/* ============================================================================
   Hardware Knowledge Base - Styles.css
   Professional CSS with modern responsive design
   ============================================================================ */

/* ============================================================================
   CSS VARIABLES - Color Scheme & Theme Configuration
   ============================================================================ */
:root {
    /* Primary Colors */
    --primary-color: #2196F3;
    --primary-dark: #1976D2;
    --primary-light: #BBDEFB;

    /* Secondary Colors */
    --secondary-color: #4CAF50;
    --secondary-dark: #388E3C;
    --secondary-light: #C8E6C9;

    /* Accent Colors */
    --accent-color: #FF9800;
    --accent-dark: #F57C00;
    --accent-light: #FFE0B2;

    /* Semantic Colors */
    --success-color: #4CAF50;
    --warning-color: #FF9800;
    --error-color: #F44336;
    --info-color: #2196F3;

    /* Neutral Colors */
    --text-primary: #212121;
    --text-secondary: #757575;
    --text-disabled: #BDBDBD;
    --text-white: #FFFFFF;

    /* Background Colors */
    --bg-primary: #FFFFFF;
    --bg-secondary: #F5F5F5;
    --bg-tertiary: #FAFAFA;
    --bg-dark: #263238;

    /* Border & Divider Colors */
    --border-color: #E0E0E0;
    --divider-color: #EEEEEE;

    /* Shadow & Elevation */
    --shadow-sm: 0 2px 4px rgba(0,0,0,0.1);
    --shadow-md: 0 4px 8px rgba(0,0,0,0.12);
    --shadow-lg: 0 8px 16px rgba(0,0,0,0.15);
    --shadow-xl: 0 12px 24px rgba(0,0,0,0.18);

    /* Typography */
    --font-primary: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    --font-monospace: 'Consolas', 'Monaco', 'Courier New', monospace;

    --font-size-xs: 0.75rem;    /* 12px */
    --font-size-sm: 0.875rem;   /* 14px */
    --font-size-base: 1rem;     /* 16px */
    --font-size-lg: 1.125rem;   /* 18px */
    --font-size-xl: 1.25rem;    /* 20px */
    --font-size-2xl: 1.5rem;    /* 24px */
    --font-size-3xl: 2rem;      /* 32px */
    --font-size-4xl: 2.5rem;    /* 40px */

    /* Spacing */
    --spacing-xs: 0.25rem;   /* 4px */
    --spacing-sm: 0.5rem;    /* 8px */
    --spacing-md: 1rem;      /* 16px */
    --spacing-lg: 1.5rem;    /* 24px */
    --spacing-xl: 2rem;      /* 32px */
    --spacing-2xl: 3rem;     /* 48px */
    --spacing-3xl: 4rem;     /* 64px */

    /* Transitions */
    --transition-fast: 150ms ease-in-out;
    --transition-base: 250ms ease-in-out;
    --transition-slow: 350ms ease-in-out;

    /* Border Radius */
    --radius-sm: 4px;
    --radius-md: 8px;
    --radius-lg: 12px;
    --radius-xl: 16px;
    --radius-full: 9999px;

    /* Container Widths */
    --container-sm: 640px;
    --container-md: 768px;
    --container-lg: 1024px;
    --container-xl: 1280px;
    --container-2xl: 1536px;

    /* Sidebar */
    --sidebar-width: 280px;
    --sidebar-bg: var(--bg-primary);
}

/* ============================================================================
   DARK MODE SUPPORT (Optional)
   ============================================================================ */
@media (prefers-color-scheme: dark) {
    :root.dark-mode {
        --primary-color: #42A5F5;
        --secondary-color: #66BB6A;
        --accent-color: #FFA726;

        --text-primary: #FAFAFA;
        --text-secondary: #B0BEC5;
        --text-disabled: #78909C;

        --bg-primary: #1A1A1A;
        --bg-secondary: #263238;
        --bg-tertiary: #2C3E50;
        --bg-dark: #0D1117;

        --border-color: #37474F;
        --divider-color: #455A64;

        --shadow-sm: 0 2px 4px rgba(0,0,0,0.3);
        --shadow-md: 0 4px 8px rgba(0,0,0,0.4);
        --shadow-lg: 0 8px 16px rgba(0,0,0,0.5);
        --shadow-xl: 0 12px 24px rgba(0,0,0,0.6);
    }
}

/* ============================================================================
   RESET & BASE STYLES
   ============================================================================ */
*, *::before, *::after {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
    font-size: 16px;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

body {
    font-family: var(--font-primary);
    font-size: var(--font-size-base);
    line-height: 1.6;
    color: var(--text-primary);
    background-color: var(--bg-secondary);
    overflow-x: hidden;
}

/* ============================================================================
   TYPOGRAPHY
   ============================================================================ */
h1, h2, h3, h4, h5, h6 {
    font-weight: 600;
    line-height: 1.3;
    margin-bottom: var(--spacing-md);
    color: var(--text-primary);
}

h1 { font-size: var(--font-size-4xl); }
h2 { font-size: var(--font-size-3xl); }
h3 { font-size: var(--font-size-2xl); }
h4 { font-size: var(--font-size-xl); }
h5 { font-size: var(--font-size-lg); }
h6 { font-size: var(--font-size-base); }

p {
    margin-bottom: var(--spacing-md);
    line-height: 1.7;
}

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

a:hover {
    color: var(--primary-dark);
    text-decoration: underline;
}

strong {
    font-weight: 600;
    color: var(--text-primary);
}

/* ============================================================================
   LAYOUT - CONTAINER
   ============================================================================ */
.container {
    width: 100%;
    max-width: var(--container-xl);
    margin: 0 auto;
    padding: 0 var(--spacing-lg);
}

@media (min-width: 1536px) {
    .container {
        max-width: var(--container-2xl);
    }
}

/* ============================================================================
   HEADER & NAVIGATION
   ============================================================================ */
.main-header {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 10000; /* 提高z-index确保在最上层 */
    background: var(--bg-primary);
    box-shadow: var(--shadow-md);
    transition: transform var(--transition-base);
    overflow: visible; /* 确保内容可见 */
}

.main-header.hidden {
    transform: translateY(-100%);
}

.navbar {
    padding: var(--spacing-md) 0;
}

.navbar .container {
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: var(--spacing-md); /* 添加间距 */
    flex-wrap: nowrap; /* 防止换行 */
}

/* Navigation Brand */
.nav-brand {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    font-size: var(--font-size-xl);
    font-weight: 700;
    color: var(--primary-color);
    cursor: pointer;
    flex-shrink: 0; /* 防止收缩 */
}

.nav-brand i {
    font-size: 1.5em;
    flex-shrink: 0; /* 防止图标收缩 */
}

.brand-title {
    color: var(--text-primary);
    white-space: nowrap; /* 防止文字换行 */
    overflow: hidden; /* 隐藏溢出 */
    text-overflow: ellipsis; /* 使用省略号 */
}

.brand-subtitle {
    font-size: var(--font-size-sm);
    color: var(--text-secondary);
    font-weight: 400;
    margin-left: var(--spacing-sm);
    white-space: nowrap; /* 防止文字换行 */
    overflow: hidden; /* 隐藏溢出 */
    text-overflow: ellipsis; /* 使用省略号 */
}

/* Navigation Toggle (Mobile) */
.nav-toggle {
    display: none;
    flex-direction: column;
    gap: 5px;
    background: none;
    border: none;
    cursor: pointer;
    padding: var(--spacing-sm);
}

.nav-toggle span {
    width: 25px;
    height: 3px;
    background: var(--text-primary);
    border-radius: var(--radius-sm);
    transition: all var(--transition-base);
}

.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);
}

/* Navigation Menu */
.nav-menu {
    display: flex;
    list-style: none;
    gap: var(--spacing-sm);
}

.nav-link {
    display: flex;
    align-items: center;
    gap: var(--spacing-xs);
    padding: var(--spacing-sm) var(--spacing-md);
    color: var(--text-secondary);
    font-weight: 500;
    border-radius: var(--radius-md);
    transition: all var(--transition-fast);
    white-space: nowrap;
}

.nav-link:hover {
    background: var(--bg-secondary);
    color: var(--primary-color);
    text-decoration: none;
}

