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

:root {
    --primary: #1e5fbf;
    --primary-dark: #154a96;
    --primary-light: #3d7fd9;
    --secondary: #f5a623;
    --accent: #e74c3c;
    --text-dark: #1a2a4a;
    --text-medium: #4a5a7a;
    --text-light: #8a94a6;
    --bg-light: #f4f7fc;
    --bg-white: #ffffff;
    --bg-gray: #eef2f8;
    --border: #e1e7f0;
    --shadow-sm: 0 2px 8px rgba(30, 95, 191, 0.06);
    --shadow-md: 0 8px 24px rgba(30, 95, 191, 0.08);
    --shadow-lg: 0 16px 48px rgba(30, 95, 191, 0.12);
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 20px;
    --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

html {
    scroll-behavior: smooth;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
    font-size: 16px;
    line-height: 1.7;
    color: var(--text-dark);
    background-color: var(--bg-white);
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 24px;
}

a {
    text-decoration: none;
    color: inherit;
    transition: var(--transition);
}

ul {
    list-style: none;
}

/* Header */
.header {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(10px);
    -webkit-backdrop-filter: blur(10px);
    z-index: 1000;
    box-shadow: var(--shadow-sm);
    transition: var(--transition);
}

.nav {
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 72px;
}

.logo {
    display: flex;
    align-items: center;
    gap: 12px;
    font-weight: 700;
    font-size: 1.2rem;
    color: var(--text-dark);
}

.logo-icon {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 40px;
    height: 40px;
    background: linear-gradient(135deg, var(--primary), var(--primary-light));
    color: white;
    font-size: 1.2rem;
    border-radius: var(--radius-sm);
    box-shadow: 0 4px 12px rgba(30, 95, 191, 0.3);
}

.logo-img {
    width: 45px;
    height: 45px;
    border-radius: 8px;
    object-fit: cover;
}

.nav-menu {
    display: flex;
    gap: 8px;
    align-items: center;
}

.nav-link {
    display: inline-block;
    padding: 10px 18px;
    border-radius: var(--radius-sm);
    font-weight: 500;
    color: var(--text-medium);
    font-size: 0.95rem;
}

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

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

.nav-toggle {
    display: none;
    flex-direction: column;
    gap: 5px;
    cursor: pointer;
    padding: 8px;
}

.nav-toggle span {
    width: 24px;
    height: 2px;
    background: var(--text-dark);
    border-radius: 2px;
    transition: var(--transition);
}

/* Hero */
.hero {
    position: relative;
    padding: 160px 0 100px;
    background: linear-gradient(135deg, #eef4ff 0%, #f4f7fc 50%, #eef4ff 100%);
    overflow: hidden;
}

.hero-decoration {
    position: absolute;
    top: 0;
    right: 0;
    width: 60%;
    height: 100%;
    background: radial-gradient(circle at 70% 50%, rgba(30, 95, 191, 0.12) 0%, transparent 60%);
    pointer-events: none;
}

.hero-content {
    position: relative;
    z-index: 1;
    max-width: 800px;
}

.hero-title {
    font-size: clamp(2rem, 5vw, 3.2rem);
    line-height: 1.25;
    color: var(--text-dark);
    font-weight: 800;
    margin-bottom: 20px;
}

.hero-highlight {
    color: var(--primary);
    position: relative;
    display: inline-block;
}

.hero-highlight::after {
    content: '';
    position: absolute;
    bottom: 4px;
    left: 0;
    right: 0;
    height: 10px;
    background: rgba(245, 166, 35, 0.25);
    z-index: -1;
    border-radius: 4px;
}

.hero-subtitle {
    font-size: 1.15rem;
    color: var(--text-medium);
    margin-bottom: 40px;
    max-width: 600px;
}

.hero-stats {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 20px;
    margin-bottom: 40px;
    max-width: 700px;
}

.stat-item {
    background: white;
    padding: 24px 16px;
    border-radius: var(--radius-md);
    text-align: center;
    box-shadow: var(--shadow-sm);
    transition: var(--transition);
}

