/* ========================================
   全局重置 & 变量
   ======================================== */
:root {
    --primary: #6366f1;
    --primary-dark: #4f46e5;
    --primary-light: #a5b4fc;
    --secondary: #f59e0b;
    --accent: #06b6d4;
    --bg-dark: #0f172a;
    --bg-section: #f8fafc;
    --bg-card: #ffffff;
    --text-dark: #1e293b;
    --text-muted: #64748b;
    --text-light: #94a3b8;
    --shadow-sm: 0 4px 12px rgba(0,0,0,0.06);
    --shadow-md: 0 8px 30px rgba(0,0,0,0.1);
    --shadow-lg: 0 20px 60px rgba(0,0,0,0.15);
    --radius-sm: 8px;
    --radius-md: 16px;
    --radius-lg: 24px;
    --font-sans: 'Noto Sans SC', -apple-system, BlinkMacSystemFont, sans-serif;
    --font-display: 'Playfair Display', serif;
    --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

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

html {
    scroll-behavior: smooth;
    font-size: 16px;
}

body {
    font-family: var(--font-sans);
    color: var(--text-dark);
    background: #fff;
    line-height: 1.6;
    overflow-x: hidden;
}

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

ul {
    list-style: none;
}

img, .img-placeholder {
    max-width: 100%;
    display: block;
}

.container {
    width: 100%;
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
}

/* ========================================
   按钮
   ======================================== */
.btn {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 14px 32px;
    border-radius: 50px;
    font-weight: 600;
    font-size: 1rem;
    border: none;
    cursor: pointer;
    transition: var(--transition);
    position: relative;
    overflow: hidden;
}

.btn-primary {
    background: linear-gradient(135deg, var(--primary), var(--primary-dark));
    color: #fff;
    box-shadow: 0 4px 15px rgba(99, 102, 241, 0.4);
}

.btn-primary:hover {
    transform: translateY(-3px);
    box-shadow: 0 8px 25px rgba(99, 102, 241, 0.5);
}

.btn-secondary {
    background: rgba(255,255,255,0.15);
    backdrop-filter: blur(10px);
    color: #fff;
    border: 1px solid rgba(255,255,255,0.3);
}

.btn-secondary:hover {
    background: rgba(255,255,255,0.25);
    transform: translateY(-3px);
}

.btn-outline {
    background: transparent;
    color: var(--primary);
    border: 2px solid var(--primary);
    padding: 10px 24px;
    font-size: 0.9rem;
}

.btn-outline:hover {
    background: var(--primary);
    color: #fff;
    transform: translateY(-2px);
}

.btn-full {
    width: 100%;
    justify-content: center;
}

/* ========================================
   导航栏
   ======================================== */
.header {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    z-index: 1000;
    padding: 16px 0;
    transition: var(--transition);
    background: transparent;
}

.header.scrolled {
    background: rgba(15, 23, 42, 0.92);
    backdrop-filter: blur(20px);
    padding: 10px 0;
    box-shadow: 0 4px 30px rgba(0,0,0,0.1);
}

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

.logo {
    font-size: 1.5rem;
    font-weight: 700;
    color: #fff;
    display: flex;
    align-items: center;
    gap: 8px;
}

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

.nav-list {
    display: flex;
    gap: 32px;
}

.nav-link {
    color: rgba(255,255,255,0.8);
    font-weight: 500;
    font-size: 0.95rem;
    position: relative;
    padding-bottom: 4px;
}

.nav-link::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 0;
    width: 0;
    height: 2px;
    background: var(--secondary);
    transition: var(--transition);
}

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

.nav-link:hover::after,
.nav-link.active::after {
    width: 100%;
}

.hamburger {
    display: none;
    flex-direction: column;
    gap: 5px;
    cursor: pointer;
    z-index: 1001;
}

.hamburger .bar {
    width: 28px;
    height: 3px;
    background: #fff;
    border-radius: 2px;
    transition: var(--transition);
}

.hamburger.active .bar:nth-child(1) {
    transform: rotate(45deg) translate(5px, 6px);
}

.hamburger.active .bar:nth-child(2) {
    opacity: 0;
}

.hamburger.active .bar:nth-child(3) {
    transform: rotate(-45deg) translate(5px, -6px);
}

/* ========================================
   Hero
   ======================================== */
.hero {
    min-height: 100vh;
    background: linear-gradient(135deg, #0f172a 0%, #1e293b 50%, #0f172a 100%);
    display: flex;
    align-items: center;
    position: relative;
    overflow: hidden;
}

