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

:root {
    /* Professional grayscale palette */
    --color-gray-900: #1a1a1a;
    --color-gray-800: #2d2d2d;
    --color-gray-700: #404040;
    --color-gray-600: #666666;
    --color-gray-500: #808080;
    --color-gray-400: #999999;
    --color-gray-300: #cccccc;
    --color-gray-200: #e5e5e5;
    --color-gray-100: #f5f5f5;
    --color-white: #ffffff;

    /* Accent color - used sparingly */
    --color-accent: #3b82f6;
    --color-accent-hover: #2563eb;

    /* Semantic colors */
    --text-primary: var(--color-gray-900);
    --text-secondary: var(--color-gray-600);
    --border-color: var(--color-gray-200);
    --bg-body: var(--color-white);
    --bg-section: var(--color-gray-100);
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Inter', 'SF Pro Display', 'Segoe UI', system-ui, sans-serif;
    line-height: 1.75;
    color: var(--text-primary);
    background-color: var(--bg-body);
    font-weight: 450;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

/* Header & Navigation */
header {
    background: var(--color-white);
    border-bottom: 1px solid var(--border-color);
    padding: 0;
    position: sticky;
    top: 0;
    z-index: 1000;
    box-shadow: 0 1px 3px rgba(0, 0, 0, 0.05);
}

nav {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 2rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
    height: 64px;
}

.logo {
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--text-primary);
    display: flex;
    align-items: center;
    gap: 0.5rem;
    letter-spacing: -0.02em;
    text-decoration: none;
}

.logo img {
    display: block;
    border-radius: 6px;
    transition: transform 0.2s ease;
}

.logo:hover img {
    transform: scale(1.05);
}

.nav-links {
    display: flex;
    gap: 0;
    list-style: none;
    height: 100%;
    align-items: center;
}

.nav-links li {
    height: 100%;
    display: flex;
    align-items: center;
}

.nav-links a {
    color: var(--text-secondary);
    text-decoration: none;
    font-weight: 600;
    font-size: 0.9rem;
    padding: 0 1.25rem;
    height: 100%;
    display: flex;
    align-items: center;
    transition: color 0.2s ease, background-color 0.2s ease;
    border-bottom: 2px solid transparent;
}

.nav-links a:hover {
    color: var(--text-primary);
    background-color: var(--bg-section);
}

.nav-links a:active,
.nav-links a:focus,
.nav-links a.active {
    color: var(--text-primary);
    border-bottom-color: var(--color-accent);
}

/* Hero Section */
.hero {
    background: var(--color-white);
    border-bottom: 1px solid var(--border-color);
    padding: 5rem 2rem 4rem;
    text-align: center;
}

.hero h1 {
    font-size: 3.5rem;
    margin-bottom: 1.5rem;
    font-weight: 800;
    color: var(--text-primary);
    letter-spacing: -0.03em;
    line-height: 1.1;
}

.hero p {
    font-size: 1.15rem;
    max-width: 700px;
    margin: 0 auto;
    color: var(--text-secondary);
    font-weight: 500;
    line-height: 1.6;
}

.hero p strong {
    color: var(--text-primary);
    font-weight: 700;
}

.hero-subtitle {
    font-size: 1.1rem;
    opacity: 0.9;
    max-width: 900px;
    margin: 0 auto;
}

/* Main Content */
.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 4rem 2rem;
    background: var(--bg-section);
}

.content-section {
    background: var(--color-white);
    border-radius: 0;
    padding: 4rem 3rem;
    margin-bottom: 3rem;
    border: 1px solid var(--border-color);
}

h2 {
    font-size: 2.5rem;
    margin-bottom: 2rem;
    color: var(--text-primary);
    font-weight: 800;
    letter-spacing: -0.02em;
    border-bottom: 2px solid var(--color-gray-200);
    padding-bottom: 1rem;
}

h3 {
    font-size: 1.75rem;
    margin: 3rem 0 1.5rem;
    color: var(--text-primary);
    font-weight: 700;
    letter-spacing: -0.01em;
}

h4 {
    font-size: 1.25rem;
    margin: 2rem 0 1rem;
    color: var(--text-primary);
    font-weight: 700;
}

p {
    margin-bottom: 1.25rem;
    line-height: 1.75;
    color: var(--text-secondary);
    font-weight: 450;
}

strong {
    color: var(--text-primary);
    font-weight: 700;
}

/* Lists */
ul, ol {
    margin: 1rem 0 1rem 2rem;
    color: var(--text-secondary);
}

