/* ============================================
   TECHNICAL BLOG DESIGN SYSTEM
   Theme: Dark-first, modern technical blog
   Font: Inter (Google Fonts loaded in layout)
   ============================================ */

/* --- CSS Custom Properties --- */
:root {
    /* Colors - Dark Mode (default) */
    --bg-primary: #0f1117;
    --bg-secondary: #161822;
    --bg-card: #1c1f2e;
    --bg-card-hover: #232738;
    --bg-code: #1a1d2e;
    --bg-nav: rgba(15, 17, 23, 0.85);
    --text-primary: #e4e6f0;
    --text-secondary: #9ca3b8;
    --text-muted: #6b7394;
    --accent: #22d3ee;
    --accent-secondary: #06b6d4;
    --accent-gradient: linear-gradient(135deg, #22d3ee, #0ea5e9);
    --border-color: rgba(255, 255, 255, 0.06);
    --border-hover: rgba(34, 211, 238, 0.3);
    --shadow-card: 0 4px 24px rgba(0, 0, 0, 0.25);
    --shadow-card-hover: 0 8px 40px rgba(0, 0, 0, 0.4);
    --tag-bg: rgba(34, 211, 238, 0.1);
    --tag-text: #22d3ee;
    --hero-bg: linear-gradient(135deg, #0f1117 0%, #1a1040 50%, #0f1117 100%);

    /* Typography */
    --font-body: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    --font-mono: 'JetBrains Mono', 'Fira Code', 'Cascadia Code', monospace;
    --fs-xs: 0.75rem;
    --fs-sm: 0.875rem;
    --fs-base: 1rem;
    --fs-lg: 1.125rem;
    --fs-xl: 1.25rem;
    --fs-2xl: 1.5rem;
    --fs-3xl: 1.875rem;
    --fs-4xl: 2.25rem;
    --fs-hero: clamp(2rem, 5vw, 3.5rem);

    /* Spacing */
    --space-xs: 0.25rem;
    --space-sm: 0.5rem;
    --space-md: 1rem;
    --space-lg: 1.5rem;
    --space-xl: 2rem;
    --space-2xl: 3rem;
    --space-3xl: 4rem;

    /* Layout */
    --max-width: 1200px;
    --content-width: 800px;
    --radius-sm: 6px;
    --radius-md: 12px;
    --radius-lg: 16px;

    /* Transitions */
    --transition-fast: 150ms ease;
    --transition-base: 250ms ease;
    --transition-slow: 400ms ease;
}

/* Light mode */
[data-theme="light"] {
    --bg-primary: #f8f9fc;
    --bg-secondary: #ffffff;
    --bg-card: #ffffff;
    --bg-card-hover: #f0f2f8;
    --bg-code: #f4f5f9;
    --bg-nav: rgba(248, 249, 252, 0.9);
    --text-primary: #1a1d2e;
    --text-secondary: #4a5068;
    --text-muted: #8890a8;
    --accent: #0891b2;
    --accent-secondary: #06b6d4;
    --accent-gradient: linear-gradient(135deg, #0891b2, #0284c7);
    --border-color: rgba(0, 0, 0, 0.08);
    --border-hover: rgba(8, 145, 178, 0.3);
    --shadow-card: 0 4px 24px rgba(0, 0, 0, 0.06);
    --shadow-card-hover: 0 8px 40px rgba(0, 0, 0, 0.1);
    --tag-bg: rgba(8, 145, 178, 0.08);
    --tag-text: #0891b2;
    --hero-bg: linear-gradient(135deg, #f8f9fc 0%, #e0e7ff 50%, #f8f9fc 100%);
}

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

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

body {
    font-family: var(--font-body);
    font-size: var(--fs-base);
    line-height: 1.7;
    color: var(--text-primary);
    background-color: var(--bg-primary);
    transition: background-color var(--transition-base), color var(--transition-base);
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

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

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

img {
    max-width: 100%;
    height: auto;
    border-radius: var(--radius-md);
}

