/* ========================================
   章节页面现代风格样式表
   ======================================== */

/* CSS变量 */
:root {
    --primary: #6366f1;
    --primary-light: #818cf8;
    --primary-dark: #4f46e5;
    --secondary: #ec4899;
    --accent: #06b6d4;
    --dark: #0f172a;
    --dark-light: #1e293b;
    --gray: #64748b;
    --gray-light: #94a3b8;
    --white: #ffffff;
    --glass-bg: rgba(255, 255, 255, 0.08);
    --glass-border: rgba(255, 255, 255, 0.1);
    --shadow: 0 8px 32px rgba(0, 0, 0, 0.3);
    --shadow-light: 0 4px 16px rgba(0, 0, 0, 0.1);
    --radius: 16px;
    --radius-sm: 8px;
    --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

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

body {
    font-family: 'Noto Sans SC', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    background: linear-gradient(135deg, #0f172a 0%, #1e1b4b 50%, #312e81 100%);
    min-height: 100vh;
    color: var(--white);
    line-height: 1.6;
    overflow-x: hidden;
}

::-webkit-scrollbar { width: 8px; }
::-webkit-scrollbar-track { background: var(--dark); }
::-webkit-scrollbar-thumb { background: var(--primary); border-radius: 4px; }
::-webkit-scrollbar-thumb:hover { background: var(--primary-light); }

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

/* ========================================
   头部导航
   ======================================== */
.header {
    background: var(--glass-bg);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    border-bottom: 1px solid var(--glass-border);
    position: sticky;
    top: 0;
    z-index: 1000;
    padding: 16px 0;
}

.header .container {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 24px;
}

.logo { flex-shrink: 0; }
.logo img { height: 42px; width: auto; filter: brightness(1.2); }

.nav ul {
    display: flex;
    list-style: none;
    gap: 8px;
}

.nav ul li a {
    display: block;
    padding: 10px 20px;
    color: var(--gray-light);
    text-decoration: none;
    font-size: 15px;
    font-weight: 500;
    border-radius: var(--radius-sm);
    transition: var(--transition);
    position: relative;
}

.nav ul li a:hover,
.nav ul li a.active {
    color: var(--white);
    background: var(--glass-bg);
}

.nav ul li a.active::after {
    content: '';
    position: absolute;
    bottom: 4px;
    left: 20px;
    right: 20px;
    height: 2px;
    background: linear-gradient(90deg, var(--primary), var(--secondary));
    border-radius: 2px;
}

.search {
    display: flex;
    align-items: center;
    background: var(--glass-bg);
    border: 1px solid var(--glass-border);
    border-radius: 50px;
    padding: 4px;
    transition: var(--transition);
    max-width: 300px;
    flex: 1;
}

.search.focused {
    border-color: var(--primary-light);
    box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.2);
}

.search input {
    flex: 1;
    background: transparent;
    border: none;
    padding: 8px 16px;
    color: var(--white);
    font-size: 14px;
    outline: none;
}

.search input::placeholder { color: var(--gray); }

.search button {
    background: linear-gradient(135deg, var(--primary), var(--primary-dark));
    border: none;
    width: 36px;
    height: 36px;
    border-radius: 50%;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    color: var(--white);
    transition: var(--transition);
}

.search button:hover {
    transform: scale(1.1);
    box-shadow: 0 4px 12px rgba(99, 102, 241, 0.4);
}

.user {
    display: flex;
    align-items: center;
    gap: 8px;
    color: var(--gray-light);
    font-size: 14px;
}

.user img {
    width: 36px;
    height: 36px;
    border-radius: 50%;
    border: 2px solid var(--glass-border);
}

/* ========================================
   章节页面头部
   ======================================== */
.chapter-hero {
    padding: 60px 0 40px;
    text-align: center;
    position: relative;
    overflow: hidden;
}

.chapter-hero::before {
    content: '';
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    width: 500px;
    height: 500px;
    background: radial-gradient(circle, rgba(99, 102, 241, 0.2) 0%, transparent 70%);
    pointer-events: none;
}

.chapter-hero .container {
    position: relative;
    z-index: 1;
}

.chapter-hero h1 {
    font-size: 40px;
    font-weight: 700;
    background: linear-gradient(135deg, var(--white) 0%, var(--primary-light) 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    margin-bottom: 20px;
}

