
.form-group textarea,
.form-group select {
  width: 100%;
  padding: var(--spacing-sm) var(--spacing-md);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  font-size: var(--text-base);
  background: var(--bg-primary);
  color: var(--text-primary);
  transition: all var(--transition-fast);
}

.form-group input:focus,
.form-group textarea:focus,
.form-group select:focus {
  outline: none;
  border-color: var(--primary-color);
  box-shadow: 0 0 0 3px var(--primary-light);
}

.form-group textarea {
  resize: vertical;
  min-height: 100px;
}

.form-options {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: var(--spacing-lg);
}

.checkbox-label {
  display: flex;
  align-items: center;
  gap: var(--spacing-sm);
  cursor: pointer;
  font-size: var(--text-sm);
}

.checkbox-label input[type="checkbox"] {
  width: auto;
  margin: 0;
}

.checkmark {
  width: 18px;
  height: 18px;
  border: 2px solid var(--border-color);
  border-radius: var(--radius-sm);
  position: relative;
  transition: all var(--transition-fast);
}

.checkbox-label input[type="checkbox"]:checked + .checkmark {
  background-color: var(--primary-color);
  border-color: var(--primary-color);
}

.checkbox-label input[type="checkbox"]:checked + .checkmark::after {
  content: "✓";
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  color: white;
  font-size: 12px;
  font-weight: bold;
}

.forgot-password {
  color: var(--primary-color);
  font-size: var(--text-sm);
  text-decoration: none;
}

.forgot-password:hover {
  text-decoration: underline;
}

/* ===== COURSES SECTION ===== */
.courses {
  padding: 80px 0;
  background: var(--bg-secondary);
}

.section-header {
  text-align: center;
  margin-bottom: 4rem;
  max-width: 800px;
  margin-left: auto;
  margin-right: auto;
}

.section-badge {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  background: var(--primary-light);
  color: var(--primary-color);
  padding: 8px 20px;
  border-radius: 25px;
  font-size: 0.9rem;
  font-weight: 500;
  margin-bottom: 1rem;
}

.section-title {
  font-size: 2.5rem;
  color: var(--text-primary);
  margin-bottom: 1rem;
  font-weight: 700;
}

.section-description {
  font-size: 1.1rem;
  color: var(--text-secondary);
  margin-bottom: 2rem;
  line-height: 1.6;
}

/* 筛选器组件 */
.course-filters {
  display: flex;
  flex-wrap: wrap;
  gap: var(--spacing-sm);
  margin-bottom: var(--spacing-xl);
  justify-content: center;
}

.filter-btn {
  display: flex;
  align-items: center;
  gap: 8px;
  background: var(--card-bg);
  color: var(--text-secondary);
  border: 2px solid var(--border-color);
  padding: 10px 20px;
  border-radius: 25px;
  cursor: pointer;
  font-weight: 500;
  transition: all 0.3s ease;
  text-decoration: none;
}

.filter-btn:hover,
.filter-btn.active {
  background: var(--primary-color);
  color: white;
  border-color: var(--primary-color);
  transform: translateY(-2px);
}

.learning-modules {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(380px, 1fr));
  gap: 2rem;
  max-width: 1400px;
  margin: 0 auto;
}

.module-card {
  background: var(--card-bg);
  border-radius: 20px;
  overflow: hidden;
  box-shadow: var(--shadow-card);
  transition: all 0.3s ease;
  border: 1px solid var(--border-color);
  position: relative;
  display: flex;
  flex-direction: column;
}

.module-card:hover {
  transform: translateY(-8px);
  box-shadow: var(--shadow-hover);
}

.card-header {
  position: relative;
  padding: 2rem 2rem 1rem;
  background: linear-gradient(
    135deg,
    var(--primary-light) 0%,
    var(--secondary-light) 100%
  );
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
}

.module-icon {
  width: 60px;
  height: 60px;
  background: var(--primary-color);
  border-radius: 15px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.8rem;
  color: white;
  box-shadow: 0 4px 15px rgba(0, 0, 0, 0.1);
}

