/* 基础样式重置 */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    line-height: 1.6;
    color: #333;
    background-color: #fafafa;
}

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

/* 导航栏样式 */
.navbar {
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(10px);
    padding: 0.8rem 0;
    position: fixed;
    top: 0;
    width: 100%;
    z-index: 1000;
    border-bottom: 1px solid rgba(0, 0, 0, 0.1);
}

.nav-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    height: 80px;
}

.nav-logo {
    display: flex;
    flex-direction: column;
    align-items: flex-start;
    color: #2563eb;
}

.logo-main {
    display: flex;
    align-items: center;
    margin-bottom: 0.2rem;
}

.nav-logo i {
    font-size: 1.8rem;
    margin-right: 0.5rem;
    color: #2563eb;
}

.nav-logo span {
    font-size: 1.6rem;
    font-weight: 700;
    color: #2563eb;
}

.nav-logo small {
    font-size: 1.2rem;
    font-weight: 600;
    color: #4f46e5;
    white-space: nowrap;
    line-height: 1.1;
}

.nav-menu {
    display: flex;
    list-style: none;
    gap: 30px;
}

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

.nav-link:hover {
    color: #3182ce;
}

.hamburger {
    display: none;
    flex-direction: column;
    cursor: pointer;
}

.hamburger span {
    width: 25px;
    height: 3px;
    background: #333;
    margin: 3px 0;
    transition: 0.3s;
}

/* Banner样式 */
.banner {
    background: linear-gradient(rgba(0, 0, 0, 0.4), rgba(0, 0, 0, 0.4)), url('aa.jpg');
    background-size: cover;
    background-position: center;
    background-attachment: fixed;
    height: 70vh;
    display: flex;
    align-items: center;
    justify-content: center;
    text-align: center;
    color: white;
    position: relative;
}

.banner-overlay {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(26, 54, 93, 0.7);
    z-index: 1;
}

.banner-content {
    position: relative;
    z-index: 2;
    max-width: 800px;
    padding: 0 20px;
}

.banner-content h1 {
    font-size: 3.5rem;
    font-weight: 700;
    margin-bottom: 1rem;
    text-shadow: 2px 2px 4px rgba(0, 0, 0, 0.5);
}

.banner-content h2 {
    font-size: 1.8rem;
    font-weight: 400;
    margin-bottom: 2rem;
    max-width: 800px;
    text-shadow: 1px 1px 2px rgba(0, 0, 0, 0.5);
}

/* 承诺样式 */
.commitment {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 10px;
    margin-bottom: 2rem;
    background: rgba(255, 255, 255, 0.1);
    backdrop-filter: blur(10px);
    padding: 15px 25px;
    border-radius: 25px;
    border: 1px solid rgba(255, 255, 255, 0.2);
}

.commitment i {
    font-size: 1.5rem;
    color: #ffd700;
}

.commitment p {
    font-size: 1.1rem;
    font-weight: 600;
    margin: 0;
}

.cta-buttons {
    display: flex;
    gap: 20px;
    justify-content: center;
    flex-wrap: wrap;
}

/* 按钮样式 */
.btn {
    display: inline-block;
    padding: 15px 30px;
    border-radius: 8px;
    text-decoration: none;
    font-weight: 600;
    transition: all 0.3s ease;
    border: none;
    cursor: pointer;
    font-size: 1rem;
}

.btn-primary {
    background: #3182ce;
    color: white;
}

.btn-primary:hover {
    background: #2c5aa0;
    transform: translateY(-2px);
}

.btn-secondary {
    background: rgba(255, 255, 255, 0.2);
    color: white;
    border: 2px solid rgba(255, 255, 255, 0.3);
}

.btn-secondary:hover {
    background: rgba(255, 255, 255, 0.3);
    transform: translateY(-2px);
}

.btn-outline {
    background: transparent;
    color: #3182ce;
    border: 2px solid #3182ce;
}

.btn-outline:hover {
    background: #3182ce;
    color: white;
}

/* 课程部分样式 */
.courses-section {
    padding: 80px 0;
    background: #f8f9fa;
}

.section-header {
    text-align: center;
    margin-bottom: 50px;
}

.section-header h2 {
    font-size: 2.5rem;
    color: #2d3748;
    margin-bottom: 10px;
}

