/* ========================================
   CSS Variables & Reset
======================================== */
:root {
    /* Primary Colors - GitHub Blue Family */
    --primary: #2D7FF9;
    --primary-dark: #1B6AD3;
    --primary-darker: #0F4FAA;
    --primary-light: #5BA0FC;
    --primary-lighter: #E8F1FE;

    /* Accent Colors */
    --accent-green: #00C9A7;
    --accent-orange: #FF8C42;
    --accent-purple: #8B5CF6;
    --accent-teal: #06B6D4;
    --accent-red: #EF4444;

    /* Neutral Colors */
    --bg-body: #F0F4FA;
    --bg-white: #FFFFFF;
    --bg-light: #F8FAFC;
    --text-primary: #1E293B;
    --text-secondary: #64748B;
    --text-muted: #94A3B8;
    --border-color: #E2E8F0;

    /* Shadows */
    --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.06);
    --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.08);
    --shadow-lg: 0 8px 30px rgba(0, 0, 0, 0.1);
    --shadow-xl: 0 20px 60px rgba(0, 0, 0, 0.12);

    /* Border Radius */
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 16px;
    --radius-xl: 24px;

    /* Transitions */
    --transition-fast: 0.2s ease;
    --transition-normal: 0.3s ease;
    --transition-slow: 0.5s ease;

    /* Font Sizes */
    --font-xs: 12px;
    --font-sm: 14px;
    --font-base: 16px;
    --font-md: 18px;
    --font-lg: 20px;
    --font-xl: 24px;
    --font-2xl: 30px;
    --font-3xl: 36px;

    /* Spacing */
    --spacing-xs: 4px;
    --spacing-sm: 8px;
    --spacing-md: 16px;
    --spacing-lg: 24px;
    --spacing-xl: 32px;
    --spacing-2xl: 48px;

    /* Container */
    --container-max: 1200px;
}

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

html {
    scroll-behavior: smooth;
    font-size: var(--font-base);
}

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Helvetica Neue", Helvetica, Arial, sans-serif;
    color: var(--text-primary);
    background-color: var(--bg-body);
    line-height: 1.6;
    -webkit-font-smoothing: antialiased;
}

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

ul, ol {
    list-style: none;
}

img {
    max-width: 100%;
    height: auto;
    display: block;
}

/* Container */
.container {
    width: 100%;
    max-width: var(--container-max);
    margin: 0 auto;
    padding: 0 var(--spacing-md);
}

/* ========================================
   Header
======================================== */
.header {
    background: var(--bg-white);
    box-shadow: var(--shadow-sm);
    position: sticky;
    top: 0;
    z-index: 1000;
    transition: box-shadow var(--transition-normal);
}

.header-inner {
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 80px;
}

.logo-link {
    flex-shrink: 0;
}

.logo-img {
    height: 52px;
    width: auto;
}

/* Navigation */
.main-nav .nav-list {
    display: flex;
    align-items: center;
    gap: var(--spacing-xs);
}

.nav-link {
    display: block;
    padding: var(--spacing-sm) var(--spacing-md);
    font-size: var(--font-base);
    color: var(--text-primary);
    position: relative;
    border-radius: var(--radius-sm);
    transition: all var(--transition-fast);
}

.nav-link::after {
    content: '';
    position: absolute;
    bottom: 2px;
    left: 50%;
    transform: translateX(-50%) scaleX(0);
    width: calc(100% - var(--spacing-md));
    height: 3px;
    background: linear-gradient(90deg, var(--primary), var(--accent-teal));
    border-radius: 2px;
    transition: transform var(--transition-normal);
}

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

.nav-link:hover::after {
    transform: translateX(-50%) scaleX(1);
}

.nav-link.active {
    color: var(--primary);
    font-weight: 600;
}

.nav-link.active::after {
    transform: translateX(-50%) scaleX(1);
}

/* Hamburger */
.hamburger {
    display: none;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    width: 40px;
    height: 40px;
    background: none;
    border: none;
    cursor: pointer;
    padding: var(--spacing-sm);
    gap: 5px;
}

.hamburger span {
    display: block;
    width: 24px;
    height: 2.5px;
    background-color: var(--text-primary);
    border-radius: 2px;
    transition: all var(--transition-normal);
}

/* Mobile Menu Overlay */
.mobile-menu-overlay {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(30, 41, 59, 0.6);
    backdrop-filter: blur(8px);
    -webkit-backdrop-filter: blur(8px);
    z-index: 2000;
    opacity: 0;
    visibility: hidden;
    transition: all var(--transition-normal);
}

.mobile-menu-overlay.active {
    opacity: 1;
    visibility: visible;
}

.mobile-menu-content {
    position: absolute;
    top: 0;
    right: 0;
    width: 300px;
    max-width: 85%;
    height: 100%;
    background: var(--bg-white);
    padding: var(--spacing-xl) var(--spacing-lg);
    transform: translateX(100%);
    transition: transform var(--transition-normal);
    overflow-y: auto;
}

.mobile-menu-overlay.active .mobile-menu-content {
    transform: translateX(0);
}

.close-btn {
    position: absolute;
    top: var(--spacing-md);
    right: var(--spacing-md);
    width: 36px;
    height: 36px;
    background: var(--bg-light);
    border: none;
    border-radius: 50%;
    font-size: 20px;
    color: var(--text-secondary);
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all var(--transition-fast);
}

.close-btn:hover {
    background: var(--primary-lighter);
    color: var(--primary);
}

.mobile-nav-list li {
    border-bottom: 1px solid var(--border-color);
}

.mobile-nav-link {
    display: block;
    padding: var(--spacing-md) 0;
    font-size: var(--font-lg);
    color: var(--text-primary);
    transition: all var(--transition-fast);
}