.hero-overlay {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: radial-gradient(circle at 30% 50%, rgba(99, 102, 241, 0.15) 0%, transparent 60%),
                radial-gradient(circle at 70% 80%, rgba(6, 182, 212, 0.1) 0%, transparent 50%);
    pointer-events: none;
}

.hero-content {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 60px;
    align-items: center;
    position: relative;
    z-index: 1;
    padding: 120px 0 80px;
}

.hero-text {
    color: #fff;
}

.hero-title {
    font-size: 3.2rem;
    font-weight: 900;
    line-height: 1.2;
    margin-bottom: 20px;
    background: linear-gradient(135deg, #fff 0%, #a5b4fc 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.hero-subtitle {
    font-size: 1.1rem;
    color: rgba(255,255,255,0.7);
    margin-bottom: 36px;
    max-width: 480px;
}

.hero-buttons {
    display: flex;
    gap: 16px;
    margin-bottom: 48px;
    flex-wrap: wrap;
}

.hero-stats {
    display: flex;
    gap: 40px;
    flex-wrap: wrap;
}

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

.stat-number {
    font-size: 2.2rem;
    font-weight: 900;
    color: var(--secondary);
    font-family: var(--font-display);
}

.stat-item p {
    color: rgba(255,255,255,0.6);
    font-size: 0.85rem;
    margin-top: 4px;
}

.hero-image .img-placeholder {
    width: 100%;
    aspect-ratio: 1 / 1;
    max-width: 450px;
    margin: 0 auto;
    background: linear-gradient(135deg, rgba(99,102,241,0.2), rgba(6,182,212,0.1));
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 6rem;
    color: rgba(255,255,255,0.2);
    border: 2px solid rgba(255,255,255,0.05);
    position: relative;
}

.hero-image .img-placeholder span {
    position: absolute;
    font-size: 8rem;
    animation: float 6s ease-in-out infinite;
}

@keyframes float {
    0%, 100% { transform: translateY(0) scale(1); }
    50% { transform: translateY(-20px) scale(1.05); }
}

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

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

.section-header.left-align {
    text-align: left;
}

.section-tag {
    display: inline-block;
    background: linear-gradient(135deg, var(--primary-light), var(--primary));
    color: #fff;
    padding: 6px 18px;
    border-radius: 50px;
    font-size: 0.85rem;
    font-weight: 600;
    letter-spacing: 1px;
    margin-bottom: 16px;
}

.section-title {
    font-size: 2.4rem;
    font-weight: 800;
    margin-bottom: 12px;
    color: var(--text-dark);
}

.section-desc {
    color: var(--text-muted);
    font-size: 1.05rem;
    max-width: 540px;
    margin: 0 auto;
}

.section-header.left-align .section-desc {
    margin: 0;
}

/* ========================================
   关于
   ======================================== */
.about {
    background: var(--bg-section);
}

.about-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 24px;
}

.about-card {
    background: var(--bg-card);
    padding: 32px 24px;
    border-radius: var(--radius-md);
    text-align: center;
    box-shadow: var(--shadow-sm);
    transition: var(--transition);
    border: 1px solid rgba(0,0,0,0.04);
}

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

.about-icon {
    width: 60px;
    height: 60px;
    border-radius: 50%;
    background: linear-gradient(135deg, var(--primary-light), var(--primary));
    display: flex;
    align-items: center;
    justify-content: center;
    margin: 0 auto 20px;
    color: #fff;
    font-size: 1.5rem;
}

.about-card h3 {
    font-size: 1.2rem;
    margin-bottom: 10px;
}

.about-card p {
    color: var(--text-muted);
    font-size: 0.95rem;
}

/* ========================================
   课程
   ======================================== */
.courses {
    background: #fff;
}

.course-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 24px;
}

.course-card {
    background: var(--bg-card);
    border-radius: var(--radius-md);
    overflow: hidden;
    box-shadow: var(--shadow-sm);
    transition: var(--transition);
    border: 1px solid rgba(0,0,0,0.04);
    display: flex;
    flex-direction: column;
}

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

.course-image {
    background: linear-gradient(135deg, #e0e7ff, #c7d2fe);
    padding: 32px 20px;
    text-align: center;
    font-size: 3rem;
    color: var(--primary);
}

.course-body {
    padding: 24px;
    flex: 1;
    display: flex;
    flex-direction: column;
}

.course-title {
    font-size: 1.15rem;
    margin-bottom: 4px;
}

.course-age {
    color: var(--primary);
    font-weight: 600;
    font-size: 0.85rem;
    margin-bottom: 12px;
}