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

.nav-link i {
    font-size: 1.1em;
}

/* Mobile Navigation */
@media (max-width: 768px) {
    .nav-toggle {
        display: flex;
    }

    .nav-menu {
        position: fixed;
        top: 70px;
        left: 0;
        right: 0;
        background: var(--bg-primary);
        flex-direction: column;
        padding: var(--spacing-lg);
        box-shadow: var(--shadow-lg);
        transform: translateX(-100%);
        transition: transform var(--transition-base);
    }

    .nav-menu.active {
        transform: translateX(0);
    }

    .brand-subtitle {
        display: none;
    }
}

/* ============================================================================
   HERO SECTION
   ============================================================================ */
.hero {
    margin-top: 70px;
    padding: var(--spacing-3xl) 0;
    background: linear-gradient(135deg, var(--primary-light) 0%, var(--bg-primary) 100%);
    overflow: hidden;
}

.hero .container {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: var(--spacing-2xl);
    align-items: center;
}

.hero-content h1 {
    font-size: var(--font-size-4xl);
    margin-bottom: var(--spacing-md);
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.hero-subtitle {
    font-size: var(--font-size-xl);
    color: var(--text-secondary);
    margin-bottom: var(--spacing-xl);
}

/* Hero Stats */
.hero-stats {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: var(--spacing-lg);
    margin: var(--spacing-xl) 0;
}

.stat-item {
    display: flex;
    align-items: center;
    gap: var(--spacing-md);
    padding: var(--spacing-md);
    background: var(--bg-primary);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-sm);
    transition: transform var(--transition-base), box-shadow var(--transition-base);
}

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

.stat-item i {
    font-size: 2rem;
    color: var(--primary-color);
}

.stat-info {
    display: flex;
    flex-direction: column;
}

.stat-info strong {
    font-size: var(--font-size-xl);
    color: var(--text-primary);
}

.stat-info span {
    font-size: var(--font-size-sm);
    color: var(--text-secondary);
}

/* Hero CTA Buttons */
.hero-cta {
    display: flex;
    gap: var(--spacing-md);
    margin-top: var(--spacing-xl);
}

/* Hero Illustration */
.hero-image {
    display: flex;
    justify-content: center;
    align-items: center;
}

.circuit-illustration {
    width: 100%;
    max-width: 600px;
    height: auto;
}

/* SVG Animations */
.chip-animation {
    animation: pulse 2s ease-in-out infinite;
}

@keyframes pulse {
    0%, 100% { opacity: 1; }
    50% { opacity: 0.7; }
}

.signal-flow .pulse {
    animation: signalPulse 2s ease-in-out infinite;
}

@keyframes signalPulse {
    0%, 100% { r: 4; opacity: 1; }
    50% { r: 8; opacity: 0.3; }
}

.waveform {
    animation: waveMove 1s linear infinite;
    stroke-dasharray: 200;
    stroke-dashoffset: 200;
}

@keyframes waveMove {
    to { stroke-dashoffset: 0; }
}

/* Hero Responsive */
@media (max-width: 768px) {
    .hero .container {
        grid-template-columns: 1fr;
    }

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

    .hero-content h1 {
        font-size: var(--font-size-3xl);
    }

    .hero-subtitle {
        font-size: var(--font-size-lg);
    }

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

    .hero-image {
        order: -1;
    }
}

/* ============================================================================
   BUTTONS
   ============================================================================ */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: var(--spacing-sm);
    padding: var(--spacing-sm) var(--spacing-lg);
    font-size: var(--font-size-base);
    font-weight: 500;
    line-height: 1.5;
    text-align: center;
    border: 2px solid transparent;
    border-radius: var(--radius-md);
    cursor: pointer;
    transition: all var(--transition-base);
    text-decoration: none;
    white-space: nowrap;
}

.btn:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
    text-decoration: none;
}

.btn:active {
    transform: translateY(0);
}

/* Button Variants */
.btn-primary {
    background: var(--primary-color);
    color: var(--text-white);
    border-color: var(--primary-color);
}

.btn-primary:hover {
    background: var(--primary-dark);
    border-color: var(--primary-dark);
    color: var(--text-white);
}

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

.btn-secondary:hover {
    background: var(--secondary-dark);
    border-color: var(--secondary-dark);
    color: var(--text-white);
}

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

.btn-outline:hover {
    background: var(--primary-color);
    color: var(--text-white);
}

/* Button Sizes */
.btn-sm {
    padding: var(--spacing-xs) var(--spacing-md);
    font-size: var(--font-size-sm);
}

.btn-lg {
    padding: var(--spacing-md) var(--spacing-xl);
    font-size: var(--font-size-lg);
}

/* ============================================================================
   KNOWLEDGE NAVIGATION CARDS
   ============================================================================ */
.knowledge-nav {
    padding: var(--spacing-3xl) 0;
    background: var(--bg-primary);
}

.section-title {
    text-align: center;
    font-size: var(--font-size-3xl);
    margin-bottom: var(--spacing-2xl);
    color: var(--text-primary);
}

.nav-cards {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: var(--spacing-xl);
}

.nav-card {
    background: var(--bg-primary);
    border: 2px solid var(--border-color);
    border-radius: var(--radius-xl);
    padding: var(--spacing-xl);
    text-align: center;
    transition: all var(--transition-base);
    cursor: pointer;
}

.nav-card:hover {
    transform: translateY(-8px);
    box-shadow: var(--shadow-xl);
    border-color: var(--primary-color);
}

.card-icon {
    width: 80px;
    height: 80px;
    margin: 0 auto var(--spacing-lg);
    border-radius: var(--radius-full);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 2rem;
    color: var(--text-white);
    transition: transform var(--transition-base);
}

.nav-card:hover .card-icon {
    transform: scale(1.1) rotate(5deg);
}

.card-icon.basic {
    background: linear-gradient(135deg, var(--secondary-color), var(--secondary-dark));
}

.card-icon.intermediate {
    background: linear-gradient(135deg, var(--accent-color), var(--accent-dark));
}

.card-icon.advanced {
    background: linear-gradient(135deg, var(--error-color), #D32F2F);
}

.nav-card h3 {
    font-size: var(--font-size-2xl);
    margin-bottom: var(--spacing-sm);
}

.progress-text {
    color: var(--text-secondary);
    font-size: var(--font-size-sm);
    margin-bottom: var(--spacing-lg);
}

.card-list {
    list-style: none;
    text-align: left;
    margin-bottom: var(--spacing-lg);
}

.card-list li {
    padding: var(--spacing-sm) 0;
    color: var(--text-secondary);
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
}

.card-list i {
    color: var(--success-color);
}

/* Nav Cards Responsive */
@media (max-width: 1024px) {
    .nav-cards {
        grid-template-columns: 1fr;
    }
}

/* ============================================================================
   MAIN CONTENT LAYOUT
   ============================================================================ */
.main-content {
    padding: var(--spacing-2xl) 0;
    background: var(--bg-secondary);
}

.content-layout {
    display: grid;
    grid-template-columns: var(--sidebar-width) 1fr;
    gap: var(--spacing-xl);
    align-items: start;
}

/* ============================================================================
   SIDEBAR - STICKY NAVIGATION
   ============================================================================ */
.sidebar {
    position: sticky;
    top: 90px;
    max-height: calc(100vh - 110px);
    overflow-y: auto;
    background: var(--sidebar-bg);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-md);
    padding: var(--spacing-lg);
}

.sidebar::-webkit-scrollbar {
    width: 6px;
}

.sidebar::-webkit-scrollbar-track {
    background: var(--bg-secondary);
    border-radius: var(--radius-sm);
}

.sidebar::-webkit-scrollbar-thumb {
    background: var(--border-color);
    border-radius: var(--radius-sm);
}

.sidebar::-webkit-scrollbar-thumb:hover {
    background: var(--text-disabled);
}

.sidebar-sticky h3 {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    font-size: var(--font-size-xl);
    margin-bottom: var(--spacing-lg);
    color: var(--text-primary);
    padding-bottom: var(--spacing-md);
    border-bottom: 2px solid var(--divider-color);
}