li {
    margin-bottom: 0.5rem;
    line-height: 1.7;
}

/* Tables */
table {
    width: 100%;
    border-collapse: collapse;
    margin: 2rem 0;
    background: var(--color-white);
    border: 1px solid var(--border-color);
}

th, td {
    padding: 1rem 1.25rem;
    text-align: left;
    border-bottom: 1px solid var(--border-color);
}

th {
    background: var(--bg-section);
    font-weight: 700;
    color: var(--text-primary);
    font-size: 0.9rem;
}

td {
    font-size: 0.95rem;
}

tr:last-child td {
    border-bottom: none;
}

tr:hover td {
    background: var(--bg-section);
}

/* Info Boxes */
.highlight-box,
.warning-box,
.success-box,
.danger-box {
    background: var(--bg-section);
    border: 1px solid var(--border-color);
    border-left: 3px solid var(--color-gray-600);
    padding: 2rem;
    margin: 2rem 0;
    border-radius: 0;
}

.warning-box {
    border-left-color: var(--color-gray-700);
}

.success-box {
    border-left-color: var(--color-gray-800);
}

.danger-box {
    border-left-color: var(--color-gray-900);
}

.highlight-box h4,
.warning-box h4,
.success-box h4,
.danger-box h4 {
    margin-top: 0;
    font-size: 1.1rem;
    font-weight: 700;
    color: var(--text-primary);
}

/* Feature Grid */
.feature-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 1.5rem;
    margin: 2.5rem 0;
}

.feature-card {
    background: var(--bg-section);
    padding: 2rem;
    border-radius: 0;
    border: 1px solid var(--border-color);
    transition: border-color 0.2s ease;
}

.feature-card:hover {
    border-color: var(--color-gray-400);
}

.feature-card h4 {
    margin-top: 0;
    margin-bottom: 0.75rem;
    color: var(--text-primary);
    font-size: 1.1rem;
    font-weight: 700;
}

.feature-card p {
    margin: 0;
    font-size: 0.95rem;
}

/* Guide Cards (for homepage) */
.guide-cards-section {
    background: var(--color-white);
    padding: 4rem 0;
}

.guide-cards {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 2rem;
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 2rem;
}

.guide-card {
    background: var(--color-white);
    border: 2px solid var(--border-color);
    padding: 2.5rem;
    text-decoration: none;
    color: inherit;
    transition: all 0.3s ease;
    display: block;
}

.guide-card:hover {
    transform: translateY(-4px);
    border-color: var(--color-gray-400);
    box-shadow: 0 8px 24px rgba(0, 0, 0, 0.1);
}

.guide-card h3 {
    margin: 0 0 1rem 0;
    font-size: 1.5rem;
    color: var(--text-primary);
}

.guide-card p {
    margin: 0 0 1.5rem 0;
    color: var(--text-secondary);
    font-size: 1rem;
}

.guide-card .read-more {
    color: var(--color-accent);
    font-weight: 600;
    font-size: 0.95rem;
}

.guide-card:hover .read-more {
    color: var(--color-accent-hover);
}

/* Breadcrumbs */
.breadcrumbs {
    max-width: 1200px;
    margin: 0 auto;
    padding: 1rem 2rem;
    background: var(--bg-section);
}

.breadcrumbs ol {
    list-style: none;
    display: flex;
    gap: 0.5rem;
    margin: 0;
    padding: 0;
    font-size: 0.9rem;
}

.breadcrumbs li::after {
    content: "/";
    margin-left: 0.5rem;
    color: var(--color-gray-400);
}

.breadcrumbs li:last-child::after {
    content: "";
}

.breadcrumbs a {
    color: var(--color-accent);
    text-decoration: none;
}

.breadcrumbs a:hover {
    text-decoration: underline;
}

.breadcrumbs li[aria-current="page"] {
    color: var(--text-secondary);
}

/* Code blocks */
code {
    background: var(--bg-section);
    padding: 0.2rem 0.5rem;
    border-radius: 3px;
    font-family: 'SF Mono', 'Monaco', 'Consolas', monospace;
    font-size: 0.875rem;
    color: var(--text-primary);
    border: 1px solid var(--border-color);
}

pre {
    background: var(--bg-section);
    padding: 1.5rem;
    border-radius: 8px;
    overflow-x: auto;
    margin: 1rem 0;
    border: 1px solid var(--border-color);
}

pre code {
    background: none;
    padding: 0;
    border: none;
}

/* Links */
a {
    color: var(--color-accent);
    text-decoration: none;
    transition: color 0.2s;
}