.stat-item:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-md);
}

.stat-number {
    font-size: 2rem;
    font-weight: 800;
    color: var(--primary);
    line-height: 1;
    margin-bottom: 8px;
}

.stat-label {
    font-size: 0.85rem;
    color: var(--text-medium);
    font-weight: 500;
}

.hero-actions {
    display: flex;
    gap: 16px;
    flex-wrap: wrap;
}

.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 14px 32px;
    border-radius: var(--radius-sm);
    font-weight: 600;
    font-size: 1rem;
    cursor: pointer;
    transition: var(--transition);
    border: 2px solid transparent;
}

.btn-primary {
    background: var(--primary);
    color: white;
    box-shadow: 0 6px 20px rgba(30, 95, 191, 0.3);
}

.btn-primary:hover {
    background: var(--primary-dark);
    transform: translateY(-2px);
    box-shadow: 0 10px 28px rgba(30, 95, 191, 0.4);
}

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

.btn-secondary:hover {
    background: var(--primary);
    color: white;
    transform: translateY(-2px);
}

/* Section */
.section {
    padding: 100px 0;
}

.section-header {
    text-align: center;
    margin-bottom: 60px;
}

.section-tag {
    display: inline-block;
    padding: 6px 18px;
    background: rgba(30, 95, 191, 0.1);
    color: var(--primary);
    border-radius: 20px;
    font-size: 0.85rem;
    font-weight: 600;
    margin-bottom: 16px;
}

.section-title {
    font-size: clamp(1.8rem, 3.5vw, 2.5rem);
    color: var(--text-dark);
    font-weight: 800;
    margin-bottom: 12px;
}

.section-subtitle {
    font-size: 1.1rem;
    color: var(--text-medium);
}

/* About */
.about-section {
    background: white;
}

.about-grid {
    display: grid;
    grid-template-columns: 1fr 1.2fr;
    gap: 60px;
    align-items: center;
}

.about-image {
    position: relative;
}

.about-logo {
    width: 100%;
    max-width: 300px;
    aspect-ratio: 1;
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-lg);
}

.image-placeholder {
    width: 100%;
    aspect-ratio: 4 / 5;
    background: linear-gradient(135deg, var(--primary) 0%, var(--primary-light) 100%);
    border-radius: var(--radius-lg);
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    color: white;
    text-align: center;
    padding: 40px;
    box-shadow: var(--shadow-lg);
}

.placeholder-icon {
    font-size: 6rem;
    margin-bottom: 20px;
    filter: drop-shadow(0 4px 12px rgba(0, 0, 0, 0.2));
}

.image-placeholder p {
    font-size: 1.4rem;
    font-weight: 700;
    letter-spacing: 2px;
}

.about-heading {
    font-size: 1.8rem;
    color: var(--text-dark);
    margin-bottom: 20px;
    font-weight: 700;
}

.about-text {
    color: var(--text-medium);
    margin-bottom: 16px;
    font-size: 1.02rem;
    line-height: 1.85;
}

.about-features {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 20px;
    margin-top: 36px;
}

.feature-item {
    padding: 24px;
    background: var(--bg-light);
    border-radius: var(--radius-md);
    transition: var(--transition);
}

.feature-item:hover {
    background: white;
    box-shadow: var(--shadow-md);
    transform: translateY(-4px);
}

.feature-icon {
    font-size: 2rem;
    margin-bottom: 12px;
}

.feature-item h4 {
    font-size: 1.1rem;
    color: var(--text-dark);
    margin-bottom: 8px;
    font-weight: 700;
}

.feature-item p {
    font-size: 0.9rem;
    color: var(--text-medium);
}

/* Teachers */
.teachers-section {
    background: var(--bg-light);
}

.teachers-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(340px, 1fr));
    gap: 28px;
}

.teacher-card {
    background: white;
    border-radius: var(--radius-lg);
    padding: 36px 28px;
    box-shadow: var(--shadow-sm);
    transition: var(--transition);
    border: 1px solid var(--border);
}