/* TOC Navigation */
.toc-nav {
    margin-bottom: var(--spacing-xl);
}

.toc-section {
    margin-bottom: var(--spacing-md);
}

.toc-header {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    padding: var(--spacing-md);
    background: var(--bg-secondary);
    border-radius: var(--radius-md);
    cursor: pointer;
    font-weight: 600;
    color: var(--text-primary);
    transition: all var(--transition-fast);
}

.toc-header:hover {
    background: var(--primary-light);
    color: var(--primary-dark);
}

.toc-header .toggle-icon {
    margin-left: auto;
    transition: transform var(--transition-base);
}

.toc-section.active .toggle-icon {
    transform: rotate(180deg);
}

/* 一级目录：默认折叠 */
.toc-items {
    display: none; /* ✅ 默认完全隐藏 */
    list-style: none;
}

/* 一级目录：展开状态 */
.toc-items.active {
    display: block; /* ✅ 展开时显示 */
    margin-top: var(--spacing-sm);
    animation: slideDown 0.2s ease-out; /* 与子项使用相同动画 */
}

.toc-items li {
    margin: 0;
}

.toc-items a {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    padding: var(--spacing-sm) var(--spacing-md);
    color: var(--text-secondary);
    border-radius: var(--radius-sm);
    transition: all var(--transition-fast);
    font-size: var(--font-size-sm);
}

.toc-items a:hover {
    background: var(--bg-secondary);
    color: var(--primary-color);
    text-decoration: none;
    padding-left: var(--spacing-lg);
}

.toc-items a.active {
    background: var(--primary-light);
    color: var(--primary-dark);
    font-weight: 600;
}

/* Multi-level TOC Navigation */
.toc-item-group {
    margin-bottom: var(--spacing-sm);
}

.toc-group-link {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    padding: var(--spacing-sm) var(--spacing-md);
    color: var(--text-primary);
    font-weight: 600;
    border-radius: var(--radius-sm);
    transition: all var(--transition-fast);
    font-size: var(--font-size-base);
    background: var(--bg-secondary);
    cursor: pointer; /* 添加点击指示 */
    position: relative; /* 为伪元素定位 */
}

.toc-group-link:hover {
    background: var(--primary-light);
    color: var(--primary-dark);
    text-decoration: none;
    transform: translateX(4px);
}

.toc-group-link i {
    font-size: 1.1em;
    width: 20px;
    text-align: center;
}

/* 添加展开/收起箭头指示器 */
.toc-group-link::after {
    content: '\f078'; /* Font Awesome chevron-down (折叠状态) */
    font-family: 'Font Awesome 6 Free';
    font-weight: 900;
    margin-left: auto;
    font-size: 0.8em;
    transition: all var(--transition-fast);
    color: var(--text-secondary);
}

/* 展开状态：改变图标提示可以点击跳转 */
.toc-item-group.expanded .toc-group-link::after {
    content: '\f35d'; /* Font Awesome arrow-circle-right (展开状态，提示可跳转) */
    color: var(--primary-color);
    transform: scale(1.1);
}

/* 展开状态下hover效果：强调可跳转 */
.toc-item-group.expanded .toc-group-link:hover::after {
    color: var(--primary-dark);
    transform: scale(1.2) translateX(3px);
}

/* 子项默认折叠（完全隐藏） */
.toc-sub-items {
    display: none; /* ✅ 默认完全隐藏，无动画 */
    list-style: none;
    margin: var(--spacing-xs) 0 0 0;
    padding-left: 32px;
}

/* 点击展开后才显示子项 */
.toc-item-group.expanded .toc-sub-items {
    display: block; /* ✅ 展开时显示 */
    animation: slideDown 0.2s ease-out; /* 添加简单的下滑动画 */
}

/* 下滑动画 */
@keyframes slideDown {
    from {
        opacity: 0;
        transform: translateY(-10px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.toc-sub-items li {
    margin: 0;
}

.toc-sub-items a {
    display: block;
    padding: var(--spacing-xs) var(--spacing-sm);
    color: var(--text-secondary);
    font-size: var(--font-size-sm);
    border-left: 2px solid transparent;
    transition: all var(--transition-fast);
    margin-bottom: 2px;
}

.toc-sub-items a:hover {
    color: var(--primary-color);
    background: var(--bg-hover);
    border-left-color: var(--primary-color);
    padding-left: var(--spacing-md);
    text-decoration: none;
}

.toc-sub-items a.active {
    color: var(--primary-dark);
    background: var(--primary-light);
    border-left-color: var(--primary-color);
    font-weight: 600;
}

/* Sidebar Tools */
.sidebar-tools {
    padding-top: var(--spacing-lg);
    border-top: 2px solid var(--divider-color);
}

.sidebar-tools h4 {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    font-size: var(--font-size-lg);
    margin-bottom: var(--spacing-md);
}

.tool-link {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    padding: var(--spacing-sm) var(--spacing-md);
    margin-bottom: var(--spacing-xs);
    color: var(--text-secondary);
    border-radius: var(--radius-sm);
    transition: all var(--transition-fast);
    font-size: var(--font-size-sm);
}

.tool-link:hover {
    background: var(--secondary-light);
    color: var(--secondary-dark);
    text-decoration: none;
    padding-left: var(--spacing-lg);
}

/* Sidebar Responsive */
@media (max-width: 1024px) {
    .content-layout {
        grid-template-columns: 1fr;
    }

    .sidebar {
        position: relative;
        top: 0;
        max-height: none;
    }
}

/* ============================================================================
   CONTENT AREA
   ============================================================================ */
.content-area {
    background: var(--bg-primary);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-md);
    padding: var(--spacing-2xl);
}

.content-section {
    margin-bottom: var(--spacing-3xl);
}

.content-section:last-child {
    margin-bottom: 0;
}

.section-header {
    margin-bottom: var(--spacing-xl);
    padding-bottom: var(--spacing-lg);
    border-bottom: 3px solid var(--divider-color);
}

.section-header h2 {
    display: flex;
    align-items: center;
    gap: var(--spacing-md);
    margin-bottom: var(--spacing-sm);
}

.section-desc {
    font-size: var(--font-size-lg);
    color: var(--text-secondary);
    margin: 0;
}

/* ============================================================================
   KNOWLEDGE ARTICLES
   ============================================================================ */
.knowledge-article {
    margin-bottom: var(--spacing-3xl);
    padding-bottom: var(--spacing-3xl);
    border-bottom: 1px solid var(--divider-color);
}

.knowledge-article:last-child {
    border-bottom: none;
    padding-bottom: 0;
}

.article-header {
    margin-bottom: var(--spacing-xl);
}

.article-header h3 {
    display: flex;
    align-items: center;
    gap: var(--spacing-md);
    color: var(--text-primary);
}

.article-meta {
    display: flex;
    flex-wrap: wrap;
    gap: var(--spacing-md);
    margin-top: var(--spacing-md);
}

.article-meta span {
    display: inline-flex;
    align-items: center;
    gap: var(--spacing-xs);
    padding: var(--spacing-xs) var(--spacing-md);
    font-size: var(--font-size-sm);
    border-radius: var(--radius-full);
}

.difficulty {
    font-weight: 600;
}

.difficulty.easy {
    background: var(--secondary-light);
    color: var(--secondary-dark);
}

.difficulty.medium {
    background: var(--accent-light);
    color: var(--accent-dark);
}

.difficulty.hard {
    background: #FFCDD2;
    color: #C62828;
}

.read-time {
    background: var(--bg-secondary);
    color: var(--text-secondary);
}

.updated {
    background: var(--bg-secondary);
    color: var(--text-secondary);
}

/* Article Content */
.article-content {
    line-height: 1.8;
}

.article-content h4 {
    margin-top: var(--spacing-2xl);
    margin-bottom: var(--spacing-lg);
    color: var(--primary-dark);
    font-size: var(--font-size-xl);
}

.article-content h5 {
    margin-top: var(--spacing-lg);
    margin-bottom: var(--spacing-md);
    color: var(--text-primary);
}

.content-block {
    margin-bottom: var(--spacing-xl);
}

.separator {
    height: 2px;
    background: linear-gradient(90deg, transparent, var(--divider-color), transparent);
    margin: var(--spacing-2xl) 0;
}

/* ============================================================================
   FORMULA BOXES
   ============================================================================ */
.formula-box {
    background: linear-gradient(135deg, #E3F2FD, #F3E5F5);
    border-left: 4px solid var(--primary-color);
    border-radius: var(--radius-md);
    padding: var(--spacing-lg);
    margin: var(--spacing-lg) 0;
}

