/* ===================================
   主样式文件 - 人工智能课程网站
   设计风格：简洁、专业、有质感
   =================================== */

:root {
    --primary: #2c5f7f;
    --accent: #d4a574;
    --dark: #1a1a1f;
    --light: #f5f5f3;
    --gray: #8a8a8a;
    --border: rgba(44, 95, 127, 0.15);
    --shadow: rgba(44, 95, 127, 0.1);
}

/* 全局样式 */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: 'Noto Sans SC', -apple-system, sans-serif;
    background: var(--light);
    color: var(--dark);
    line-height: 1.7;
    overflow-x: hidden;
}

body::before {
    content: '';
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-image: url("data:image/svg+xml,%3Csvg viewBox='0 0 400 400' xmlns='http://www.w3.org/2000/svg'%3E%3Cfilter id='noiseFilter'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='0.9' numOctaves='3' stitchTiles='stitch'/%3E%3C/filter%3E%3Crect width='100%25' height='100%25' filter='url(%23noiseFilter)'/%3E%3C/svg%3E");
    opacity: 0.03;
    pointer-events: none;
    z-index: 1000;
}

/* 链接样式 */
a {
    color: var(--primary);
    text-decoration: none;
    transition: all 0.3s ease;
}

a:hover {
    color: var(--accent);
}

/* 容器 */
.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 60px;
}

.container-narrow {
    max-width: 900px;
    margin: 0 auto;
    padding: 0 60px;
}

/* 导航栏 */
.navbar {
    background: #fff;
    border-bottom: 1px solid var(--border);
    position: sticky;
    top: 0;
    z-index: 100;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.05);
}

.navbar-content {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 20px 60px;
    max-width: 1400px;
    margin: 0 auto;
}

.navbar-brand {
    display: flex;
    align-items: center;
    gap: 15px;
    text-decoration: none;
    color: var(--dark);
}

.navbar-brand-text {
    font-family: 'Crimson Pro', serif;
    font-size: 1.5rem;
    font-weight: 600;
}

.navbar-tag {
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.7rem;
    color: var(--gray);
    padding: 4px 10px;
    background: var(--light);
    border-radius: 3px;
}

.navbar-nav {
    display: flex;
    gap: 30px;
}

.navbar-link {
    font-size: 0.95rem;
    color: var(--dark);
    text-decoration: none;
    transition: all 0.3s ease;
    position: relative;
}

.navbar-link:hover {
    color: var(--primary);
}

.navbar-link::after {
    content: '';
    position: absolute;
    bottom: -5px;
    left: 0;
    width: 0;
    height: 2px;
    background: var(--primary);
    transition: width 0.3s ease;
}

.navbar-link:hover::after {
    width: 100%;
}

/* 页脚 */
.footer {
    background: var(--dark);
    color: rgba(255, 255, 255, 0.7);
    padding: 60px 0;
    margin-top: 100px;
}

.footer-content {
    max-width: 1400px;
    margin: 0 auto;
    padding: 0 60px;
}

.footer-section {
    margin-bottom: 40px;
}

.footer-title {
    font-size: 1.1rem;
    font-weight: 500;
    color: #fff;
    margin-bottom: 20px;
}

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

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

.footer-links a {
    color: rgba(255, 255, 255, 0.6);
    text-decoration: none;
    transition: color 0.3s ease;
}

.footer-links a:hover {
    color: var(--accent);
}

.footer-bottom {
    text-align: center;
    padding-top: 40px;
    border-top: 1px solid rgba(255, 255, 255, 0.1);
    font-size: 0.9rem;
    color: rgba(255, 255, 255, 0.5);
}

/* 按钮样式 */
.btn {
    display: inline-flex;
    align-items: center;
    gap: 10px;
    padding: 12px 28px;
    border-radius: 4px;
    font-size: 0.95rem;
    font-weight: 500;
    text-decoration: none;
    transition: all 0.3s ease;
    cursor: pointer;
    border: none;
}

.btn-primary {
    background: var(--primary);
    color: #fff;
}

.btn-primary:hover {
    background: var(--accent);
    color: #fff;
}

.btn-outline {
    background: transparent;
    color: var(--primary);
    border: 1px solid var(--primary);
}

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

.btn-link {
    background: transparent;
    color: var(--primary);
    padding: 8px 0;
}