.mobile-nav-link:hover,
.mobile-nav-link.active {
    color: var(--primary);
    padding-left: var(--spacing-sm);
}

/* ========================================
   Footer
======================================== */
.footer {
    background: linear-gradient(135deg, var(--primary-darker) 0%, var(--primary-dark) 50%, var(--primary) 100%);
    color: #FFFFFF;
    padding-top: var(--spacing-2xl);
    margin-top: var(--spacing-2xl);
}

.footer-grid {
    display: grid;
    grid-template-columns: 1fr 1fr 1fr 2fr; 
    gap: var(--spacing-xl);
    padding-bottom: var(--spacing-xl);
}

.footer-title {
    font-size: var(--font-md);
    font-weight: 600;
    margin-bottom: var(--spacing-lg);
    position: relative;
    padding-bottom: var(--spacing-sm);
}

.footer-title::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 0;
    width: 40px;
    height: 3px;
    background: linear-gradient(90deg, var(--accent-green), var(--accent-teal));
    border-radius: 2px;
}

.footer-info-list li {
    padding: var(--spacing-xs) 0;
    font-size: var(--font-sm);
    line-height: 1.8;
    opacity: 0.9;
}

.info-label {
    color: rgba(255, 255, 255, 0.7);
}

.footer-link-list li {
    padding: var(--spacing-xs) 0;
}

.footer-link-list a {
    font-size: var(--font-sm);
    opacity: 0.85;
    transition: all var(--transition-fast);
    position: relative;
    display: inline-block;
}

.footer-link-list a::after {
    content: '';
    position: absolute;
    bottom: -2px;
    left: 0;
    width: 0;
    height: 1.5px;
    background: var(--accent-green);
    transition: width var(--transition-normal);
}

.footer-link-list a:hover {
    opacity: 1;
    color: var(--accent-green);
}

.footer-link-list a:hover::after {
    width: 100%;
}

/* QR Grid */
.qr-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: var(--spacing-sm);
}

.qr-item img {
    width: 160px;
    height: 160px;
    border-radius: var(--radius-sm);
    background: rgba(255, 255, 255, 0.15);
    padding: var(--spacing-xs);
    transition: transform var(--transition-fast);
}

.qr-item img:hover {
    transform: scale(1.2);
}

/* Copyright */
.footer-copyright {
    text-align: center;
    padding: var(--spacing-lg) 0;
    border-top: 1px solid rgba(255, 255, 255, 0.15);
    font-size: var(--font-sm);
    opacity: 0.75;
}

/* ========================================
   Page Header (List & Content)
======================================== */
.page-header {
    background: linear-gradient(135deg, var(--primary-dark), var(--primary));
    padding: var(--spacing-xl) 0;
    color: #FFFFFF;
}

.page-title {
    font-size: var(--font-2xl);
    font-weight: 700;
    margin-bottom: var(--spacing-sm);
}

.page-breadcrumb {
    font-size: var(--font-sm);
    opacity: 0.85;
}

.page-breadcrumb a {
    color: rgba(255, 255, 255, 0.9);
    transition: color var(--transition-fast);
}

.page-breadcrumb a:hover {
    color: #FFFFFF;
}

/* ========================================
   Sidebar Common Styles
======================================== */
.sidebar-block {
    background: var(--bg-white);
    border-radius: var(--radius-md);
    padding: var(--spacing-lg);
    margin-bottom: var(--spacing-lg);
    box-shadow: var(--shadow-sm);
}

.sidebar-title {
    font-size: var(--font-base);
    font-weight: 600;
    margin-bottom: var(--spacing-md);
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
}

.title-bar {
    width: 4px;
    height: 18px;
    background: linear-gradient(180deg, var(--primary), var(--accent-teal));
    border-radius: 2px;
    flex-shrink: 0;
}

.sidebar-nav-list li {
    border-bottom: 1px solid var(--border-color);
}

.sidebar-nav-list li:last-child {
    border-bottom: none;
}

.sidebar-nav-link {
    display: block;
    padding: var(--spacing-sm) 0;
    font-size: var(--font-sm);
    color: var(--text-secondary);
    transition: all var(--transition-fast);
    position: relative;
    padding-left: var(--spacing-md);
}

.sidebar-nav-link::before {
    content: '';
    position: absolute;
    left: 0;
    top: 50%;
    transform: translateY(-50%);
    width: 6px;
    height: 6px;
    border-radius: 50%;
    background: var(--border-color);
    transition: all var(--transition-fast);
}

.sidebar-nav-link:hover {
    color: var(--primary);
    padding-left: calc(var(--spacing-md) + 4px);
}

.sidebar-nav-link:hover::before {
    background: var(--primary);
}

.sidebar-nav-link.active {
    color: var(--primary);
    font-weight: 600;
}

.sidebar-nav-link.active::before {
    background: var(--primary);
    width: 8px;
    height: 8px;
}

/* ========================================
   Responsive - Tablet (≤960px)
======================================== */
@media (max-width: 960px) {
    .main-nav {
        display: none;
    }

    .hamburger {
        display: flex;
    }

    .header-inner {
        height: 70px;
    }

    .logo-img {
        height: 42px;
    }

    .footer-grid {
        grid-template-columns: 1fr 2fr;
    }
}

/* ========================================
   Responsive - Mobile (≤640px)
======================================== */
@media (max-width: 640px) {
    :root {
        --font-base: 15px;
    }

    .header-inner {
        height: 60px;
    }

    .logo-img {
        height: 36px;
    }

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

    .page-title {
        font-size: var(--font-xl);
    }
}