.course-desc {
    color: var(--text-muted);
    font-size: 0.9rem;
    margin-bottom: 16px;
    flex: 1;
}

.course-features {
    margin-bottom: 20px;
}

.course-features li {
    font-size: 0.85rem;
    color: var(--text-muted);
    margin-bottom: 6px;
    display: flex;
    align-items: center;
    gap: 8px;
}

.course-features li i {
    color: var(--primary);
}

/* ========================================
   名师
   ======================================== */
.teachers {
    background: var(--bg-section);
}

.teacher-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 30px;
}

.teacher-card {
    background: var(--bg-card);
    padding: 36px 28px;
    border-radius: var(--radius-md);
    text-align: center;
    box-shadow: var(--shadow-sm);
    transition: var(--transition);
    border: 1px solid rgba(0,0,0,0.04);
}

.teacher-card:hover {
    transform: translateY(-6px);
    box-shadow: var(--shadow-md);
}

.teacher-avatar {
    font-size: 4rem;
    color: var(--primary-light);
    margin-bottom: 16px;
}

.teacher-name {
    font-size: 1.3rem;
    margin-bottom: 4px;
}

.teacher-title {
    color: var(--primary);
    font-weight: 500;
    font-size: 0.9rem;
    margin-bottom: 14px;
}

.teacher-bio {
    color: var(--text-muted);
    font-size: 0.9rem;
    margin-bottom: 16px;
}

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

.teacher-tags span {
    background: #eef2ff;
    color: var(--primary);
    padding: 4px 14px;
    border-radius: 50px;
    font-size: 0.8rem;
    font-weight: 500;
}

/* ========================================
   学员评价
   ======================================== */
.testimonials {
    background: #fff;
}

.testimonial-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 24px;
}

.testimonial-card {
    background: var(--bg-section);
    padding: 32px 28px;
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-sm);
    transition: var(--transition);
}

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

.testimonial-stars {
    color: var(--secondary);
    margin-bottom: 16px;
    font-size: 0.95rem;
}

.testimonial-text {
    color: var(--text-dark);
    font-size: 0.95rem;
    line-height: 1.7;
    margin-bottom: 20px;
    font-style: italic;
}

.testimonial-author {
    display: flex;
    align-items: center;
    gap: 12px;
}

.author-avatar {
    width: 44px;
    height: 44px;
    border-radius: 50%;
    background: linear-gradient(135deg, var(--primary-light), var(--primary));
    display: flex;
    align-items: center;
    justify-content: center;
    color: #fff;
    font-size: 1.2rem;
}

.testimonial-author h4 {
    font-size: 1rem;
    margin-bottom: 2px;
}

.testimonial-author span {
    font-size: 0.8rem;
    color: var(--text-muted);
}

/* ========================================
   联系我们
   ======================================== */
.contact {
    background: var(--bg-section);
}

.contact-wrapper {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 48px;
    align-items: start;
}

.info-items {
    display: flex;
    flex-direction: column;
    gap: 24px;
    margin-top: 32px;
}

.info-item {
    display: flex;
    gap: 16px;
    align-items: flex-start;
}

.info-item i {
    font-size: 1.4rem;
    color: var(--primary);
    margin-top: 4px;
    width: 28px;
}

.info-item h4 {
    font-size: 1rem;
    margin-bottom: 2px;
}

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

/* 表单 */
.contact-form {
    background: var(--bg-card);
    padding: 36px 32px;
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-sm);
}

.form-group {
    margin-bottom: 18px;
    position: relative;
}

.form-group input,
.form-group select,
.form-group textarea {
    width: 100%;
    padding: 14px 16px;
    border: 2px solid #e2e8f0;
    border-radius: var(--radius-sm);
    font-family: var(--font-sans);
    font-size: 0.95rem;
    transition: var(--transition);
    background: #f8fafc;
    outline: none;
}

.form-group input:focus,
.form-group select:focus,
.form-group textarea:focus {
    border-color: var(--primary);
    background: #fff;
    box-shadow: 0 0 0 4px rgba(99, 102, 241, 0.1);
}

.form-group input.error,
.form-group select.error,
.form-group textarea.error {
    border-color: #ef4444;
}

.error-msg {
    color: #ef4444;
    font-size: 0.8rem;
    margin-top: 4px;
    display: block;
    min-height: 18px;
}

.form-success {
    display: none;
    text-align: center;
    padding: 40px 20px;
}

.form-success i {
    font-size: 4rem;
    color: #10b981;
    margin-bottom: 16px;
}