.btn-link:hover {
    color: var(--accent);
    gap: 13px;
}

/* 标题样式 */
h1, h2, h3, h4 {
    font-family: 'Crimson Pro', serif;
    font-weight: 400;
    line-height: 1.3;
}

h1 {
    font-size: clamp(2.5rem, 5vw, 4rem);
    letter-spacing: -0.02em;
}

h2 {
    font-size: clamp(2rem, 4vw, 2.5rem);
    margin-bottom: 30px;
}

h3 {
    font-size: 1.5rem;
    margin-bottom: 20px;
}

/* 标签 */
.tag {
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.75rem;
    color: var(--gray);
    letter-spacing: 0.2em;
    text-transform: uppercase;
    padding: 6px 12px;
    background: var(--light);
    border-radius: 3px;
}

/* 分隔线 */
.divider {
    width: 60px;
    height: 2px;
    background: var(--accent);
    margin: 40px 0;
}

/* 章节样式 */
.section {
    padding: 80px 0;
}

.section-title {
    font-size: 2rem;
    margin-bottom: 50px;
    display: flex;
    align-items: center;
    gap: 20px;
}

.section-title::before {
    content: '';
    width: 40px;
    height: 1px;
    background: var(--accent);
}

/* 卡片样式 */
.card {
    background: #fff;
    border: 1px solid var(--border);
    border-radius: 8px;
    padding: 30px;
    transition: all 0.3s ease;
}

.card:hover {
    border-color: var(--primary);
    box-shadow: 0 8px 30px rgba(44, 95, 127, 0.15);
}

/* 网格布局 */
.grid-2 {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 30px;
}

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

.grid-4 {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 30px;
}

/* 动画 */
.fade-in {
    opacity: 0;
    transform: translateY(20px);
    animation: fadeIn 0.8s ease forwards;
}

@keyframes fadeIn {
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.delay-1 { animation-delay: 0.1s; }
.delay-2 { animation-delay: 0.2s; }
.delay-3 { animation-delay: 0.3s; }
.delay-4 { animation-delay: 0.4s; }
.delay-5 { animation-delay: 0.5s; }
.delay-6 { animation-delay: 0.6s; }

/* 响应式 */
@media (max-width: 1024px) {
    .container,
    .container-narrow {
        padding: 0 40px;
    }

    .navbar-content {
        padding: 15px 40px;
    }

    .navbar-nav {
        gap: 20px;
    }

    .grid-4 {
        grid-template-columns: repeat(3, 1fr);
    }
}

@media (max-width: 768px) {
    .container,
    .container-narrow {
        padding: 0 25px;
    }

    .navbar-content {
        padding: 15px 25px;
        flex-direction: column;
        gap: 15px;
    }

    .navbar-nav {
        flex-wrap: wrap;
        justify-content: center;
        gap: 15px;
    }

    .grid-2,
    .grid-3,
    .grid-4 {
        grid-template-columns: 1fr;
    }
}

/* 加载Google Fonts */
@import url('https://fonts.googleapis.com/css2?family=Crimson+Pro:wght@300;400;600;700&family=JetBrains+Mono:wght@300;400;500&family=Noto+Sans+SC:wght@300;400;500;700&display=swap');

/* Hero Section */
.hero {
    text-align: center;
    padding: 100px 0 80px;
}

.hero-tag {
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.75rem;
    color: var(--gray);
    letter-spacing: 0.2em;
    text-transform: uppercase;
    margin-bottom: 20px;
    display: block;
}

.hero-title {
    font-size: clamp(3rem, 8vw, 5rem);
    font-weight: 300;
    color: var(--dark);
    margin-bottom: 20px;
    letter-spacing: -0.02em;
    line-height: 1.1;
}

.hero-subtitle {
    font-size: 1.5rem;
    color: var(--gray);
    font-weight: 300;
    margin-bottom: 20px;
}

/* 课程介绍 */
.course-intro {
    max-width: 800px;
    margin: 0 auto;
    text-align: center;
    font-size: 1.1rem;
    line-height: 1.8;
    color: #3a3a3a;
}

/* CTA按钮 */
.cta-button {
    display: inline-block;
    padding: 14px 32px;
    background: var(--primary);
    color: #fff;
    text-decoration: none;
    border-radius: 4px;
    font-size: 1rem;
    font-weight: 500;
    transition: all 0.3s ease;
}

.cta-button:hover {
    background: var(--accent);
    transform: translateY(-2px);
    box-shadow: 0 8px 20px rgba(212, 165, 116, 0.3);
}