/* --- Navigation --- */
.site-nav {
    position: sticky;
    top: 0;
    z-index: 100;
    background: var(--bg-nav);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    border-bottom: 1px solid var(--border-color);
    padding: var(--space-md) 0;
}

.nav-container {
    max-width: var(--max-width);
    margin: 0 auto;
    padding: 0 var(--space-xl);
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.nav-brand {
    display: flex;
    align-items: center;
    gap: var(--space-sm);
    font-size: var(--fs-xl);
    font-weight: 800;
    color: var(--text-primary);
    letter-spacing: -0.02em;
}

.nav-brand:hover {
    color: var(--accent);
}

.nav-brand .brand-icon {
    font-size: var(--fs-2xl);
}

.nav-links {
    display: flex;
    align-items: center;
    gap: var(--space-lg);
    list-style: none;
}

.nav-links a {
    color: var(--text-secondary);
    font-size: var(--fs-sm);
    font-weight: 500;
    letter-spacing: 0.02em;
    text-transform: uppercase;
    padding: var(--space-xs) 0;
    position: relative;
    transition: color var(--transition-fast);
}

.nav-links a::after {
    content: '';
    position: absolute;
    bottom: -2px;
    left: 0;
    width: 0;
    height: 2px;
    background: var(--accent-gradient);
    border-radius: 1px;
    transition: width var(--transition-base);
}

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

.nav-links a:hover::after {
    width: 100%;
}

/* Theme Toggle */
.theme-toggle {
    background: none;
    border: 1px solid var(--border-color);
    color: var(--text-secondary);
    cursor: pointer;
    padding: var(--space-sm);
    border-radius: var(--radius-sm);
    font-size: var(--fs-lg);
    line-height: 1;
    transition: all var(--transition-fast);
    display: flex;
    align-items: center;
    justify-content: center;
}

.theme-toggle:hover {
    background: var(--bg-card);
    color: var(--accent);
    border-color: var(--border-hover);
}

/* Mobile menu */
.nav-toggle {
    display: none;
    background: none;
    border: none;
    color: var(--text-primary);
    font-size: var(--fs-xl);
    cursor: pointer;
    padding: var(--space-sm);
}

/* --- Hero Section --- */
.hero {
    background: var(--hero-bg);
    padding: var(--space-3xl) var(--space-xl);
    text-align: center;
    position: relative;
    overflow: hidden;
}

.hero::before {
    content: '';
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    width: 600px;
    height: 600px;
    background: radial-gradient(circle, rgba(34, 211, 238, 0.08) 0%, transparent 70%);
    pointer-events: none;
}

.hero-content {
    max-width: var(--content-width);
    margin: 0 auto;
    position: relative;
    z-index: 1;
}

.hero-badge {
    display: inline-flex;
    align-items: center;
    gap: var(--space-sm);
    background: var(--tag-bg);
    color: var(--tag-text);
    padding: var(--space-xs) var(--space-md);
    border-radius: 50px;
    font-size: var(--fs-xs);
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.08em;
    margin-bottom: var(--space-lg);
    border: 1px solid rgba(34, 211, 238, 0.15);
}

.hero h1 {
    font-size: var(--fs-hero);
    font-weight: 800;
    line-height: 1.15;
    letter-spacing: -0.03em;
    margin-bottom: var(--space-lg);
}

.hero h1 .gradient-text {
    background: var(--accent-gradient);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.hero p {
    font-size: var(--fs-lg);
    color: var(--text-secondary);
    max-width: 600px;
    margin: 0 auto;
    line-height: 1.8;
}

/* --- Main Content --- */
.site-main {
    max-width: var(--max-width);
    margin: 0 auto;
    padding: var(--space-2xl) var(--space-xl);
    width: 100%;
    flex: 1;
}

.section-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin-bottom: var(--space-xl);
}

.section-header h2 {
    font-size: var(--fs-2xl);
    font-weight: 700;
    letter-spacing: -0.02em;
}

.section-header .view-all {
    font-size: var(--fs-sm);
    font-weight: 500;
    color: var(--accent);
}