.card-badge {
  display: flex;
  align-items: center;
  gap: 4px;
  background: var(--accent-color);
  color: white;
  padding: 4px 12px;
  border-radius: 15px;
  font-size: 0.8rem;
  font-weight: 600;
  position: absolute;
  top: 1rem;
  right: 1rem;
}

.module-content {
  padding: 0 2rem 1rem;
  flex: 1;
}

.module-content h3 {
  color: var(--text-primary);
  margin-bottom: 0.8rem;
  font-size: 1.4rem;
  font-weight: 600;
}

.module-content p {
  color: var(--text-secondary);
  margin-bottom: 1.5rem;
  line-height: 1.6;
  font-size: 0.95rem;
}

.module-stats {
  display: flex;
  gap: 1.5rem;
  margin-bottom: 1.5rem;
  flex-wrap: wrap;
}

.stat {
  display: flex;
  align-items: center;
  gap: 4px;
  font-size: 0.85rem;
  color: var(--text-secondary);
}

.stat i {
  color: var(--primary-color);
}

.module-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
}

.tag {
  background: var(--primary-light);
  color: var(--primary-color);
  padding: 0.3rem 0.8rem;
  border-radius: 15px;
  font-size: 0.8rem;
  font-weight: 500;
}

.module-footer {
  padding: 1.5rem 2rem 2rem;
  border-top: 1px solid var(--border-color);
  background: var(--bg-primary);
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.difficulty-price {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.difficulty {
  padding: 0.4rem 1rem;
  border-radius: 15px;
  font-size: 0.8rem;
  font-weight: 600;
  text-transform: uppercase;
  text-align: center;
}

.difficulty.easy {
  background: var(--success-light);
  color: var(--success-color);
}

.difficulty.medium {
  background: var(--warning-light);
  color: var(--warning-color);
}

.difficulty.hard {
  background: var(--error-light);
  color: var(--error-color);
}

.price {
  font-size: 1.1rem;
  font-weight: 700;
  color: var(--success-color);
  text-align: center;
}

.module-btn {
  display: flex;
  align-items: center;
  gap: 8px;
  background: var(--primary-color);
  color: white;
  border: none;
  padding: 12px 24px;
  border-radius: 25px;
  cursor: pointer;
  font-weight: 600;
  transition: all 0.3s ease;
  text-decoration: none;
  font-size: 0.95rem;
}

.module-btn:hover {
  background: var(--primary-dark);
  transform: translateY(-2px);
  box-shadow: 0 4px 15px rgba(0, 0, 0, 0.2);
}

/* 加载骨架屏 */
.skeleton {
  background: linear-gradient(
    90deg,
    var(--bg-tertiary) 25%,
    var(--bg-secondary) 50%,
    var(--bg-tertiary) 75%
  );
  background-size: 200% 100%;
  animation: skeleton-loading 1.5s infinite;
}

.skeleton-image {
  width: 100%;
  height: 200px;
  border-radius: var(--radius-lg) var(--radius-lg) 0 0;
}

.skeleton-content {
  padding: var(--spacing-lg);
}

.skeleton-title {
  height: 20px;
  margin-bottom: var(--spacing-sm);
  border-radius: var(--radius-sm);
}

.skeleton-text {
  height: 16px;
  margin-bottom: var(--spacing-xs);
  border-radius: var(--radius-sm);
}

.skeleton-text:last-child {
  width: 70%;
}

.skeleton-footer {
  height: 40px;
  margin-top: var(--spacing-md);
  border-radius: var(--radius-sm);
}

@keyframes skeleton-loading {
  0% {
    background-position: 200% 0;
  }
  100% {
    background-position: -200% 0;
  }
}