.section-header p {
    font-size: 1.2rem;
    color: #718096;
}

/* 筛选器样式 */
.filter-tabs {
    display: flex;
    justify-content: center;
    gap: 20px;
    margin-bottom: 30px;
}

.filter-btn {
    padding: 15px 30px;
    background: white;
    border: 2px solid #e2e8f0;
    border-radius: 8px;
    color: #4a5568;
    font-weight: 600;
    font-size: 1.3rem;
    cursor: pointer;
    transition: all 0.3s ease;
}

.filter-btn.active, .filter-btn:hover {
    background: #3182ce;
    color: white;
    border-color: #3182ce;
    transform: translateY(-2px);
}

.filter-buttons {
    display: flex;
    justify-content: center;
    gap: 12px;
    margin-bottom: 40px;
    flex-wrap: wrap;
    max-width: 1200px;
    margin-left: auto;
    margin-right: auto;
}

.category-btn, .country-btn {
    padding: 10px 18px;
    background: white;
    border: 2px solid #e2e8f0;
    border-radius: 25px;
    color: #4a5568;
    font-weight: 600;
    font-size: 1.1rem;
    cursor: pointer;
    transition: all 0.3s ease;
    display: flex;
    align-items: center;
    gap: 6px;
    white-space: nowrap;
    min-width: fit-content;
}

.category-btn:hover, .country-btn:hover {
    background: #f7fafc;
    border-color: #3182ce;
    color: #3182ce;
    transform: translateY(-2px);
}

.category-btn.active, .country-btn.active {
    background: #3182ce;
    color: white;
    border-color: #3182ce;
    transform: translateY(-2px);
}

/* 类别和国家部分样式 */
.category-section, .country-section {
    margin-bottom: 50px;
}

.category-header, .country-header {
    margin-bottom: 30px;
    text-align: center;
}

.category-header h3, .country-header h3 {
    font-size: 1.8rem;
    color: #2d3748;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 10px;
    margin-bottom: 10px;
}

.category-header i, .country-header i {
    color: #3182ce;
}

.course-count {
    font-size: 1rem;
    color: #718096;
    font-weight: normal;
}

/* 4x4网格布局 */
.courses-grid {
    display: grid;
    gap: 25px;
    margin-bottom: 30px;
}

.grid-4x4 {
    grid-template-columns: repeat(4, 1fr);
}

/* 课程卡片样式 */
.course-card {
    background: white;
    border-radius: 12px;
    padding: 20px;
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
    transition: all 0.3s ease;
    border: 1px solid #e2e8f0;
    height: 100%;
    display: flex;
    flex-direction: column;
}

.course-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 10px 25px rgba(0, 0, 0, 0.15);
    border-color: #3182ce;
}

.course-header {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    margin-bottom: 15px;
    gap: 10px;
}

.course-code {
    background: #3182ce;
    color: white;
    padding: 4px 12px;
    border-radius: 6px;
    font-size: 0.85rem;
    font-weight: 600;
    white-space: nowrap;
    flex-shrink: 0;
}

.university {
    font-size: 0.9rem;
    color: #718096;
    text-align: right;
    line-height: 1.3;
    font-weight: 500;
}

.course-content {
    flex-grow: 1;
    margin-bottom: 20px;
}

.course-title {
    font-size: 1.1rem;
    font-weight: 600;
    color: #2d3748;
    margin-bottom: 10px;
    line-height: 1.4;
    display: -webkit-box;
    -webkit-line-clamp: 2;
    -webkit-box-orient: vertical;
    overflow: hidden;
}

.course-description {
    font-size: 0.9rem;
    color: #718096;
    line-height: 1.5;
    display: -webkit-box;
    -webkit-line-clamp: 3;
    -webkit-box-orient: vertical;
    overflow: hidden;
}

.course-footer {
    margin-top: auto;
}

.course-footer .contact-btn {
    width: 100%;
    padding: 10px 15px;
    background: #3182ce;
    color: white;
    border: none;
    border-radius: 6px;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
}

.course-footer .contact-btn:hover {
    background: #2c5aa0;
    transform: translateY(-1px);
}

/* Load More 按钮样式 */
.load-more-container {
    display: flex;
    justify-content: center;
    margin: 40px 0;
}