/* --- Post Grid --- */
.post-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(340px, 1fr));
    gap: var(--space-xl);
}

/* --- Post Card --- */
.post-card {
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    overflow: hidden;
    transition: all var(--transition-base);
    display: flex;
    flex-direction: column;
}

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

.post-card-thumbnail {
    width: 100%;
    height: 200px;
    object-fit: cover;
    background: linear-gradient(135deg, var(--bg-secondary), var(--bg-card));
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 3rem;
    color: var(--text-muted);
    position: relative;
    overflow: hidden;
}

.post-card-thumbnail::after {
    content: '';
    position: absolute;
    inset: 0;
    background: linear-gradient(135deg, rgba(34, 211, 238, 0.05) 0%, rgba(14, 165, 233, 0.05) 100%);
}

.post-card-body {
    padding: var(--space-lg);
    display: flex;
    flex-direction: column;
    flex: 1;
}

.post-card-tags {
    display: flex;
    flex-wrap: wrap;
    gap: var(--space-sm);
    margin-bottom: var(--space-md);
}

.tag {
    background: var(--tag-bg);
    color: var(--tag-text);
    padding: 2px var(--space-sm);
    border-radius: var(--radius-sm);
    font-size: var(--fs-xs);
    font-weight: 600;
    letter-spacing: 0.02em;
}

.post-card-title {
    font-size: var(--fs-xl);
    font-weight: 700;
    line-height: 1.35;
    letter-spacing: -0.01em;
    margin-bottom: var(--space-sm);
}

.post-card-title a {
    color: var(--text-primary);
    transition: color var(--transition-fast);
}

.post-card-title a:hover {
    color: var(--accent);
}

.post-card-excerpt {
    font-size: var(--fs-sm);
    color: var(--text-secondary);
    line-height: 1.7;
    margin-bottom: var(--space-md);
    flex: 1;
}

.post-card-meta {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding-top: var(--space-md);
    border-top: 1px solid var(--border-color);
    font-size: var(--fs-xs);
    color: var(--text-muted);
}

.post-card-meta .read-time {
    display: flex;
    align-items: center;
    gap: 4px;
}

/* --- Featured Post --- */
.featured-post {
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: var(--space-2xl);
    margin-bottom: var(--space-2xl);
    position: relative;
    overflow: hidden;
    transition: all var(--transition-base);
}

.featured-post:hover {
    border-color: var(--border-hover);
    box-shadow: var(--shadow-card-hover);
}

.featured-post::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 3px;
    background: var(--accent-gradient);
}

.featured-label {
    display: inline-flex;
    align-items: center;
    gap: var(--space-xs);
    background: var(--accent-gradient);
    color: #fff;
    padding: 3px var(--space-md);
    border-radius: 50px;
    font-size: var(--fs-xs);
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.08em;
    margin-bottom: var(--space-lg);
}

.featured-post h2 {
    font-size: var(--fs-3xl);
    font-weight: 800;
    line-height: 1.25;
    letter-spacing: -0.02em;
    margin-bottom: var(--space-md);
}

.featured-post h2 a {
    color: var(--text-primary);
}

.featured-post h2 a:hover {
    color: var(--accent);
}

.featured-post .excerpt {
    font-size: var(--fs-lg);
    color: var(--text-secondary);
    line-height: 1.8;
    margin-bottom: var(--space-lg);
}

.featured-meta {
    display: flex;
    align-items: center;
    gap: var(--space-lg);
    font-size: var(--fs-sm);
    color: var(--text-muted);
}

/* --- Article (Post) Layout --- */
.article-container {
    max-width: var(--content-width);
    margin: 0 auto;
    padding: var(--space-2xl) var(--space-xl);
}

.article-header {
    margin-bottom: var(--space-2xl);
    padding-bottom: var(--space-xl);
    border-bottom: 1px solid var(--border-color);
}

.article-header .post-tags {
    display: flex;
    flex-wrap: wrap;
    gap: var(--space-sm);
    margin-bottom: var(--space-lg);
}