.formula-title {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    font-weight: 600;
    font-size: var(--font-size-lg);
    color: var(--primary-dark);
    margin-bottom: var(--spacing-md);
}

.formula-content {
    font-size: var(--font-size-lg);
    text-align: center;
    padding: var(--spacing-md);
}

.formula-desc {
    font-size: var(--font-size-sm);
    color: var(--text-secondary);
    text-align: left;
    margin-top: var(--spacing-md);
    margin-bottom: 0;
}

.formula-inline {
    display: inline-block;
    padding: var(--spacing-sm) var(--spacing-md);
    background: var(--bg-secondary);
    border-radius: var(--radius-sm);
    margin: var(--spacing-sm) 0;
}

/* ============================================================================
   INFO CARDS & GRIDS
   ============================================================================ */
.info-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: var(--spacing-lg);
    margin: var(--spacing-lg) 0;
}

.info-card {
    background: var(--bg-tertiary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: var(--spacing-lg);
    transition: all var(--transition-base);
}

.info-card:hover {
    box-shadow: var(--shadow-md);
    border-color: var(--primary-light);
}

.info-card h5 {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    font-size: var(--font-size-lg);
    color: var(--primary-dark);
    margin-bottom: var(--spacing-md);
}

.info-card ul {
    list-style: none;
}

.info-card ul li {
    padding: var(--spacing-xs) 0;
    color: var(--text-secondary);
}

/* ============================================================================
   TABLES
   ============================================================================ */
.info-table {
    width: 100%;
    border-collapse: collapse;
    margin: var(--spacing-md) 0;
    font-size: var(--font-size-sm);
}

.info-table thead {
    background: var(--primary-color);
    color: var(--text-white);
}

.info-table th {
    padding: var(--spacing-md);
    text-align: left;
    font-weight: 600;
}

.info-table td {
    padding: var(--spacing-md);
    border-bottom: 1px solid var(--divider-color);
}

.info-table tbody tr {
    transition: background var(--transition-fast);
}

.info-table tbody tr:hover {
    background: var(--bg-secondary);
}

/* ============================================================================
   DIAGRAMS & SVG COMPONENTS
   ============================================================================ */
.diagram-box {
    background: var(--bg-tertiary);
    border: 2px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: var(--spacing-lg);
    margin: var(--spacing-lg) 0;
}

.diagram-box h5 {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    margin-bottom: var(--spacing-md);
}

.component-diagram,
.circuit-diagram {
    width: 100%;
    height: auto;
    background: var(--bg-primary);
    border-radius: var(--radius-md);
}

/* ============================================================================
   REFERENCE BOXES
   ============================================================================ */
.reference-box {
    background: var(--bg-secondary);
    border-left: 4px solid var(--info-color);
    border-radius: var(--radius-md);
    padding: var(--spacing-lg);
    margin: var(--spacing-lg) 0;
}

.reference-box h5 {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    color: var(--info-color);
    margin-bottom: var(--spacing-md);
}

.reference-box ul {
    list-style: none;
}

.reference-box li {
    margin-bottom: var(--spacing-sm);
}

.reference-box a {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    color: var(--primary-color);
    padding: var(--spacing-xs) 0;
}

.reference-box a:hover {
    color: var(--primary-dark);
}

/* ============================================================================
   CALCULATOR WIDGET
   ============================================================================ */
.calculator-widget {
    background: linear-gradient(135deg, #FFF3E0, #E8F5E9);
    border: 2px solid var(--accent-light);
    border-radius: var(--radius-lg);
    overflow: hidden;
    margin: var(--spacing-lg) 0;
}

.widget-header {
    background: var(--accent-color);
    color: var(--text-white);
    padding: var(--spacing-md) var(--spacing-lg);
    font-weight: 600;
    font-size: var(--font-size-lg);
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
}

.widget-body {
    padding: var(--spacing-lg);
}

.calc-input-group {
    margin-bottom: var(--spacing-md);
}

.calc-input-group label {
    display: block;
    font-weight: 600;
    margin-bottom: var(--spacing-xs);
    color: var(--text-primary);
}

.calc-input-group input {
    width: 100%;
    padding: var(--spacing-sm) var(--spacing-md);
    border: 2px solid var(--border-color);
    border-radius: var(--radius-md);
    font-size: var(--font-size-base);
    transition: border-color var(--transition-fast);
}

.calc-input-group input:focus {
    outline: none;
    border-color: var(--primary-color);
}

.calc-result {
    margin-top: var(--spacing-lg);
    padding: var(--spacing-lg);
    background: var(--bg-primary);
    border-radius: var(--radius-md);
    border: 2px solid var(--success-color);
}

.calc-result h5 {
    color: var(--success-color);
    margin-bottom: var(--spacing-md);
}

.calc-result p {
    margin-bottom: var(--spacing-sm);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.calc-result span {
    font-weight: 600;
    color: var(--primary-dark);
}

/* ============================================================================
   PRACTICAL EXAMPLES
   ============================================================================ */
.practical-example {
    background: var(--bg-tertiary);
    border-radius: var(--radius-lg);
    padding: var(--spacing-lg);
    margin: var(--spacing-lg) 0;
}

.practical-example h5 {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    color: var(--accent-dark);
    margin-bottom: var(--spacing-md);
}

.example-card {
    background: var(--bg-primary);
    border: 2px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: var(--spacing-lg);
}

.example-card h6 {
    color: var(--primary-dark);
    margin-bottom: var(--spacing-md);
    font-size: var(--font-size-lg);
}

.example-card ul {
    margin-left: var(--spacing-lg);
    color: var(--text-secondary);
}

/* ============================================================================
   FAQ ACCORDION
   ============================================================================ */
.faq-section {
    margin-top: var(--spacing-2xl);
}

.faq-section h4 {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    margin-bottom: var(--spacing-lg);
    color: var(--primary-dark);
}

.faq-item {
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    margin-bottom: var(--spacing-md);
    overflow: hidden;
}

.faq-question {
    display: flex;
    align-items: center;
    gap: var(--spacing-md);
    padding: var(--spacing-md) var(--spacing-lg);
    background: var(--bg-secondary);
    cursor: pointer;
    font-weight: 600;
    transition: all var(--transition-fast);
}

.faq-question:hover {
    background: var(--primary-light);
    color: var(--primary-dark);
}

.faq-question i {
    transition: transform var(--transition-base);
    color: var(--primary-color);
}

.faq-item.active .faq-question i {
    transform: rotate(90deg);
}

.faq-answer {
    max-height: 0;
    overflow: hidden;
    transition: max-height var(--transition-base);
    background: var(--bg-primary);
}

.faq-item.active .faq-answer {
    max-height: 500px;
    padding: var(--spacing-lg);
}

.faq-answer ul {
    margin-left: var(--spacing-lg);
    margin-bottom: var(--spacing-md);
}

/* ============================================================================
   INTERACTIVE EXAMPLES
   ============================================================================ */
.interactive-example {
    background: linear-gradient(135deg, #F3E5F5, #E1F5FE);
    border-radius: var(--radius-lg);
    padding: var(--spacing-lg);
    margin: var(--spacing-lg) 0;
}

.interactive-example h5 {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    color: var(--primary-dark);
    margin-bottom: var(--spacing-md);
}

.circuit-simulator {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: var(--spacing-lg);
    align-items: center;
}

@media (max-width: 768px) {
    .circuit-simulator {
        grid-template-columns: 1fr;
        gap: var(--spacing-md);
    }
}

.simulator-result {
    background: var(--bg-primary);
    border-radius: var(--radius-md);
    padding: var(--spacing-lg);
}

.law-box {
    background: var(--bg-tertiary);
    border-left: 4px solid var(--secondary-color);
    border-radius: var(--radius-md);
    padding: var(--spacing-lg);
    margin: var(--spacing-lg) 0;
}

.law-box h5 {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    color: var(--secondary-dark);
    margin-bottom: var(--spacing-md);
}

/* ============================================================================
   TOOLS SECTION
   ============================================================================ */
.tools-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: var(--spacing-lg);
    margin-top: var(--spacing-xl);
}