.load-more-btn {
    padding: 15px 30px;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    border: none;
    border-radius: 25px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
    display: flex;
    align-items: center;
    gap: 10px;
    min-width: 200px;
    justify-content: center;
}

.load-more-btn:hover {
    transform: translateY(-2px);
    box-shadow: 0 8px 25px rgba(102, 126, 234, 0.4);
}

.load-more-btn:disabled {
    opacity: 0.6;
    cursor: not-allowed;
    transform: none;
}

.load-more-btn:disabled:hover {
    transform: none;
    box-shadow: none;
}

/* 加载状态样式 */
.loading-container {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: 60px 20px;
    color: #718096;
}

.loading-spinner {
    margin-bottom: 20px;
}

.loading-spinner i {
    font-size: 2rem;
    color: #3182ce;
}

/* 错误状态样式 */
.error-container {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: 60px 20px;
    text-align: center;
}

.error-icon {
    margin-bottom: 20px;
}

.error-icon i {
    font-size: 3rem;
    color: #e53e3e;
}

.error-container h3 {
    font-size: 1.5rem;
    color: #2d3748;
    margin-bottom: 10px;
}

.error-container p {
    color: #718096;
    margin-bottom: 20px;
}

.retry-btn {
    padding: 12px 24px;
    background: #3182ce;
    color: white;
    border: none;
    border-radius: 6px;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
    display: flex;
    align-items: center;
    gap: 8px;
}

.retry-btn:hover {
    background: #2c5aa0;
    transform: translateY(-1px);
}

/* Toast 通知样式 */
.toast-notification {
    position: fixed;
    top: 100px;
    right: 20px;
    background: #48bb78;
    color: white;
    padding: 15px 20px;
    border-radius: 8px;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.2);
    display: flex;
    align-items: center;
    gap: 10px;
    font-weight: 600;
    z-index: 10000;
    transform: translateX(100%);
    transition: transform 0.3s ease;
}

.toast-notification.show {
    transform: translateX(0);
}

.toast-notification i {
    font-size: 1.2rem;
}

/* 联系部分样式 */
.contact-section {
    padding: 80px 0;
    background: white;
}

.browse-courses-btn {
    margin-top: 25px;
    padding: 15px 30px;
    font-size: 1.1rem;
    display: inline-flex;
    align-items: center;
    gap: 10px;
    text-decoration: none;
    border-radius: 8px;
    transition: all 0.3s ease;
}

.browse-courses-btn:hover {
    transform: translateY(-3px);
    box-shadow: 0 8px 25px rgba(49, 130, 206, 0.4);
}

.contact-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 30px;
    margin-top: 50px;
}

.contact-card {
    background: #f8f9fa;
    padding: 40px 30px;
    border-radius: 12px;
    text-align: center;
    transition: all 0.3s ease;
    border: 2px solid transparent;
}

.contact-card:hover {
    transform: translateY(-5px);
    border-color: #3182ce;
    background: white;
}

.contact-icon {
    width: 70px;
    height: 70px;
    background: #3182ce;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    margin: 0 auto 20px;
}

.contact-icon i {
    font-size: 1.8rem;
    color: white;
}

.contact-card h3 {
    font-size: 1.3rem;
    margin-bottom: 10px;
    color: #2d3748;
}

.contact-value {
    font-size: 1.1rem;
    color: #3182ce;
    font-weight: 600;
    margin-bottom: 20px;
}

.contact-btn {
    padding: 10px 20px;
    background: #3182ce;
    color: white;
    border: none;
    border-radius: 6px;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
}

.contact-btn:hover {
    background: #2c5aa0;
    transform: translateY(-1px);
}

.contact-btn i {
    margin-right: 8px;
}

/* 关于我们样式 */
.about-section {
    padding: 80px 0;
    background: white;
}

.about-content {
    display: grid;
    grid-template-columns: 2fr 1fr;
    gap: 50px;
    align-items: start;
}

.about-text h3 {
    font-size: 2rem;
    color: #2d3748;
    margin-bottom: 20px;
}

.about-text p {
    font-size: 1rem;
    color: #718096;
    margin-bottom: 20px;
    line-height: 1.8;
}

.about-features {
    display: grid;
    gap: 30px;
}

.feature {
    text-align: center;
    padding: 20px;
    background: #f8f9fa;
    border-radius: 8px;
}