/* 返回顶部按钮 */
.back-to-top {
  position: fixed;
  bottom: var(--spacing-xl);
  right: var(--spacing-xl);
  width: 50px;
  height: 50px;
  background: var(--primary-color);
  color: var(--text-white);
  border: none;
  border-radius: var(--radius-full);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  box-shadow: var(--shadow-lg);
  opacity: 0;
  visibility: hidden;
  transform: translateY(20px);
  transition: all var(--transition-normal);
  z-index: 1000;
}

.back-to-top.show {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}

.back-to-top:hover {
  background: var(--primary-hover);
  transform: translateY(-2px);
}

/* 加载提示 */
.loading {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: var(--bg-overlay);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  z-index: 3000;
}

.loading-spinner {
  width: 40px;
  height: 40px;
  border: 4px solid var(--border-color);
  border-top: 4px solid var(--primary-color);
  border-radius: var(--radius-full);
  animation: spin 1s linear infinite;
  margin-bottom: var(--spacing-md);
}

@keyframes spin {
  0% {
    transform: rotate(0deg);
  }
  100% {
    transform: rotate(360deg);
  }
}

.loading p {
  color: var(--text-white);
  font-size: var(--text-lg);
  margin: 0;
}

/* ===== HERO SECTION ===== */
.hero {
  background: linear-gradient(
    135deg,
    var(--primary-color) 0%,
    var(--secondary-color) 100%
  );
  color: white;
  padding: 120px 0;
  text-align: center;
  position: relative;
  overflow: hidden;
  min-height: 100vh;
  display: flex;
  align-items: center;
}

.hero-background {
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  z-index: 1;
}

.hero-particles {
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: url('data:image/svg+xml,<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 100 100"><defs><pattern id="grain" width="100" height="100" patternUnits="userSpaceOnUse"><circle cx="50" cy="50" r="1" fill="%23ffffff" opacity="0.1"/></pattern></defs><rect width="100" height="100" fill="url(%23grain)"/></svg>')
    repeat;
  opacity: 0.3;
  animation: float 20s ease-in-out infinite;
}

.hero-gradient {
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: radial-gradient(
    circle at 30% 70%,
    rgba(255, 255, 255, 0.1) 0%,
    transparent 50%
  );
}

@keyframes float {
  0%,
  100% {
    transform: translateY(0px);
  }
  50% {
    transform: translateY(-20px);
  }
}

.hero-content {
  position: relative;
  z-index: 2;
  max-width: 900px;
  margin: 0 auto;
  padding: 0 20px;
}

.hero-badge {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  background: rgba(255, 255, 255, 0.15);
  backdrop-filter: blur(10px);
  padding: 8px 20px;
  border-radius: 25px;
  font-size: 0.9rem;
  font-weight: 500;
  margin-bottom: 2rem;
  border: 1px solid rgba(255, 255, 255, 0.2);
}

.hero-title {
  font-size: 4rem;
  font-weight: 700;
  margin-bottom: 1.5rem;
  text-shadow: 0 2px 4px rgba(0, 0, 0, 0.3);
  line-height: 1.2;
}

.hero-title .highlight {
  background: linear-gradient(45deg, var(--accent-color), #ff6b6b);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  display: block;
}

.hero-description {
  font-size: 1.3rem;
  margin-bottom: 3rem;
  opacity: 0.95;
  line-height: 1.6;
  max-width: 600px;
  margin-left: auto;
  margin-right: auto;
}

.hero-stats {
  display: flex;
  justify-content: center;
  gap: 3rem;
  margin-bottom: 3rem;
}

.stat-item {
  text-align: center;
}

.stat-number {
  font-size: 2.5rem;
  font-weight: 700;
  color: var(--accent-color);
  display: block;
}

.stat-label {
  font-size: 1rem;
  opacity: 0.9;
  margin-top: 0.5rem;
}

.hero-actions {
  display: flex;
  justify-content: center;
  gap: 1.5rem;
  margin-bottom: 4rem;
  flex-wrap: wrap;
}