.tool-card {
    background: var(--bg-primary);
    border: 2px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: var(--spacing-xl);
    text-align: center;
    transition: all var(--transition-base);
}

.tool-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-lg);
    border-color: var(--primary-color);
}

.tool-icon {
    width: 60px;
    height: 60px;
    margin: 0 auto var(--spacing-md);
    background: var(--primary-light);
    border-radius: var(--radius-full);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.5rem;
    color: var(--primary-color);
    transition: all var(--transition-base);
}

.tool-card:hover .tool-icon {
    transform: scale(1.1);
    background: var(--primary-color);
    color: var(--text-white);
}

.tool-card h4 {
    margin-bottom: var(--spacing-sm);
    color: var(--text-primary);
}

.tool-card p {
    color: var(--text-secondary);
    margin-bottom: var(--spacing-lg);
}

/* ============================================================================
   KNOWLEDGE GRAPH
   ============================================================================ */
.graph-container {
    background: var(--bg-primary);
    border: 2px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: var(--spacing-xl);
    margin-top: var(--spacing-xl);
}

.knowledge-graph-svg {
    width: 100%;
    height: auto;
    border-radius: var(--radius-md);
    background: var(--bg-tertiary);
}

.graph-node circle {
    cursor: pointer;
    transition: all var(--transition-base);
}

.graph-node:hover circle {
    r: 50;
    filter: drop-shadow(0 0 10px rgba(33, 150, 243, 0.5));
}

.graph-legend {
    margin-top: var(--spacing-lg);
    padding: var(--spacing-lg);
    background: var(--bg-secondary);
    border-radius: var(--radius-md);
}

.graph-legend h4 {
    margin-bottom: var(--spacing-md);
}

.legend-item {
    display: flex;
    align-items: center;
    gap: var(--spacing-md);
    margin-bottom: var(--spacing-sm);
}

.legend-color {
    width: 20px;
    height: 20px;
    border-radius: var(--radius-sm);
}

/* ============================================================================
   COMING SOON PLACEHOLDER
   ============================================================================ */
.coming-soon-box {
    text-align: center;
    padding: var(--spacing-3xl);
    background: var(--bg-secondary);
    border-radius: var(--radius-lg);
    border: 2px dashed var(--border-color);
}

.coming-soon-box i {
    font-size: 4rem;
    color: var(--text-disabled);
    margin-bottom: var(--spacing-lg);
}

.coming-soon-box h3 {
    color: var(--text-secondary);
    margin-bottom: var(--spacing-md);
}

.coming-soon-box p {
    color: var(--text-secondary);
    margin: 0;
}

/* ============================================================================
   FOOTER
   ============================================================================ */
.main-footer {
    background: var(--bg-dark);
    color: var(--text-white);
    padding: var(--spacing-3xl) 0 var(--spacing-lg);
    margin-top: var(--spacing-3xl);
}

.footer-content {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: var(--spacing-2xl);
    margin-bottom: var(--spacing-2xl);
}

.footer-section h4 {
    color: var(--text-white);
    margin-bottom: var(--spacing-md);
    font-size: var(--font-size-lg);
}

.footer-section p {
    color: var(--text-disabled);
    line-height: 1.6;
}

.social-links {
    display: flex;
    gap: var(--spacing-md);
    margin-top: var(--spacing-md);
}

.social-links a {
    width: 40px;
    height: 40px;
    border-radius: var(--radius-full);
    background: rgba(255, 255, 255, 0.1);
    display: flex;
    align-items: center;
    justify-content: center;
    color: var(--text-white);
    font-size: 1.2rem;
    transition: all var(--transition-base);
}

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

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

.footer-links li {
    margin-bottom: var(--spacing-sm);
}

.footer-links a {
    color: var(--text-disabled);
    transition: color var(--transition-fast);
}

.footer-links a:hover {
    color: var(--primary-light);
    text-decoration: none;
}

.footer-bottom {
    text-align: center;
    padding-top: var(--spacing-xl);
    border-top: 1px solid rgba(255, 255, 255, 0.1);
}

.footer-bottom p {
    color: var(--text-disabled);
    margin-bottom: var(--spacing-sm);
}

.disclaimer {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: var(--spacing-sm);
    font-size: var(--font-size-sm);
}

/* Footer Responsive */
@media (max-width: 1024px) {
    .footer-content {
        grid-template-columns: repeat(2, 1fr);
    }
}

@media (max-width: 640px) {
    .footer-content {
        grid-template-columns: 1fr;
    }
}

/* ============================================================================
   BACK TO TOP BUTTON
   ============================================================================ */
.back-to-top {
    position: fixed;
    bottom: 30px;
    right: 30px;
    width: 50px;
    height: 50px;
    background: var(--primary-color);
    color: var(--text-white);
    border: none;
    border-radius: var(--radius-full);
    font-size: 1.2rem;
    cursor: pointer;
    opacity: 0;
    visibility: hidden;
    transition: all var(--transition-base);
    box-shadow: var(--shadow-lg);
    z-index: 999;
    overflow: hidden; /* 防止内容溢出 */
    display: flex; /* 使用flex布局 */
    align-items: center; /* 垂直居中 */
    justify-content: center; /* 水平居中 */
}

.back-to-top i {
    text-indent: 0; /* 确保图标可见 */
}

.back-to-top:hover {
    background: var(--primary-dark);
    transform: translateY(-5px);
}

.back-to-top.visible {
    opacity: 1;
    visibility: visible;
}

/* ============================================================================
   UTILITY CLASSES
   ============================================================================ */
.text-center { text-align: center; }
.text-left { text-align: left; }
.text-right { text-align: right; }

.mt-0 { margin-top: 0 !important; }
.mb-0 { margin-bottom: 0 !important; }
.mt-1 { margin-top: var(--spacing-sm); }
.mb-1 { margin-bottom: var(--spacing-sm); }
.mt-2 { margin-top: var(--spacing-md); }
.mb-2 { margin-bottom: var(--spacing-md); }
.mt-3 { margin-top: var(--spacing-lg); }
.mb-3 { margin-bottom: var(--spacing-lg); }

.d-none { display: none !important; }
.d-block { display: block !important; }
.d-flex { display: flex !important; }
.d-grid { display: grid !important; }

/* ============================================================================
   RESPONSIVE BREAKPOINTS
   ============================================================================ */

/* Large Tablets & Small Desktops (max-width: 1024px) */
@media (max-width: 1024px) {
    :root {
        --font-size-4xl: 2rem;
        --font-size-3xl: 1.75rem;
        --spacing-3xl: 3rem;
    }

    .content-area {
        padding: var(--spacing-xl);
    }
}

/* Tablets (max-width: 768px) */
@media (max-width: 768px) {
    :root {
        --font-size-4xl: 1.75rem;
        --font-size-3xl: 1.5rem;
        --font-size-2xl: 1.25rem;
    }

    .container {
        padding: 0 var(--spacing-md);
    }

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

    .stat-item {
        flex-direction: column;
        text-align: center;
    }

    .circuit-simulator {
        grid-template-columns: 1fr;
    }

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

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

    .back-to-top {
        bottom: 20px;
        right: 20px;
        width: 45px;
        height: 45px;
    }
}

/* Mobile (max-width: 640px) */
@media (max-width: 640px) {
    :root {
        --font-size-4xl: 1.5rem;
        --font-size-3xl: 1.25rem;
        --spacing-2xl: 2rem;
    }

    .content-area {
        padding: var(--spacing-md);
    }

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

    .article-meta {
        flex-direction: column;
        align-items: flex-start;
    }

    .calc-result p {
        flex-direction: column;
        align-items: flex-start;
        gap: var(--spacing-xs);
    }
}

/* ============================================================================
   PRINT STYLES
   ============================================================================ */
@media print {
    .main-header,
    .sidebar,
    .nav-toggle,
    .back-to-top,
    .main-footer,
    .hero-cta,
    .btn {
        display: none !important;
    }

    .content-area {
        box-shadow: none;
    }

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

    * {
        color: #000 !important;
        background: #fff !important;
    }
}

/* ============================================================================
   ANIMATIONS & KEYFRAMES
   ============================================================================ */
@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes slideInLeft {
    from {
        opacity: 0;
        transform: translateX(-30px);
    }
    to {
        opacity: 1;
        transform: translateX(0);
    }
}