.form-success h3 {
    font-size: 1.5rem;
    margin-bottom: 8px;
}

.form-success p {
    color: var(--text-muted);
}

/* ========================================
   页脚
   ======================================== */
.footer {
    background: var(--bg-dark);
    color: rgba(255,255,255,0.8);
    padding: 60px 0 0;
}

.footer-content {
    display: grid;
    grid-template-columns: 2fr 1fr 1fr 1.5fr;
    gap: 40px;
    padding-bottom: 40px;
    border-bottom: 1px solid rgba(255,255,255,0.08);
}

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

.footer-brand p {
    font-size: 0.9rem;
    margin-bottom: 20px;
    color: rgba(255,255,255,0.6);
}

.social-links {
    display: flex;
    gap: 12px;
}

.social-links a {
    width: 40px;
    height: 40px;
    border-radius: 50%;
    background: rgba(255,255,255,0.08);
    display: flex;
    align-items: center;
    justify-content: center;
    color: rgba(255,255,255,0.6);
    transition: var(--transition);
}

.social-links a:hover {
    background: var(--primary);
    color: #fff;
    transform: translateY(-3px);
}

.footer-links h4 {
    color: #fff;
    margin-bottom: 20px;
    font-size: 1rem;
}

.footer-links ul li {
    margin-bottom: 10px;
}

.footer-links ul li a {
    color: rgba(255,255,255,0.6);
    font-size: 0.9rem;
}

.footer-links ul li a:hover {
    color: var(--secondary);
    padding-left: 4px;
}

.footer-newsletter h4 {
    color: #fff;
    margin-bottom: 12px;
}

.footer-newsletter p {
    font-size: 0.85rem;
    color: rgba(255,255,255,0.5);
    margin-bottom: 16px;
}

.newsletter-form {
    display: flex;
    gap: 0;
    border-radius: 50px;
    overflow: hidden;
    border: 1px solid rgba(255,255,255,0.15);
}

.newsletter-form input {
    flex: 1;
    padding: 12px 16px;
    border: none;
    background: rgba(255,255,255,0.05);
    color: #fff;
    outline: none;
    font-size: 0.9rem;
}

.newsletter-form input::placeholder {
    color: rgba(255,255,255,0.4);
}

.newsletter-form button {
    padding: 12px 20px;
    background: var(--primary);
    color: #fff;
    border: none;
    cursor: pointer;
    transition: var(--transition);
}

.newsletter-form button:hover {
    background: var(--primary-dark);
}

.footer-bottom {
    text-align: center;
    padding: 24px 0;
    font-size: 0.85rem;
    color: rgba(255,255,255,0.4);
}

/* ========================================
   响应式设计
   ======================================== */
@media (max-width: 1024px) {
    .hero-title { font-size: 2.6rem; }
    .about-grid { grid-template-columns: repeat(2, 1fr); }
    .course-grid { grid-template-columns: repeat(2, 1fr); }
    .footer-content { grid-template-columns: 1fr 1fr; }
}

@media (max-width: 768px) {
    .nav-list {
        position: fixed;
        top: 0;
        right: -100%;
        width: 280px;
        height: 100vh;
        background: rgba(15, 23, 42, 0.98);
        backdrop-filter: blur(20px);
        flex-direction: column;
        padding: 80px 32px 32px;
        gap: 24px;
        transition: var(--transition);
        box-shadow: -10px 0 30px rgba(0,0,0,0.3);
    }

    .nav-list.active {
        right: 0;
    }

    .hamburger {
        display: flex;
    }

    .hero-content {
        grid-template-columns: 1fr;
        text-align: center;
        gap: 40px;
        padding-top: 100px;
    }

    .hero-title { font-size: 2.2rem; }
    .hero-subtitle { max-width: 100%; }
    .hero-buttons { justify-content: center; }
    .hero-stats { justify-content: center; }
    .hero-image .img-placeholder { max-width: 280px; }

    .section { padding: 60px 0; }
    .section-title { font-size: 1.8rem; }

    .about-grid { grid-template-columns: 1fr; }
    .course-grid { grid-template-columns: 1fr; }
    .teacher-grid { grid-template-columns: 1fr; }
    .testimonial-grid { grid-template-columns: 1fr; }
    .contact-wrapper { grid-template-columns: 1fr; }

    .footer-content { grid-template-columns: 1fr; text-align: center; }
    .social-links { justify-content: center; }
    .newsletter-form { max-width: 320px; margin: 0 auto; }
}

@media (max-width: 480px) {
    .hero-title { font-size: 1.8rem; }
    .hero-stats { gap: 20px; }
    .stat-number { font-size: 1.6rem; }
    .contact-form { padding: 24px 16px; }
}