.teacher-card:hover {
    transform: translateY(-6px);
    box-shadow: var(--shadow-lg);
    border-color: transparent;
}

.teacher-card-single {
    display: flex;
    align-items: flex-start;
    gap: 32px;
    max-width: 800px;
    margin: 0 auto;
}

.teacher-card-single .teacher-avatar {
    width: 180px;
    height: 180px;
    flex-shrink: 0;
}

.teacher-avatar {
    width: 80px;
    height: 80px;
    border-radius: 50%;
    background: linear-gradient(135deg, var(--primary), var(--primary-light));
    display: flex;
    align-items: center;
    justify-content: center;
    margin-bottom: 20px;
    box-shadow: 0 8px 20px rgba(30, 95, 191, 0.25);
    overflow: hidden;
}

.teacher-avatar img {
    width: 100%;
    height: 100%;
    max-width: 100%;
    max-height: 100%;
    object-fit: cover;
}

.avatar-letter {
    font-size: 2rem;
    color: white;
    font-weight: 700;
}

.teacher-name {
    font-size: 1.35rem;
    color: var(--text-dark);
    margin-bottom: 6px;
    font-weight: 700;
}

.teacher-title {
    color: var(--primary);
    font-size: 0.95rem;
    font-weight: 600;
    margin-bottom: 16px;
}

.teacher-desc {
    color: var(--text-medium);
    font-size: 0.95rem;
    line-height: 1.8;
    margin-bottom: 20px;
}

.teacher-tags {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
}

.teacher-tags span {
    padding: 6px 14px;
    background: var(--bg-light);
    color: var(--text-medium);
    font-size: 0.85rem;
    border-radius: 20px;
    font-weight: 500;
    transition: var(--transition);
}

.teacher-tags span:hover {
    background: var(--primary);
    color: white;
}

/* Courses */
.courses-section {
    background: white;
}

.courses-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
    gap: 28px;
    margin-bottom: 48px;
}

.course-card {
    background: white;
    border-radius: var(--radius-lg);
    overflow: hidden;
    box-shadow: var(--shadow-sm);
    transition: var(--transition);
    border: 1px solid var(--border);
    position: relative;
}

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

.course-badge {
    position: absolute;
    top: 20px;
    right: 20px;
    padding: 6px 16px;
    background: var(--secondary);
    color: white;
    font-size: 0.8rem;
    font-weight: 700;
    border-radius: 20px;
    z-index: 1;
    box-shadow: 0 4px 12px rgba(245, 166, 35, 0.3);
}

.course-badge-alt {
    background: var(--accent);
    box-shadow: 0 4px 12px rgba(231, 76, 60, 0.3);
}

.course-header {
    padding: 36px 28px;
    color: white;
}

.course-header-1 {
    background: linear-gradient(135deg, #1e5fbf, #3d7fd9);
}

.course-header-2 {
    background: linear-gradient(135deg, #27ae60, #2ecc71);
}

.course-header-3 {
    background: linear-gradient(135deg, #8e44ad, #9b59b6);
}

.course-title {
    font-size: 1.5rem;
    font-weight: 700;
    margin-bottom: 8px;
}

.course-subtitle {
    font-size: 0.95rem;
    opacity: 0.9;
}

.course-body {
    padding: 28px;
}

.course-outline {
    margin-bottom: 24px;
}

.course-outline li {
    padding: 10px 0;
    color: var(--text-medium);
    font-size: 0.95rem;
    border-bottom: 1px dashed var(--border);
    position: relative;
    padding-left: 20px;
}

.course-outline li::before {
    content: '✓';
    position: absolute;
    left: 0;
    color: var(--primary);
    font-weight: 700;
}

.course-outline li:last-child {
    border-bottom: none;
}

.course-meta {
    display: flex;
    justify-content: space-between;
    padding: 16px;
    background: var(--bg-light);
    border-radius: var(--radius-sm);
    margin-bottom: 20px;
}