.feature i {
    font-size: 2rem;
    color: #3182ce;
    margin-bottom: 15px;
}

.feature h4 {
    font-size: 1.1rem;
    color: #2d3748;
    margin-bottom: 10px;
}

.feature p {
    color: #718096;
    font-size: 0.9rem;
}

/* 侧边栏联系方式 */
.contact-sidebar {
    position: fixed;
    right: 20px;
    bottom: 20px;
    background: white;
    border-radius: 12px;
    box-shadow: 0 8px 25px rgba(0, 0, 0, 0.15);
    width: 280px;
    z-index: 1000;
    overflow: hidden;
    border: 1px solid #e2e8f0;
}

.sidebar-header {
    background: #3182ce;
    color: white;
    padding: 15px 20px;
    display: flex;
    align-items: center;
    gap: 10px;
    font-weight: 600;
}

.sidebar-header i {
    font-size: 1.2rem;
}

.contact-item {
    padding: 15px 20px;
    border-bottom: 1px solid #e2e8f0;
    cursor: pointer;
    transition: all 0.3s ease;
    display: flex;
    align-items: center;
    gap: 15px;
}

.contact-item:last-child {
    border-bottom: none;
}

.contact-item:hover {
    background: #f8f9fa;
}

.contact-item-icon {
    width: 40px;
    height: 40px;
    background: #f8f9fa;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    flex-shrink: 0;
}

.contact-item-icon i {
    font-size: 1.1rem;
    color: #3182ce;
}

.contact-item-info {
    flex-grow: 1;
}

.contact-item-info span {
    display: block;
    font-size: 0.8rem;
    color: #718096;
    margin-bottom: 2px;
}

.contact-item-info strong {
    font-size: 0.9rem;
    color: #2d3748;
    font-weight: 600;
}

.contact-item-action {
    width: 30px;
    height: 30px;
    background: #3182ce;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    opacity: 0;
    transition: all 0.3s ease;
    flex-shrink: 0;
}

.contact-item:hover .contact-item-action {
    opacity: 1;
}

.contact-item-action i {
    font-size: 0.8rem;
    color: white;
}

/* 页脚样式 */
.footer {
    background: #2d3748;
    color: white;
    padding: 40px 0 20px;
}

.footer-content {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 40px;
}

.footer-section h4 {
    font-size: 1.2rem;
    margin-bottom: 15px;
    color: #e2e8f0;
}

.footer-section ul {
    list-style: none;
}

.footer-section ul li {
    margin-bottom: 8px;
    color: #a0aec0;
}

.footer-btn {
    margin-top: 20px;
    background: transparent;
    color: #e2e8f0;
    border: 2px solid #e2e8f0;
    padding: 12px 20px;
    border-radius: 6px;
    text-decoration: none;
    display: inline-flex;
    align-items: center;
    gap: 8px;
    font-weight: 600;
    transition: all 0.3s ease;
}

.footer-btn:hover {
    background: #e2e8f0;
    color: #2d3748;
    transform: translateY(-2px);
}

.footer-bottom {
    text-align: center;
    margin-top: 30px;
    padding-top: 20px;
    border-top: 1px solid #4a5568;
    color: #a0aec0;
}

/* 交易流程弹窗样式 */
.modal-overlay {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(0, 0, 0, 0.7);
    z-index: 10000;
    display: flex;
    align-items: center;
    justify-content: center;
    opacity: 0;
    visibility: hidden;
    transition: all 0.3s ease;
}

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

.modal-content {
    background: white;
    border-radius: 16px;
    max-width: 600px;
    width: 90%;
    max-height: 80vh;
    overflow-y: auto;
    position: relative;
    transform: translateY(50px);
    transition: transform 0.3s ease;
}

.modal-overlay.show .modal-content {
    transform: translateY(0);
}

.modal-header {
    background: linear-gradient(135deg, #3182ce 0%, #667eea 100%);
    color: white;
    padding: 20px 30px;
    border-radius: 16px 16px 0 0;
    position: relative;
}

.modal-header h3 {
    font-size: 1.5rem;
    margin: 0;
    display: flex;
    align-items: center;
    gap: 10px;
}