.article-header h1 {
    font-size: var(--fs-4xl);
    font-weight: 800;
    line-height: 1.2;
    letter-spacing: -0.03em;
    margin-bottom: var(--space-lg);
}

.article-meta {
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    gap: var(--space-lg);
    color: var(--text-muted);
    font-size: var(--fs-sm);
}

.article-meta .meta-item {
    display: flex;
    align-items: center;
    gap: 6px;
}

/* --- Article Content --- */
.article-content {
    font-size: var(--fs-lg);
    line-height: 1.85;
    color: var(--text-secondary);
}

.article-content h2 {
    font-size: var(--fs-2xl);
    font-weight: 700;
    color: var(--text-primary);
    margin-top: var(--space-2xl);
    margin-bottom: var(--space-md);
    letter-spacing: -0.02em;
}

.article-content h3 {
    font-size: var(--fs-xl);
    font-weight: 600;
    color: var(--text-primary);
    margin-top: var(--space-xl);
    margin-bottom: var(--space-md);
}

.article-content p {
    margin-bottom: var(--space-lg);
}

.article-content ul,
.article-content ol {
    margin-bottom: var(--space-lg);
    padding-left: var(--space-xl);
}

.article-content li {
    margin-bottom: var(--space-sm);
}

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

.article-content a {
    color: var(--accent);
    text-decoration: underline;
    text-decoration-color: rgba(34, 211, 238, 0.3);
    text-underline-offset: 3px;
    transition: text-decoration-color var(--transition-fast);
}

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

.article-content blockquote {
    border-left: 3px solid var(--accent);
    padding: var(--space-md) var(--space-lg);
    margin: var(--space-xl) 0;
    background: var(--bg-card);
    border-radius: 0 var(--radius-md) var(--radius-md) 0;
    color: var(--text-secondary);
    font-style: italic;
}

/* Code Blocks */
.article-content code {
    font-family: var(--font-mono);
    font-size: 0.9em;
    background: var(--bg-code);
    padding: 2px 6px;
    border-radius: 4px;
    color: var(--accent);
}

.article-content pre {
    background: var(--bg-code);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: var(--space-lg);
    overflow-x: auto;
    margin: var(--space-xl) 0;
    position: relative;
}

.article-content pre code {
    background: none;
    padding: 0;
    color: var(--text-primary);
    font-size: var(--fs-sm);
    line-height: 1.7;
}

.article-content table {
    width: 100%;
    border-collapse: collapse;
    margin: var(--space-xl) 0;
    font-size: var(--fs-sm);
}

.article-content th,
.article-content td {
    text-align: left;
    padding: var(--space-sm) var(--space-md);
    border-bottom: 1px solid var(--border-color);
}

.article-content th {
    color: var(--text-primary);
    font-weight: 600;
    background: var(--bg-card);
}

.article-content img {
    margin: var(--space-xl) 0;
    border: 1px solid var(--border-color);
}

/* --- Article Footer --- */
.article-footer {
    margin-top: var(--space-2xl);
    padding-top: var(--space-xl);
    border-top: 1px solid var(--border-color);
}

.back-link {
    display: inline-flex;
    align-items: center;
    gap: var(--space-sm);
    color: var(--accent);
    font-weight: 500;
    font-size: var(--fs-sm);
    padding: var(--space-sm) var(--space-md);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-sm);
    transition: all var(--transition-fast);
}

.back-link:hover {
    background: var(--tag-bg);
    border-color: var(--border-hover);
}

/* --- Related Posts --- */
.related-posts {
    margin-top: var(--space-2xl);
}

.related-posts h3 {
    font-size: var(--fs-xl);
    font-weight: 700;
    margin-bottom: var(--space-lg);
}

.related-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(250px, 1fr));
    gap: var(--space-md);
}

.related-card {
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: var(--space-lg);
    transition: all var(--transition-fast);
}

.related-card:hover {
    border-color: var(--border-hover);
    transform: translateY(-2px);
}

.related-card h4 {
    font-size: var(--fs-base);
    font-weight: 600;
    margin-bottom: var(--space-xs);
}