.cta-button {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 15px 30px;
  font-size: 1.1rem;
  font-weight: 600;
  border-radius: 50px;
  cursor: pointer;
  transition: all 0.3s ease;
  text-decoration: none;
  border: 2px solid transparent;
  min-width: 160px;
  justify-content: center;
}

.cta-button.primary {
  background: var(--accent-color);
  color: white;
  border: none;
  box-shadow: 0 4px 15px rgba(0, 0, 0, 0.2);
}

.cta-button.primary:hover {
  background: var(--accent-hover);
  transform: translateY(-2px);
  box-shadow: 0 6px 20px rgba(0, 0, 0, 0.3);
}

.cta-button.secondary {
  background: transparent;
  color: white;
  border: 2px solid rgba(255, 255, 255, 0.3);
  backdrop-filter: blur(10px);
}

.cta-button.secondary:hover {
  background: rgba(255, 255, 255, 0.1);
  border-color: rgba(255, 255, 255, 0.5);
  transform: translateY(-2px);
}

.hero-features {
  display: flex;
  justify-content: center;
  gap: 2rem;
  flex-wrap: wrap;
}

.feature-item {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 1rem;
  opacity: 0.9;
}

.feature-item i {
  color: var(--accent-color);
}

/* ===== FEATURES SECTION ===== */
.features {
  padding: 80px 0;
  background: var(--bg-primary);
}

.features-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 2rem;
  max-width: 1200px;
  margin: 0 auto;
}

.feature-card {
  background: var(--card-bg);
  border-radius: 20px;
  padding: 2.5rem 2rem;
  text-align: center;
  box-shadow: var(--shadow-card);
  border: 1px solid var(--border-color);
  transition: all 0.3s ease;
  position: relative;
  overflow: hidden;
}

.feature-card::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 4px;
  background: linear-gradient(90deg, var(--primary-color), var(--accent-color));
  transform: scaleX(0);
  transition: transform 0.3s ease;
}

.feature-card:hover::before {
  transform: scaleX(1);
}

.feature-card:hover {
  transform: translateY(-5px);
  box-shadow: var(--shadow-hover);
}

.feature-icon {
  width: 80px;
  height: 80px;
  background: linear-gradient(
    135deg,
    var(--primary-color),
    var(--secondary-color)
  );
  border-radius: 20px;
  display: flex;
  align-items: center;
  justify-content: center;
  margin: 0 auto 1.5rem;
  font-size: 2rem;
  color: white;
  box-shadow: 0 8px 25px rgba(0, 0, 0, 0.1);
}

.feature-card h3 {
  color: var(--text-primary);
  font-size: 1.4rem;
  font-weight: 600;
  margin-bottom: 1rem;
}

.feature-card p {
  color: var(--text-secondary);
  line-height: 1.6;
  margin-bottom: 1.5rem;
}

.feature-list {
  list-style: none;
  padding: 0;
  text-align: left;
}

.feature-list li {
  display: flex;
  align-items: center;
  gap: 8px;
  color: var(--text-secondary);
  margin-bottom: 0.8rem;
  font-size: 0.95rem;
}

.feature-list li i {
  color: var(--success-color);
  font-size: 0.9rem;
}

/* ===== FOOTER ===== */
.footer {
  background: var(--bg-dark);
  color: var(--text-light);
  margin-top: auto;
}

.footer-content {
  padding: 4rem 0 2rem;
}

.footer-grid {
  display: grid;
  grid-template-columns: 2fr 1fr 1fr 1fr;
  gap: 3rem;
  max-width: 1200px;
  margin: 0 auto;
}

.footer-section h4 {
  color: white;
  font-size: 1.2rem;
  font-weight: 600;
  margin-bottom: 1.5rem;
}

.footer-logo {
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 1.5rem;
  font-weight: 700;
  color: white;
  margin-bottom: 1rem;
}

.footer-logo i {
  color: var(--accent-color);
}

.footer-description {
  color: var(--text-light);
  line-height: 1.6;
  margin-bottom: 2rem;
  opacity: 0.9;
}