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

/* Table of Contents */
.toc {
    background: var(--color-white);
    padding: 2.5rem;
    border-radius: 0;
    margin-bottom: 3rem;
    border: 1px solid var(--border-color);
}

.toc h3 {
    margin-top: 0;
    margin-bottom: 1.5rem;
    color: var(--text-primary);
    font-weight: 700;
    font-size: 1.25rem;
}

.toc ul {
    list-style: none;
    margin-left: 0;
}

.toc li {
    margin-bottom: 0;
    border-bottom: 1px solid var(--border-color);
}

.toc li:last-child {
    border-bottom: none;
}

.toc a {
    color: var(--text-secondary);
    display: block;
    padding: 0.875rem 0;
    border-radius: 0;
    transition: color 0.2s ease;
    font-weight: 600;
    font-size: 0.95rem;
}

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

/* Footer */
footer {
    background: var(--color-gray-900);
    color: var(--color-gray-300);
    padding: 3rem 2rem;
    margin-top: 0;
    border-top: 1px solid var(--border-color);
}

.footer-content {
    max-width: 1200px;
    margin: 0 auto;
    text-align: center;
}

.footer-links {
    display: flex;
    justify-content: center;
    gap: 2rem;
    margin-bottom: 1rem;
    flex-wrap: wrap;
}

.footer-links a {
    color: var(--color-gray-400);
    font-weight: 600;
    font-size: 0.9rem;
}

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

/* Mobile Menu Toggle */
.mobile-menu-toggle {
    display: none;
    background: none;
    border: none;
    font-size: 1.5rem;
    color: var(--text-primary);
    cursor: pointer;
    padding: 0.5rem;
    z-index: 1001;
}

/* Responsive */
@media (max-width: 768px) {
    nav {
        padding: 0 1rem;
        height: 56px;
    }

    .logo {
        font-size: 1.1rem;
    }

    /* Mobile menu toggle button */
    .mobile-menu-toggle {
        display: block;
    }

    /* Hide nav links by default on mobile */
    .nav-links {
        position: fixed;
        top: 56px;
        left: 0;
        right: 0;
        background: var(--color-white);
        flex-direction: column;
        gap: 0;
        height: auto;
        align-items: stretch;
        border-bottom: 1px solid var(--border-color);
        box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
        max-height: 0;
        overflow: hidden;
        transition: max-height 0.3s ease;
    }

    .nav-links.active {
        max-height: 400px;
    }

    .nav-links li {
        height: auto;
        border-bottom: 1px solid var(--border-color);
    }

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

    .nav-links a {
        padding: 1rem 1.5rem;
        height: auto;
        border-bottom: none;
        justify-content: flex-start;
    }

    .nav-links a:hover {
        background-color: var(--bg-section);
    }

    /* Hero section */
    .hero {
        padding: 3rem 1.5rem 2.5rem;
    }

    .hero h1 {
        font-size: 2rem;
        line-height: 1.2;
    }

    .hero p {
        font-size: 1rem;
        margin-top: 1rem;
    }

    /* Content sections */
    .content-section {
        padding: 2rem 1.5rem;
    }

    .container {
        padding: 2rem 1rem;
    }

    h2 {
        font-size: 1.75rem;
        margin-bottom: 1.5rem;
    }

    h3 {
        font-size: 1.35rem;
        margin-top: 2rem;
        margin-bottom: 1rem;
    }

    /* Table responsiveness */
    .table-wrapper {
        overflow-x: auto;
        -webkit-overflow-scrolling: touch;
        margin: 1.5rem 0;
    }

    table {
        font-size: 0.85rem;
        min-width: 100%;
    }

    th, td {
        padding: 0.75rem 0.5rem;
        white-space: nowrap;
    }

    /* Lists */
    ul, ol {
        padding-left: 1.5rem;
    }

    li {
        margin-bottom: 0.75rem;
    }

    /* Scroll to top button */
    .scroll-top {
        width: 44px;
        height: 44px;
        bottom: 1rem;
        right: 1rem;
    }

    /* Footer */
    footer {
        padding: 2rem 1.5rem;
    }

    .footer-links {
        flex-direction: column;
        gap: 1rem;
        margin-bottom: 1.5rem;
    }