.modal-close {
    position: absolute;
    top: 20px;
    right: 30px;
    background: none;
    border: none;
    color: white;
    font-size: 1.5rem;
    cursor: pointer;
    padding: 5px;
    border-radius: 50%;
    transition: all 0.3s ease;
}

.modal-close:hover {
    background: rgba(255, 255, 255, 0.2);
    transform: rotate(90deg);
}

.modal-body {
    padding: 30px;
}

.process-steps {
    display: grid;
    gap: 20px;
}

.process-step {
    display: flex;
    align-items: flex-start;
    gap: 15px;
    padding: 20px;
    background: #f8f9fa;
    border-radius: 12px;
    border-left: 4px solid #3182ce;
    transition: all 0.3s ease;
}

.process-step:hover {
    background: #e8f4fd;
    transform: translateX(5px);
}

.step-number {
    background: #3182ce;
    color: white;
    width: 30px;
    height: 30px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: bold;
    font-size: 0.9rem;
    flex-shrink: 0;
}

.step-content h4 {
    color: #2d3748;
    margin-bottom: 8px;
    font-size: 1.1rem;
    display: flex;
    align-items: center;
    gap: 8px;
}

.step-content p {
    color: #718096;
    line-height: 1.6;
    margin: 0;
}

.modal-footer {
    padding: 20px 30px;
    border-top: 1px solid #e2e8f0;
    display: flex;
    justify-content: center;
}

.modal-btn {
    background: #3182ce;
    color: white;
    border: none;
    padding: 12px 30px;
    border-radius: 8px;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
    display: flex;
    align-items: center;
    gap: 8px;
}

.modal-btn:hover {
    background: #2c5aa0;
    transform: translateY(-1px);
}

/* 响应式设计 */
@media (max-width: 1199px) {
    .grid-4x4 {
        grid-template-columns: repeat(3, 1fr);
    }
}

@media (max-width: 991px) {
    .grid-4x4 {
        grid-template-columns: repeat(2, 1fr);
    }

    .contact-sidebar {
        display: none;
    }

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

@media (max-width: 767px) {
    .grid-4x4 {
        grid-template-columns: 1fr;
    }
    
    .filter-buttons {
        flex-direction: column;
        align-items: center;
    }
    
    .category-btn, .country-btn {
        min-width: 200px;
        justify-content: center;
    }
    
    .contact-sidebar {
        position: static;
        width: 100%;
        margin-top: 20px;
    }
    
    .footer-content {
        grid-template-columns: 1fr;
        text-align: center;
    }
    
    .contact-grid {
        grid-template-columns: 1fr;
    }
    
    .banner-content h1 {
        font-size: 2.5rem;
    }
    
    .banner-content h2 {
        font-size: 1.4rem;
    }
}

@media (max-width: 575px) {
    .nav-logo span {
        font-size: 1.3rem;
    }
    
    .nav-logo small {
        font-size: 1rem;
    }
    
    .banner-content h1 {
        font-size: 2rem;
    }
    
    .banner-content h2 {
        font-size: 1.2rem;
    }
    
    .load-more-btn {
        font-size: 0.9rem;
        padding: 12px 20px;
        min-width: 180px;
    }
}

/* 动画效果 */
@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(30px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.course-card {
    animation: fadeInUp 0.6s ease forwards;
}

.course-card:nth-child(odd) {
    animation-delay: 0.1s;
}

.course-card:nth-child(even) {
    animation-delay: 0.2s;
}

/* 滚动条样式 */
::-webkit-scrollbar {
    width: 8px;
}

::-webkit-scrollbar-track {
    background: #f1f1f1;
}

::-webkit-scrollbar-thumb {
    background: #c1c1c1;
    border-radius: 4px;
}

::-webkit-scrollbar-thumb:hover {
    background: #a8a8a8;
}

/* 平滑滚动 */
html {
    scroll-behavior: smooth;
}

/* 隐藏课程样式 */
.course-card.hidden-course {
    display: none;
}

/* 课程卡片动画 */
@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(30px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.course-card {
    animation: fadeInUp 0.6s ease forwards;
}

.course-card:nth-child(odd) {
    animation-delay: 0.1s;
}

.course-card:nth-child(even) {
    animation-delay: 0.2s;
}

/* 课程展示区域布局 */
.courses-display-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
}