.footer-social {
  display: flex;
  gap: 1rem;
}

.social-link {
  width: 40px;
  height: 40px;
  background: rgba(255, 255, 255, 0.1);
  border-radius: 10px;
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--text-light);
  text-decoration: none;
  transition: all 0.3s ease;
}

.social-link:hover {
  background: var(--accent-color);
  color: white;
  transform: translateY(-2px);
}

.footer-links {
  list-style: none;
  padding: 0;
}

.footer-links li {
  margin-bottom: 0.8rem;
}

.footer-links a {
  color: var(--text-light);
  text-decoration: none;
  transition: all 0.3s ease;
  display: flex;
  align-items: center;
  gap: 8px;
  opacity: 0.9;
}

.footer-links a:hover {
  color: var(--accent-color);
  opacity: 1;
  transform: translateX(5px);
}

.footer-links a i {
  font-size: 0.8rem;
  opacity: 0.7;
}

.contact-info {
  display: flex;
  flex-direction: column;
  gap: 1rem;
}

.contact-item {
  display: flex;
  align-items: center;
  gap: 10px;
  color: var(--text-light);
  opacity: 0.9;
}

.contact-item i {
  color: var(--accent-color);
  width: 16px;
}

.footer-bottom {
  border-top: 1px solid rgba(255, 255, 255, 0.1);
  padding: 2rem 0;
}

.footer-bottom-content {
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 1rem;
}

.copyright {
  color: var(--text-light);
  opacity: 0.8;
}

.footer-legal {
  display: flex;
  gap: 2rem;
  flex-wrap: wrap;
}

.footer-legal label {
  color: var(--text-light);
  opacity: 0.8;
  font-size: 0.9rem;
}

.footer-legal a {
  color: #3498db;
  text-decoration: none;
  transition: color 0.3s ease;
  font-weight: 500;
}

.footer-legal a:hover {
  color: #ffffff;
  text-decoration: underline;
}

/* ===== LOGIN HINTS ===== */
.module-actions {
  display: flex;
  flex-direction: column;
  gap: 0.8rem;
}

.login-hint {
  display: flex;
  align-items: center;
  gap: 6px;
  font-size: 0.85rem;
  color: var(--text-secondary);
  opacity: 0.8;
  transition: opacity 0.3s ease;
}

.login-hint:hover {
  opacity: 1;
}

.login-hint i {
  color: var(--primary-color);
  font-size: 0.8rem;
}

.login-hint a {
  color: var(--primary-color);
  text-decoration: none;
  font-weight: 500;
  transition: color 0.3s ease;
}

.login-hint a:hover {
  color: var(--accent-color);
  text-decoration: underline;
}

.community-actions {
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  gap: 1rem;
}

.login-required-hint {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 0.8rem 1.2rem;
  background: rgba(var(--primary-color-rgb), 0.1);
  border: 1px solid rgba(var(--primary-color-rgb), 0.2);
  border-radius: 8px;
  font-size: 0.9rem;
  color: var(--text-secondary);
  transition: all 0.3s ease;
}

.login-required-hint:hover {
  background: rgba(var(--primary-color-rgb), 0.15);
  border-color: rgba(var(--primary-color-rgb), 0.3);
}

.login-required-hint i {
  color: var(--primary-color);
  font-size: 0.85rem;
}

.login-required-hint a {
  color: var(--primary-color);
  text-decoration: none;
  font-weight: 600;
  transition: color 0.3s ease;
}

.login-required-hint a:hover {
  color: var(--accent-color);
  text-decoration: underline;
}

/* 响应式设计 */
@media (max-width: 768px) {
  .hero {
    padding: 80px 0;
    min-height: 80vh;
  }