    /* Badges */
    .badge {
        font-size: 0.75rem;
        padding: 0.35rem 0.7rem;
        margin-right: 0.5rem;
        margin-bottom: 0.5rem;
        display: inline-block;
    }

    /* Code blocks */
    pre {
        font-size: 0.85rem;
        padding: 1rem;
        overflow-x: auto;
        -webkit-overflow-scrolling: touch;
    }

    /* Guide cards */
    .guide-cards {
        grid-template-columns: 1fr;
        gap: 1.5rem;
        padding: 0 1.5rem;
    }

    .guide-card {
        padding: 2rem;
    }
}

/* Tablet adjustments */
@media (max-width: 1024px) and (min-width: 769px) {
    nav {
        padding: 0 1.5rem;
    }

    .hero {
        padding: 4rem 2rem 3rem;
    }

    .hero h1 {
        font-size: 2.75rem;
    }

    .content-section {
        padding: 3rem 1.5rem;
    }
}

/* Scroll to top button */
.scroll-top {
    position: fixed;
    bottom: 2rem;
    right: 2rem;
    background: var(--color-gray-900);
    color: var(--color-white);
    width: 48px;
    height: 48px;
    border-radius: 0;
    display: flex;
    align-items: center;
    justify-content: center;
    border: 1px solid var(--color-gray-700);
    cursor: pointer;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.2);
    transition: transform 0.3s, opacity 0.3s;
    opacity: 0;
    pointer-events: none;
}

.scroll-top.visible {
    opacity: 1;
    pointer-events: auto;
}

.scroll-top:hover {
    transform: translateY(-4px);
}

/* Performance badges */
.badge {
    display: inline-block;
    padding: 0.4rem 0.85rem;
    border-radius: 0;
    font-size: 0.8rem;
    font-weight: 700;
    margin-right: 0.75rem;
    letter-spacing: 0.02em;
    text-transform: uppercase;
    border: 1px solid var(--border-color);
}

.badge-excellent {
    background: var(--bg-section);
    color: var(--text-primary);
}

.badge-good {
    background: var(--bg-section);
    color: var(--text-primary);
}

.badge-mixed {
    background: var(--bg-section);
    color: var(--text-primary);
}

.badge-poor {
    background: var(--bg-section);
    color: var(--text-primary);
}

/* Articles System */
.intro-text {
    font-size: 1.125rem;
    color: var(--text-secondary);
    margin-bottom: 2.5rem;
    line-height: 1.6;
}

.articles-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
    gap: 2rem;
    margin-top: 2rem;
}

.article-card {
    background: var(--color-white);
    border: 2px solid var(--border-color);
    padding: 2rem;
    transition: all 0.3s ease;
    display: flex;
    flex-direction: column;
}

.article-card:hover {
    transform: translateY(-4px);
    border-color: var(--color-gray-400);
    box-shadow: 0 8px 24px rgba(0, 0, 0, 0.1);
}

.article-meta {
    display: flex;
    gap: 1rem;
    margin-bottom: 1rem;
    font-size: 0.875rem;
}

.article-date {
    color: var(--text-secondary);
}

.article-category {
    background: var(--bg-section);
    color: var(--text-primary);
    padding: 0.25rem 0.75rem;
    border-radius: 3px;
    font-weight: 600;
    border: 1px solid var(--border-color);
}

.article-card h2 {
    margin: 0 0 1rem 0;
    font-size: 1.375rem;
    color: var(--text-primary);
    line-height: 1.3;
}

.article-card p {
    color: var(--text-secondary);
    margin-bottom: 1.5rem;
    line-height: 1.6;
    flex-grow: 1;
}

.article-link {
    color: var(--color-accent);
    font-weight: 600;
    text-decoration: none;
    display: inline-flex;
    align-items: center;
    transition: all 0.2s;
}

.article-link:hover {
    color: var(--color-accent-hover);
    transform: translateX(4px);
}

.info-box {
    background: var(--bg-section);
    border: 2px solid var(--border-color);
    padding: 2rem;
    border-radius: 0;
}

.info-box h3 {
    margin-top: 0;
    color: var(--text-primary);
}

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

/* Article Header */
.article-header {
    margin-bottom: 2.5rem;
}

.article-header h1 {
    font-size: 2.5rem;
    line-height: 1.2;
    margin: 1rem 0;
}

.article-footer {
    margin-top: 3rem;
    padding-top: 2rem;
    border-top: 2px solid var(--border-color);
}

@media (max-width: 768px) {
    .article-header h1 {
        font-size: 1.875rem;
    }

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