.related-card h4 a {
    color: var(--text-primary);
}

.related-card h4 a:hover {
    color: var(--accent);
}

.related-card .date {
    font-size: var(--fs-xs);
    color: var(--text-muted);
}

/* --- Footer --- */
.site-footer {
    background: var(--bg-secondary);
    border-top: 1px solid var(--border-color);
    padding: var(--space-2xl) var(--space-xl);
    margin-top: auto;
}

.footer-container {
    max-width: var(--max-width);
    margin: 0 auto;
    display: grid;
    grid-template-columns: 2fr 1fr 1fr;
    gap: var(--space-2xl);
}

.footer-brand h3 {
    font-size: var(--fs-xl);
    font-weight: 700;
    margin-bottom: var(--space-md);
}

.footer-brand p {
    color: var(--text-secondary);
    font-size: var(--fs-sm);
    line-height: 1.7;
    max-width: 350px;
}

.footer-section h4 {
    font-size: var(--fs-sm);
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.08em;
    color: var(--text-muted);
    margin-bottom: var(--space-md);
}

.footer-section ul {
    list-style: none;
}

.footer-section li {
    margin-bottom: var(--space-sm);
}

.footer-section a {
    color: var(--text-secondary);
    font-size: var(--fs-sm);
    transition: color var(--transition-fast);
}

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

.footer-bottom {
    max-width: var(--max-width);
    margin: var(--space-xl) auto 0;
    padding-top: var(--space-lg);
    border-top: 1px solid var(--border-color);
    text-align: center;
    color: var(--text-muted);
    font-size: var(--fs-xs);
}

/* --- Empty State --- */
.empty-state {
    text-align: center;
    padding: var(--space-3xl) var(--space-xl);
}

.empty-state .emoji {
    font-size: 3rem;
    margin-bottom: var(--space-md);
}

.empty-state h3 {
    font-size: var(--fs-xl);
    margin-bottom: var(--space-sm);
}

.empty-state p {
    color: var(--text-secondary);
}

/* --- Responsive --- */
@media (max-width: 768px) {
    .nav-links {
        display: none;
        position: absolute;
        top: 100%;
        left: 0;
        right: 0;
        background: var(--bg-nav);
        backdrop-filter: blur(20px);
        -webkit-backdrop-filter: blur(20px);
        border-bottom: 1px solid var(--border-color);
        flex-direction: column;
        padding: var(--space-md) var(--space-xl);
        gap: var(--space-sm);
    }

    .nav-links.open {
        display: flex;
    }

    .nav-toggle {
        display: block;
    }

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

    .footer-container {
        grid-template-columns: 1fr;
        gap: var(--space-xl);
    }

    .hero {
        padding: var(--space-2xl) var(--space-lg);
    }

    .featured-post {
        padding: var(--space-lg);
    }

    .article-header h1 {
        font-size: var(--fs-2xl);
    }

    .article-container {
        padding: var(--space-lg);
    }
}

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

    .post-card-thumbnail {
        height: 160px;
    }

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

/* --- Selection --- */
::selection {
    background: rgba(34, 211, 238, 0.25);
    color: var(--text-primary);
}

/* --- Scrollbar --- */
::-webkit-scrollbar {
    width: 8px;
    height: 8px;
}

::-webkit-scrollbar-track {
    background: var(--bg-primary);
}

::-webkit-scrollbar-thumb {
    background: var(--text-muted);
    border-radius: 4px;
}

::-webkit-scrollbar-thumb:hover {
    background: var(--text-secondary);
}

/* --- Animations --- */
@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(20px);
    }

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

.post-card {
    animation: fadeInUp 0.5s ease both;
}

.post-card:nth-child(2) {
    animation-delay: 0.1s;
}

.post-card:nth-child(3) {
    animation-delay: 0.2s;
}

.post-card:nth-child(4) {
    animation-delay: 0.3s;
}

.post-card:nth-child(5) {
    animation-delay: 0.4s;
}

.post-card:nth-child(6) {
    animation-delay: 0.5s;
}