.meta-item {
    display: flex;
    flex-direction: column;
    gap: 4px;
}

.meta-label {
    font-size: 0.8rem;
    color: var(--text-light);
}

.meta-value {
    font-size: 0.95rem;
    font-weight: 700;
    color: var(--text-dark);
}

.course-price {
    display: flex;
    align-items: baseline;
    gap: 12px;
}

.price-current {
    font-size: 1.8rem;
    color: var(--accent);
    font-weight: 800;
}

.price-original {
    font-size: 1rem;
    color: var(--text-light);
    text-decoration: line-through;
}

/* Package */
.course-package {
    margin-top: 48px;
}

.package-card {
    background: linear-gradient(135deg, var(--primary) 0%, var(--primary-dark) 100%);
    border-radius: var(--radius-lg);
    padding: 48px;
    color: white;
    display: grid;
    grid-template-columns: 2fr 1fr;
    gap: 40px;
    align-items: center;
    box-shadow: var(--shadow-lg);
}

.package-info h3 {
    font-size: 1.8rem;
    margin-bottom: 12px;
    font-weight: 700;
}

.package-info > p {
    font-size: 1.05rem;
    opacity: 0.9;
    margin-bottom: 24px;
}

.package-benefits {
    display: grid;
    gap: 10px;
}

.package-benefits li {
    font-size: 0.98rem;
    opacity: 0.95;
}

.package-action {
    text-align: center;
}

.package-price {
    margin-bottom: 24px;
}

.package-current {
    display: block;
    font-size: 2.5rem;
    font-weight: 800;
    color: var(--secondary);
    margin-bottom: 8px;
    text-shadow: 0 4px 12px rgba(245, 166, 35, 0.4);
}

.package-original {
    font-size: 1rem;
    opacity: 0.7;
    text-decoration: line-through;
}

.package-card .btn-primary {
    background: var(--secondary);
    color: var(--text-dark);
    box-shadow: 0 6px 20px rgba(245, 166, 35, 0.4);
}

.package-card .btn-primary:hover {
    background: #e8981c;
    box-shadow: 0 10px 28px rgba(245, 166, 35, 0.5);
}

.package-card-alt {
    background: linear-gradient(135deg, #27ae60 0%, #1e8449 100%);
    margin-top: 24px;
}

.package-badge {
    display: inline-block;
    padding: 6px 16px;
    background: rgba(255, 255, 255, 0.2);
    color: white;
    font-size: 0.85rem;
    font-weight: 700;
    border-radius: 20px;
    margin-bottom: 12px;
}

.package-badge-alt {
    background: var(--secondary);
    color: var(--text-dark);
}

/* Contact */
.contact-section {
    background: var(--bg-light);
}

.contact-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
    gap: 24px;
}

.contact-card {
    background: white;
    padding: 40px 28px;
    border-radius: var(--radius-lg);
    text-align: center;
    box-shadow: var(--shadow-sm);
    transition: var(--transition);
    border: 1px solid var(--border);
}

.contact-card:hover {
    transform: translateY(-6px);
    box-shadow: var(--shadow-md);
    border-color: transparent;
}

.contact-icon {
    font-size: 2.5rem;
    margin-bottom: 16px;
}

.contact-card h3 {
    font-size: 1.15rem;
    color: var(--text-dark);
    margin-bottom: 12px;
    font-weight: 700;
}

.contact-card p {
    color: var(--text-medium);
    font-size: 0.98rem;
}

.contact-note {
    font-size: 0.85rem !important;
    color: var(--text-light) !important;
    margin-top: 6px;
}

/* Footer */
.footer {
    background: var(--text-dark);
    color: white;
    padding: 60px 0 24px;
}

.footer-content {
    display: grid;
    grid-template-columns: 1.5fr 1fr 1fr;
    gap: 48px;
    margin-bottom: 40px;
}

.footer-brand .logo {
    color: white;
    margin-bottom: 16px;
}

.footer-brand .logo-icon {
    background: linear-gradient(135deg, var(--secondary), #e8981c);
    box-shadow: 0 4px 12px rgba(245, 166, 35, 0.3);
}