.chapter-nav {
    display: flex;
    justify-content: center;
    gap: 12px;
    flex-wrap: wrap;
}

.chapter-nav a {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    padding: 10px 20px;
    background: var(--glass-bg);
    border: 1px solid var(--glass-border);
    border-radius: 50px;
    color: var(--gray-light);
    text-decoration: none;
    font-size: 14px;
    transition: var(--transition);
}

.chapter-nav a:hover {
    color: var(--white);
    border-color: var(--primary-light);
    background: rgba(99, 102, 241, 0.15);
    transform: translateY(-2px);
}

/* ========================================
   章节内容区域
   ======================================== */
.chapter-content {
    padding: 0 0 60px;
}

.section-group {
    margin-bottom: 32px;
    background: var(--glass-bg);
    backdrop-filter: blur(10px);
    -webkit-backdrop-filter: blur(10px);
    border: 1px solid var(--glass-border);
    border-radius: var(--radius);
    padding: 28px 32px;
    transition: var(--transition);
}

.section-group:hover {
    border-color: rgba(99, 102, 241, 0.3);
    box-shadow: var(--shadow-light);
}

.section-group h3 {
    font-size: 18px;
    font-weight: 600;
    margin-bottom: 16px;
    padding-bottom: 12px;
    border-bottom: 1px solid var(--glass-border);
    color: var(--white);
    display: flex;
    align-items: center;
    gap: 10px;
}

.section-group h3::before {
    content: '';
    width: 4px;
    height: 20px;
    background: linear-gradient(180deg, var(--primary), var(--secondary));
    border-radius: 2px;
    flex-shrink: 0;
}

.section-group ul {
    list-style: none;
    display: flex;
    flex-wrap: wrap;
    gap: 10px;
}

.section-group ul li {
    margin: 0;
}

.section-group ul li a {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    padding: 8px 16px;
    background: rgba(255, 255, 255, 0.05);
    border: 1px solid rgba(255, 255, 255, 0.08);
    border-radius: var(--radius-sm);
    color: var(--gray-light);
    text-decoration: none;
    font-size: 14px;
    transition: var(--transition);
}

.section-group ul li a:hover {
    color: var(--white);
    background: rgba(99, 102, 241, 0.2);
    border-color: var(--primary-light);
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(99, 102, 241, 0.2);
}

.section-group ul:empty {
    display: none;
}

.section-group:has(ul:empty) h3 {
    margin-bottom: 0;
    padding-bottom: 0;
    border-bottom: none;
}

.section-group .no-link {
    display: inline-flex;
    align-items: center;
    padding: 8px 16px;
    background: rgba(255, 255, 255, 0.03);
    border: 1px solid rgba(255, 255, 255, 0.05);
    border-radius: var(--radius-sm);
    color: var(--gray);
    font-size: 14px;
}

/* 项目实战和实训作业特殊样式 */
.section-group.practice h3 {
    background: linear-gradient(135deg, var(--primary), var(--accent));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.section-group.practice h3::before {
    background: linear-gradient(180deg, var(--accent), var(--primary));
}

.section-group.training h3 {
    background: linear-gradient(135deg, var(--secondary), var(--primary));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.section-group.training h3::before {
    background: linear-gradient(180deg, var(--secondary), var(--primary));
}

.section-group.practice ul li a,
.section-group.training ul li a {
    background: rgba(99, 102, 241, 0.1);
    border-color: rgba(99, 102, 241, 0.2);
    padding: 10px 18px;
}

.section-group.practice ul li a:hover,
.section-group.training ul li a:hover {
    background: rgba(99, 102, 241, 0.25);
}

/* ========================================
   页脚
   ======================================== */
.footer {
    background: var(--glass-bg);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    border-top: 1px solid var(--glass-border);
    padding: 40px 0;
}

.footer .container {
    text-align: center;
}

.footer .container p {
    color: var(--gray);
    font-size: 13px;
}

.footer .container p + p {
    margin-top: 4px;
    color: var(--gray-light);
    font-size: 12px;
}

/* ========================================
   响应式
   ======================================== */
@media (max-width: 768px) {
    .header .container {
        flex-wrap: wrap;
    }
    .nav { order: 3; width: 100%; }
    .nav ul { justify-content: center; }
    .search { max-width: 200px; }
    .chapter-hero h1 { font-size: 28px; }
    .section-group { padding: 20px; }
    .section-group ul { flex-direction: column; }
}