  .hero-title {
    font-size: 2.5rem;
  }

  .hero-description {
    font-size: 1.1rem;
  }

  .hero-stats {
    gap: 1.5rem;
  }

  .stat-number {
    font-size: 2rem;
  }

  .hero-actions {
    flex-direction: column;
    align-items: center;
  }

  .hero-features {
    flex-direction: column;
    gap: 1rem;
  }

  .features-grid {
    grid-template-columns: 1fr;
    gap: 1.5rem;
  }

  .footer-grid {
    grid-template-columns: 1fr;
    gap: 2rem;
    text-align: center;
  }

  .footer-bottom-content {
    flex-direction: column;
    text-align: center;
  }

  .footer-legal {
    flex-direction: column;
    gap: 1rem;
  }

  .community-actions {
    align-items: center;
    text-align: center;
  }

  .login-required-hint {
    padding: 0.6rem 1rem;
    font-size: 0.85rem;
  }

  .module-actions {
    gap: 0.6rem;
  }

  .login-hint {
    font-size: 0.8rem;
    justify-content: center;
  }
}

@media (max-width: 768px) {
  .nav-menu {
    position: fixed;
    top: 100%;
    left: 0;
    width: 100%;
    background: var(--bg-primary);
    border-top: 1px solid var(--border-color);
    box-shadow: var(--shadow-lg);
    opacity: 0;
    visibility: hidden;
    transform: translateY(-10px);
    transition: all var(--transition-normal);
  }

  .nav-menu.show {
    opacity: 1;
    visibility: visible;
    transform: translateY(0);
  }

  .nav-list {
    flex-direction: column;
    padding: var(--spacing-lg);
    gap: var(--spacing-sm);
  }

  .nav-link {
    padding: var(--spacing-md);
    text-align: center;
  }

  .nav-toggle {
    display: flex;
  }

  .auth-buttons {
    flex-direction: column;
    gap: var(--spacing-xs);
  }

  .course-filters {
    justify-content: flex-start;
    overflow-x: auto;
    padding-bottom: var(--spacing-sm);
  }

  .filter-btn {
    white-space: nowrap;
  }

  .modal-content {
    width: 95%;
    margin: var(--spacing-md);
  }

  .back-to-top {
    bottom: var(--spacing-lg);
    right: var(--spacing-lg);
    width: 45px;
    height: 45px;
  }
}

@media (max-width: 480px) {
  .nav-container {
    padding: var(--spacing-sm) var(--spacing-md);
  }

  .btn-large {
    padding: var(--spacing-sm) var(--spacing-lg);
    font-size: var(--text-sm);
  }

  .course-card {
    margin-bottom: var(--spacing-md);
  }

  .course-content {
    padding: var(--spacing-md);
  }

  .modal-header,
  .modal-body,
  .modal-footer {
    padding: var(--spacing-md);
  }
}

/* 强制深绿色主题覆盖 */
.navbar {
  background: rgba(13, 17, 23, 0.95) !important;
  backdrop-filter: blur(10px);
  border-bottom: 1px solid #30363d !important;
}

.navbar.scrolled {
  background: rgba(13, 17, 23, 0.98) !important;
  box-shadow: 0 4px 6px rgba(0, 0, 0, 0.3) !important;
}

/* 导航链接深绿色 */
.nav-link, .brand-link {
  color: #28a745 !important;
}

.nav-link:hover, .brand-link:hover {
  color: #34ce57 !important;
}

/* 卡片和组件深色背景 */
.card, .hero-section, .features-section, .course-card {
  background-color: #161b22 !important;
  border-color: #30363d !important;
}

/* 按钮组件深绿色主题 */
.btn-primary {
  background-color: #28a745 !important;
  border-color: #28a745 !important;
  color: #0d1117 !important;
}

.btn-primary:hover {
  background-color: #34ce57 !important;
  border-color: #34ce57 !important;
}

.btn-secondary {
  background-color: #20c997 !important;
  border-color: #20c997 !important;
  color: #0d1117 !important;
}

.btn-secondary:hover {
  background-color: #40e0d0 !important;
  border-color: #40e0d0 !important;
}