@keyframes slideInRight {
    from {
        opacity: 0;
        transform: translateX(30px);
    }
    to {
        opacity: 1;
        transform: translateX(0);
    }
}

.fade-in {
    animation: fadeIn 0.5s ease-out;
}

.slide-in-left {
    animation: slideInLeft 0.5s ease-out;
}

.slide-in-right {
    animation: slideInRight 0.5s ease-out;
}

/* ============================================================================
   ACCESSIBILITY ENHANCEMENTS
   ============================================================================ */
:focus-visible {
    outline: 2px solid var(--primary-color);
    outline-offset: 2px;
}

.sr-only {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    white-space: nowrap;
    border-width: 0;
}

/* Reduced Motion */
@media (prefers-reduced-motion: reduce) {
    *,
    *::before,
    *::after {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
    }
}

/* ============================================================================
   CALCULATOR ENHANCEMENTS
   ============================================================================ */

.calculator-section {
    background: white;
    border-radius: var(--radius-lg);
    padding: var(--spacing-xl);
    margin: var(--spacing-xl) 0;
    box-shadow: var(--shadow-md);
}

.calculator-panel {
    margin-top: var(--spacing-lg);
}

.calc-tabs {
    display: flex;
    gap: var(--spacing-sm);
    margin-bottom: var(--spacing-lg);
    border-bottom: 2px solid var(--border-color);
}

.calc-tab {
    padding: var(--spacing-sm) var(--spacing-lg);
    background: transparent;
    border: none;
    border-bottom: 3px solid transparent;
    cursor: pointer;
    font-size: var(--font-size-base);
    font-weight: 500;
    color: var(--text-secondary);
    transition: all var(--transition-speed);
    position: relative;
    top: 2px;
}

.calc-tab:hover {
    color: var(--primary-color);
    background: var(--bg-secondary);
}

.calc-tab.active {
    color: var(--primary-color);
    border-bottom-color: var(--primary-color);
    font-weight: 600;
}

.calc-body {
    background: var(--bg-secondary);
    border-radius: var(--radius-md);
    padding: var(--spacing-xl);
}

.calc-inputs {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: var(--spacing-lg);
    margin-bottom: var(--spacing-lg);
}

.calc-input-group {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-sm);
}

.calc-input-group label {
    font-weight: 600;
    color: var(--text-primary);
    font-size: var(--font-size-sm);
}

.calc-input-group input,
.calc-input-group select {
    padding: var(--spacing-sm) var(--spacing-md);
    border: 2px solid var(--border-color);
    border-radius: var(--radius-sm);
    font-size: var(--font-size-base);
    transition: border-color var(--transition-speed);
    background: white;
}

.calc-input-group input:focus,
.calc-input-group select:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(33, 150, 243, 0.1);
}

.calc-input-group small {
    color: var(--text-secondary);
    font-size: var(--font-size-xs);
    margin-top: calc(var(--spacing-xs) * -1);
}

.calc-result {
    background: linear-gradient(135deg, #E8F5E9, #E3F2FD);
    border-left: 4px solid var(--success-color);
    border-radius: var(--radius-md);
    padding: var(--spacing-lg);
    margin: var(--spacing-lg) 0;
}

.calc-result h5 {
    color: var(--success-color);
    margin-bottom: var(--spacing-md);
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
}

.calc-result p {
    margin: var(--spacing-sm) 0;
    font-size: var(--font-size-base);
}

.calc-result strong {
    color: var(--text-primary);
    font-weight: 600;
}

.calc-result .note {
    font-size: var(--font-size-sm);
    color: var(--text-secondary);
    font-style: italic;
    margin-top: var(--spacing-md);
    padding-top: var(--spacing-md);
    border-top: 1px solid rgba(0, 0, 0, 0.1);
}

.calc-result .recommendation {
    background: rgba(255, 152, 0, 0.1);
    border-left: 3px solid var(--warning-color);
    padding: var(--spacing-sm) var(--spacing-md);
    margin-top: var(--spacing-md);
    border-radius: var(--radius-sm);
    font-size: var(--font-size-sm);
}

.calc-info {
    background: var(--bg-light);
    border-radius: var(--radius-md);
    padding: var(--spacing-lg);
    margin-top: var(--spacing-xl);
}

.calc-info h5 {
    color: var(--primary-color);
    margin-bottom: var(--spacing-md);
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
}

.calc-info ul {
    margin: var(--spacing-sm) 0;
    padding-left: var(--spacing-lg);
}

.calc-info li {
    margin: var(--spacing-sm) 0;
    line-height: 1.6;
}

/* Calculator Button Styles */
.calculator-panel .btn-primary {
    width: 100%;
    padding: var(--spacing-md) var(--spacing-xl);
    font-size: var(--font-size-lg);
    font-weight: 600;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: var(--spacing-sm);
}

/* Responsive Calculator Layout */
@media (max-width: 768px) {
    .calc-inputs {
        grid-template-columns: 1fr;
    }

    .calc-tabs {
        flex-direction: column;
        border-bottom: none;
    }

    .calc-tab {
        border-bottom: none;
        border-left: 3px solid transparent;
        top: 0;
        left: 0;
    }

    .calc-tab.active {
        border-left-color: var(--primary-color);
        border-bottom-color: transparent;
    }
}

/* ============================================================================
   END OF STYLES
   ============================================================================ */
/* ============================================================================
   NAVIGATION ACTIONS (SEARCH & THEME TOGGLE)
   ============================================================================ */

.nav-actions {
    display: flex;
    align-items: center;
    gap: 12px;
    margin-left: auto;
}

.search-toggle, .theme-toggle {
    width: 40px;
    height: 40px;
    border-radius: 50%;
    border: none;
    background: #f5f7fa;
    color: #666;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all 0.3s;
}

.search-toggle:hover, .theme-toggle:hover {
    background: #2196F3;
    color: white;
    transform: scale(1.1);
}

/* ============================================================================
   SEARCH MODAL
   ============================================================================ */

.search-modal {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.7);
    backdrop-filter: blur(4px);
    z-index: 10000;
    display: none;
    align-items: flex-start;
    justify-content: center;
    padding: 80px 20px;
}

.search-modal.active { display: flex; }

.search-modal-content {
    width: 100%;
    max-width: 680px;
    background: white;
    border-radius: 12px;
    box-shadow: 0 20px 60px rgba(0,0,0,0.3);
    max-height: calc(100vh - 160px);
    display: flex;
    flex-direction: column;
}

.search-header {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 20px;
    border-bottom: 1px solid #e0e0e0;
}

.search-input-wrapper {
    flex: 1;
    display: flex;
    align-items: center;
    gap: 10px;
}

#searchInput {
    flex: 1;
    border: none;
    outline: none;
    font-size: 18px;
    padding: 8px 0;
}

.search-clear, .search-close {
    width: 32px;
    height: 32px;
    border-radius: 50%;
    border: none;
    background: #f5f7fa;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
}

.search-shortcuts {
    display: flex;
    gap: 12px;
    padding: 8px 20px;
    background: #f5f7fa;
    font-size: 14px;
}

.shortcut-tip kbd {
    padding: 2px 6px;
    background: white;
    border: 1px solid #ddd;
    border-radius: 3px;
    font-family: monospace;
    font-size: 11px;
}

.search-results {
    flex: 1;
    overflow-y: auto;
    padding: 20px;
}

.search-result-item {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 12px;
    background: #f5f7fa;
    border-radius: 8px;
    cursor: pointer;
    margin-bottom: 8px;
    transition: all 0.3s;
}

.search-result-item:hover {
    background: #2196F3;
    color: white;
    transform: translateX(4px);
}

.result-icon {
    width: 40px;
    height: 40px;
    border-radius: 50%;
    background: white;
    display: flex;
    align-items: center;
    justify-content: center;
}

.result-content { flex: 1; }

.result-title { font-weight: 600; margin-bottom: 4px; }

.result-snippet {
    font-size: 14px;
    color: #666;
    overflow: hidden;
    text-overflow: ellipsis;
}

.suggestion-tag {
    padding: 6px 12px;
    background: #f5f7fa;
    border-radius: 20px;
    font-size: 14px;
    cursor: pointer;
    display: inline-block;
    margin: 4px;
    transition: all 0.3s;
}