.footer-brand p {
    color: rgba(255, 255, 255, 0.6);
    font-size: 0.95rem;
    line-height: 1.8;
    max-width: 320px;
}

.footer-links h4,
.footer-courses h4 {
    font-size: 1.1rem;
    margin-bottom: 20px;
    font-weight: 700;
}

.footer-links a,
.footer-courses a {
    display: block;
    padding: 6px 0;
    color: rgba(255, 255, 255, 0.6);
    font-size: 0.95rem;
}

.footer-links a:hover,
.footer-courses a:hover {
    color: var(--secondary);
    transform: translateX(4px);
}

.footer-bottom {
    padding-top: 24px;
    border-top: 1px solid rgba(255, 255, 255, 0.1);
    text-align: center;
    color: rgba(255, 255, 255, 0.4);
    font-size: 0.9rem;
}

/* Back to top */
.back-to-top {
    position: fixed;
    bottom: 32px;
    right: 32px;
    width: 48px;
    height: 48px;
    background: var(--primary);
    color: white;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.4rem;
    font-weight: 700;
    box-shadow: var(--shadow-lg);
    opacity: 0;
    visibility: hidden;
    transform: translateY(20px);
    transition: var(--transition);
    z-index: 999;
}

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

.back-to-top:hover {
    background: var(--primary-dark);
    transform: translateY(-4px);
}

/* Animations */
.fade-in {
    opacity: 0;
    transform: translateY(30px);
    transition: opacity 0.8s ease-out, transform 0.8s ease-out;
}

.fade-in.visible {
    opacity: 1;
    transform: translateY(0);
}

/* Responsive */
@media (max-width: 992px) {
    .about-grid {
        grid-template-columns: 1fr;
        gap: 40px;
    }

    .about-image {
        max-width: 400px;
        margin: 0 auto;
    }

    .package-card {
        grid-template-columns: 1fr;
        padding: 36px 28px;
    }

    .footer-content {
        grid-template-columns: 1fr 1fr;
    }
}

@media (max-width: 768px) {
    .nav-menu {
        position: fixed;
        top: 72px;
        left: 0;
        right: 0;
        background: white;
        flex-direction: column;
        padding: 20px;
        gap: 4px;
        box-shadow: var(--shadow-md);
        transform: translateY(-10px);
        opacity: 0;
        visibility: hidden;
        transition: var(--transition);
    }

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

    .nav-link {
        width: 100%;
        padding: 14px 20px;
    }

    .nav-toggle {
        display: flex;
    }

    .nav-toggle.active span:nth-child(1) {
        transform: rotate(45deg) translate(6px, 6px);
    }

    .nav-toggle.active span:nth-child(2) {
        opacity: 0;
    }

    .nav-toggle.active span:nth-child(3) {
        transform: rotate(-45deg) translate(6px, -6px);
    }

    .hero {
        padding: 130px 0 70px;
    }

    .hero-stats {
        grid-template-columns: repeat(2, 1fr);
    }

    .section {
        padding: 70px 0;
    }

    .about-features {
        grid-template-columns: 1fr;
    }

    .footer-content {
        grid-template-columns: 1fr;
        gap: 32px;
    }

    .back-to-top {
        bottom: 20px;
        right: 20px;
        width: 42px;
        height: 42px;
    }
}

@media (max-width: 480px) {
    .container {
        padding: 0 16px;
    }

    .hero-stats {
        grid-template-columns: 1fr 1fr;
        gap: 12px;
    }

    .stat-item {
        padding: 20px 12px;
    }

    .stat-number {
        font-size: 1.6rem;
    }

    .hero-actions {
        flex-direction: column;
    }

    .hero-actions .btn {
        width: 100%;
    }

    .teachers-grid,
    .courses-grid,
    .contact-grid {
        grid-template-columns: 1fr;
    }

    .package-card {
        padding: 28px 20px;
    }

    .package-current {
        font-size: 2rem;
    }
}