.suggestion-tag:hover {
    background: #2196F3;
    color: white;
}

/* ============================================================================
   DARK MODE
   ============================================================================ */

[data-theme="dark"] {
    --bg-primary: #1a1a1a;
    --bg-secondary: #2d2d2d;
    --text-primary: #e0e0e0;
    --text-secondary: #a0a0a0;
}

[data-theme="dark"] body {
    background: #1a1a1a;
    color: #e0e0e0;
}

[data-theme="dark"] .search-modal-content {
    background: #1a1a1a;
}

[data-theme="dark"] .search-result-item {
    background: #2d2d2d;
}

[data-theme="dark"] #searchInput {
    color: #e0e0e0;
}


/* ===== 学习路径指引样式 ===== */
.learning-path {
    padding: 80px 0;
    background: linear-gradient(135deg, #f5f7fa 0%, #c3cfe2 100%);
}

[data-theme="dark"] .learning-path {
    background: linear-gradient(135deg, #2d2d2d 0%, #1a1a1a 100%);
}

.learning-path .section-subtitle {
    text-align: center;
    color: var(--text-secondary);
    font-size: 1.1rem;
    margin-bottom: 50px;
}

.path-options {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
    gap: 30px;
    margin-bottom: 60px;
}

.path-card {
    background: white;
    border-radius: var(--radius-lg);
    padding: 30px;
    box-shadow: var(--shadow-lg);
    transition: transform 0.3s, box-shadow 0.3s;
}

[data-theme="dark"] .path-card {
    background: var(--bg-secondary);
}

.path-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 10px 40px rgba(0,0,0,0.15);
}

.path-header {
    text-align: center;
    margin-bottom: 20px;
}

.path-icon {
    width: 80px;
    height: 80px;
    margin: 0 auto 15px;
    background: linear-gradient(135deg, var(--primary-color), var(--accent-color));
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 2.5rem;
    color: white;
}

.path-card.beginner .path-icon {
    background: linear-gradient(135deg, #4CAF50, #81C784);
}

.path-card.intermediate-path .path-icon {
    background: linear-gradient(135deg, #2196F3, #64B5F6);
}

.path-card.advanced-path .path-icon {
    background: linear-gradient(135deg, #9C27B0, #BA68C8);
}

.path-header h3 {
    font-size: 1.5rem;
    margin: 10px 0 5px;
}

.path-badge {
    display: inline-block;
    padding: 4px 12px;
    background: var(--primary-color);
    color: white;
    border-radius: 20px;
    font-size: 0.85rem;
    font-weight: 500;
}

.path-description {
    color: var(--text-secondary);
    text-align: center;
    margin-bottom: 25px;
    line-height: 1.6;
}

.path-timeline {
    margin: 25px 0;
}

.timeline-item {
    display: flex;
    gap: 15px;
    margin-bottom: 20px;
    position: relative;
}

.timeline-item:not(:last-child)::after {
    content: '';
    position: absolute;
    left: 14px;
    top: 35px;
    width: 2px;
    height: calc(100% + 5px);
    background: linear-gradient(180deg, var(--primary-color), transparent);
}

.timeline-marker {
    width: 30px;
    height: 30px;
    background: var(--primary-color);
    color: white;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: bold;
    font-size: 0.9rem;
    flex-shrink: 0;
}

.timeline-content {
    flex: 1;
}

.timeline-content h4 {
    margin: 0 0 5px;
    font-size: 1rem;
}

.timeline-content h4 a {
    color: var(--primary-color);
    text-decoration: none;
    transition: color 0.3s;
}

.timeline-content h4 a:hover {
    color: var(--accent-color);
    text-decoration: underline;
}

.timeline-content p {
    margin: 5px 0;
    font-size: 0.9rem;
    color: var(--text-secondary);
}

.duration {
    display: inline-block;
    font-size: 0.85rem;
    color: var(--text-secondary);
    margin-top: 5px;
}

.duration i {
    margin-right: 4px;
}

.path-footer {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-top: 25px;
    padding-top: 20px;
    border-top: 1px solid var(--border-color);
}

.estimated-time {
    font-size: 0.9rem;
    color: var(--text-secondary);
    font-weight: 500;
}

/* 学习建议 */
.learning-tips {
    background: white;
    border-radius: var(--radius-lg);
    padding: 40px;
    box-shadow: var(--shadow-md);
}

[data-theme="dark"] .learning-tips {
    background: var(--bg-secondary);
}

.learning-tips h3 {
    text-align: center;
    margin-bottom: 30px;
    font-size: 1.8rem;
}

.learning-tips h3 i {
    color: var(--accent-color);
    margin-right: 10px;
}

.tips-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 25px;
}

.tip-card {
    text-align: center;
    padding: 20px;
    border-radius: var(--radius-md);
    background: var(--bg-primary);
    border: 2px solid var(--border-color);
    transition: all 0.3s;
}

[data-theme="dark"] .tip-card {
    background: #1a1a1a;
}

.tip-card:hover {
    border-color: var(--primary-color);
    transform: translateY(-3px);
    box-shadow: var(--shadow-md);
}

.tip-card i {
    font-size: 2.5rem;
    color: var(--primary-color);
    margin-bottom: 15px;
    display: block;
}

.tip-card h4 {
    margin: 10px 0;
    font-size: 1.1rem;
}

.tip-card p {
    color: var(--text-secondary);
    font-size: 0.9rem;
    line-height: 1.5;
    margin: 0;
}

/* 响应式 */
@media (max-width: 768px) {
    .path-options {
        grid-template-columns: 1fr;
    }
    
    .learning-path {
        padding: 50px 0;
    }
    
    .learning-tips {
        padding: 25px;
    }
    
    .tips-grid {
        grid-template-columns: 1fr;
        gap: 15px;
    }
    
    .path-footer {
        flex-direction: column;
        gap: 15px;
    }
}

/* ===== 案例库页面样式 ===== */
.cases-hero {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    padding: 100px 0 60px;
    text-align: center;
}

[data-theme="dark"] .cases-hero {
    background: linear-gradient(135deg, #434343 0%, #000000 100%);
}

.cases-hero h1 {
    font-size: 2.5rem;
    margin-bottom: 15px;
}

.cases-hero .hero-subtitle {
    font-size: 1.2rem;
    opacity: 0.9;
    margin-bottom: 30px;
}

.cases-stats {
    display: flex;
    justify-content: center;
    gap: 60px;
    margin-top: 40px;
}

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

.cases-stats .stat-item strong {
    display: block;
    font-size: 2.5rem;
    font-weight: 700;
    margin-bottom: 5px;
}

.cases-stats .stat-item span {
    font-size: 1rem;
    opacity: 0.9;
}

/* 分类导航 */
.case-categories {
    padding: 60px 0;
    background: var(--bg-primary);
}

.category-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
    gap: 20px;
    margin-top: 30px;
}

.category-card {
    background: white;
    padding: 25px 15px;
    border-radius: var(--radius-md);
    text-align: center;
    cursor: pointer;
    transition: all 0.3s;
    border: 2px solid transparent;
}

[data-theme="dark"] .category-card {
    background: var(--bg-secondary);
}

.category-card:hover,
.category-card.active {
    border-color: var(--primary-color);
    transform: translateY(-5px);
    box-shadow: var(--shadow-lg);
}

.category-card i {
    font-size: 2.5rem;
    color: var(--primary-color);
    margin-bottom: 10px;
}

.category-card h3 {
    font-size: 1rem;
    margin: 10px 0 5px;
}

.category-card .case-count {
    display: inline-block;
    padding: 4px 12px;
    background: var(--primary-color);
    color: white;
    border-radius: 20px;
    font-size: 0.85rem;
    font-weight: 600;
}

/* 案例列表 */
.cases-list {
    padding: 60px 0;
    background: var(--bg-secondary);
}

[data-theme="dark"] .cases-list {
    background: #1a1a1a;
}

.cases-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 40px;
    flex-wrap: wrap;
    gap: 20px;
}

.filter-controls {
    display: flex;
    gap: 15px;
}

.filter-controls select {
    padding: 10px 15px;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-sm);
    background: white;
    color: var(--text-primary);
    font-size: 0.95rem;
    cursor: pointer;
    transition: border-color 0.3s;
}

[data-theme="dark"] .filter-controls select {
    background: var(--bg-secondary);
    color: var(--text-primary);
}

.filter-controls select:hover {
    border-color: var(--primary-color);
}

.filter-controls select:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(33, 150, 243, 0.1);
}

/* 案例卡片网格 */
.cases-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(350px, 1fr));
    gap: 30px;
}

.case-card {
    background: white;
    border-radius: var(--radius-lg);
    overflow: hidden;
    box-shadow: var(--shadow-md);
    transition: all 0.3s;
    opacity: 1;
    transform: translateY(0);
}

[data-theme="dark"] .case-card {
    background: var(--bg-secondary);
}

.case-card:hover {
    box-shadow: var(--shadow-lg);
}

.case-image {
    position: relative;
    height: 180px;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    display: flex;
    align-items: center;
    justify-content: center;
}

.case-badge {
    position: absolute;
    top: 15px;
    right: 15px;
    padding: 6px 14px;
    border-radius: 20px;
    font-size: 0.85rem;
    font-weight: 600;
    color: white;
}

.case-badge.beginner {
    background: #4CAF50;
}

.case-badge.intermediate {
    background: #2196F3;
}

.case-badge.advanced {
    background: #9C27B0;
}

.case-icon {
    font-size: 4rem;
    color: white;
    opacity: 0.3;
}

.case-content {
    padding: 25px;
}

.case-content h3 {
    margin: 0 0 12px;
    font-size: 1.3rem;
    line-height: 1.4;
}

.case-description {
    color: var(--text-secondary);
    line-height: 1.6;
    margin-bottom: 15px;
    font-size: 0.95rem;
}

.case-tags {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
    margin-bottom: 15px;
}

.case-tags .tag {
    padding: 4px 10px;
    background: var(--bg-primary);
    color: var(--text-secondary);
    border-radius: 4px;
    font-size: 0.85rem;
    border: 1px solid var(--border-color);
}

[data-theme="dark"] .case-tags .tag {
    background: #1a1a1a;
}

.case-meta {
    display: flex;
    gap: 15px;
    margin-bottom: 15px;
    font-size: 0.9rem;
    color: var(--text-secondary);
    flex-wrap: wrap;
}

.case-meta span {
    display: flex;
    align-items: center;
    gap: 5px;
}

.case-specs {
    background: var(--bg-primary);
    padding: 15px;
    border-radius: var(--radius-sm);
    margin-bottom: 20px;
    border-left: 3px solid var(--primary-color);
}

[data-theme="dark"] .case-specs {
    background: #1a1a1a;
}

.case-specs p {
    margin: 8px 0;
    font-size: 0.9rem;
    line-height: 1.5;
}

.case-specs strong {
    color: var(--primary-color);
    display: inline-block;
    min-width: 80px;
}

.case-card .btn {
    width: 100%;
}

/* Coming soon card */
.case-card.coming-soon {
    border: 2px dashed var(--border-color);
    background: var(--bg-primary);
}

[data-theme="dark"] .case-card.coming-soon {
    background: #1a1a1a;
}

.case-card.coming-soon .case-image {
    background: linear-gradient(135deg, #E0E0E0 0%, #BDBDBD 100%);
}

[data-theme="dark"] .case-card.coming-soon .case-image {
    background: linear-gradient(135deg, #424242 0%, #212121 100%);
}

.case-card.coming-soon .case-icon {
    opacity: 0.5;
}

/* 案例提交区域 */
.submit-case {
    padding: 80px 0;
    background: linear-gradient(135deg, #f5f7fa 0%, #c3cfe2 100%);
    text-align: center;
}

[data-theme="dark"] .submit-case {
    background: linear-gradient(135deg, #2d2d2d 0%, #1a1a1a 100%);
}

.submit-case h2 {
    margin-bottom: 15px;
}

.submit-case p {
    font-size: 1.1rem;
    color: var(--text-secondary);
    margin-bottom: 30px;
}

/* 响应式 */
@media (max-width: 768px) {
    .cases-hero {
        padding: 80px 0 40px;
    }

    .cases-hero h1 {
        font-size: 2rem;
    }

    .cases-stats {
        gap: 30px;
    }

    .cases-stats .stat-item strong {
        font-size: 2rem;
    }

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

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

    .cases-header {
        flex-direction: column;
        align-items: flex-start;
    }

    .filter-controls {
        width: 100%;
        flex-direction: column;
    }

    .filter-controls select {
        width: 100%;
    }
}

@media (max-width: 480px) {
    .category-grid {
        grid-template-columns: 1fr;
    }

    .cases-stats {
        flex-direction: column;
        gap: 20px;
    }
}

/* ============================================================================
   SMART TOC NAVIGATION - HIGHLIGHT EFFECT
   智能目录导航 - 高亮效果
   ============================================================================ */

/* 目标标题高亮动画 */
.toc-highlight {
    animation: tocHighlight 2s ease-in-out;
    position: relative;
}

/* 高亮动画：闪烁背景（增强版，更明显） */
@keyframes tocHighlight {
    0% {
        background-color: transparent;
        transform: scale(1);
        box-shadow: none;
    }
    5% {
        background-color: rgba(33, 150, 243, 0.3);
        transform: scale(1.03);
        box-shadow: 0 0 20px rgba(33, 150, 243, 0.3);
    }
    15% {
        background-color: rgba(33, 150, 243, 0.4);
        transform: scale(1.02);
        box-shadow: 0 0 25px rgba(33, 150, 243, 0.4);
    }
    30% {
        background-color: rgba(33, 150, 243, 0.25);
        box-shadow: 0 0 15px rgba(33, 150, 243, 0.2);
    }
    50% {
        background-color: rgba(33, 150, 243, 0.15);
        box-shadow: 0 0 10px rgba(33, 150, 243, 0.15);
    }
    70% {
        background-color: rgba(33, 150, 243, 0.10);
        box-shadow: 0 0 5px rgba(33, 150, 243, 0.1);
    }
    100% {
        background-color: transparent;
        transform: scale(1);
        box-shadow: none;
    }
}

/* 左侧边框指示器（增强版，更粗更明显） */
.toc-highlight::before {
    content: '';
    position: absolute;
    left: -20px;
    top: 0;
    bottom: 0;
    width: 6px;
    background: linear-gradient(180deg, var(--primary-color), var(--accent-color));
    border-radius: 3px;
    animation: highlightBorder 2s ease-in-out;
    box-shadow: 0 0 10px rgba(33, 150, 243, 0.5);
}

@keyframes highlightBorder {
    0%, 100% {
        opacity: 0;
        transform: scaleY(0);
        box-shadow: 0 0 0 rgba(33, 150, 243, 0);
    }
    5% {
        opacity: 1;
        transform: scaleY(1);
        box-shadow: 0 0 15px rgba(33, 150, 243, 0.6);
    }
    15% {
        box-shadow: 0 0 20px rgba(33, 150, 243, 0.7);
    }
    90% {
        opacity: 1;
        transform: scaleY(1);
        box-shadow: 0 0 10px rgba(33, 150, 243, 0.4);
    }
}

/* 响应式调整 */
@media (max-width: 768px) {
    .toc-highlight::before {
        left: -10px;
        width: 3px;
    }
}

/* 暗色模式适配 */
[data-theme="dark"] .toc-highlight {
    animation: tocHighlightDark 2s ease-in-out;
}

@keyframes tocHighlightDark {
    0% {
        background-color: transparent;
        box-shadow: none;
    }
    5% {
        background-color: rgba(33, 150, 243, 0.35);
        box-shadow: 0 0 25px rgba(33, 150, 243, 0.4);
    }
    15% {
        background-color: rgba(33, 150, 243, 0.45);
        box-shadow: 0 0 30px rgba(33, 150, 243, 0.5);
    }
    30% {
        background-color: rgba(33, 150, 243, 0.35);
        box-shadow: 0 0 20px rgba(33, 150, 243, 0.3);
    }
    50% {
        background-color: rgba(33, 150, 243, 0.25);
    }
    60% {
        background-color: rgba(33, 150, 243, 0.15);
    }
    100% {
        background-color: transparent;
    }
}