/* ========================================
   CSS Variables - Colors, Fonts, Spacing
   ======================================== */

/* Color Palette - Light Mode */
:root {
    /* Primary Colors */
    --accent: #3182ce;
    --accent-hover: #2b6cb0;
    --accent-light: #63b3ed;
    
    /* Background & Surface */
    --bg: #f7fafc;
    --card-bg: #ffffff;
    
    /* Text Colors */
    --fg: #2d3748;
    --muted: #718096;
    --muted-light: #a0aec0;
    
    /* Borders */
    --border: #e2e8f0;
    --border-light: #edf2f7;
    --card-border: rgba(0, 0, 0, 0.08);
    
    /* Shadows */
    --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -2px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -4px rgba(0, 0, 0, 0.1);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 8px 10px -6px rgba(0, 0, 0, 0.1);
    --shadow-accent: 0 4px 14px 0 rgba(59, 130, 246, 0.25);
    
    /* Typography */
    --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    --font-mono: 'SF Mono', Monaco, 'Courier New', monospace;
    
    /* Spacing */
    --space-xs: 0.25rem;
    --space-sm: 0.5rem;
    --space-md: 1rem;
    --space-lg: 1.5rem;
    --space-xl: 2rem;
    --space-2xl: 3rem;
    
    /* Border Radius */
    --radius-sm: 0.375rem;
    --radius-md: 0.5rem;
    --radius-lg: 0.75rem;
    --radius-xl: 1rem;
    --radius-2xl: 1.5rem;
    --radius-full: 9999px;
}

/* Color Palette - Dark Mode */
[data-theme="dark"] {
    --accent: #63b3ed;
    --accent-hover: #90cdf4;
    --accent-light: #3182ce;
    
    --bg: #1a202c;
    --card-bg: #2d3748;
    
    --fg: #e2e8f0;
    --muted: #a0aec0;
    --muted-light: #718096;
    
    --border: #2d3748;
    --border-light: #1a202c;
    --card-border: rgba(255, 255, 255, 0.08);
    
    --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.3);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.4), 0 2px 4px -2px rgba(0, 0, 0, 0.3);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.5), 0 4px 6px -4px rgba(0, 0, 0, 0.4);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.6), 0 8px 10px -6px rgba(0, 0, 0, 0.5);
    --shadow-accent: 0 4px 14px 0 rgba(99, 179, 237, 0.3);
}

/* Auto Dark Mode */
@media (prefers-color-scheme: dark) {
    :root:not([data-theme="light"]) {
        --accent: #63b3ed;
        --accent-hover: #90cdf4;
        --accent-light: #3182ce;
        
        --bg: #1a202c;
        --card-bg: #2d3748;
        
        --fg: #e2e8f0;
        --muted: #a0aec0;
        --muted-light: #718096;
        
        --border: #2d3748;
        --border-light: #1a202c;
        --card-border: rgba(255, 255, 255, 0.08);
    }
}
/* ========================================
   Base - Reset & Typography
   ======================================== */

@import url('https://fonts.googleapis.com/css2?family=Inter:wght@400;450;500;600;700;800;900&display=swap');

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

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

body {
    font-family: var(--font-sans);
    background-color: var(--bg);
    color: var(--fg);
    line-height: 1.65;
    transition: background-color 0.3s ease, color 0.3s ease;
}

/* Typography */
h1, h2, h3, h4, h5, h6 {
    font-weight: 700;
    line-height: 1.2;
    letter-spacing: -0.02em;
    color: var(--fg);
}

h1 { font-size: 2.5rem; font-weight: 800; letter-spacing: -0.04em; }
h2 { font-size: 1.75rem; font-weight: 700; letter-spacing: -0.03em; }
h3 { font-size: 1.25rem; font-weight: 600; }

p {
    margin-bottom: 1.25rem;
    color: var(--fg);
}

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

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

/* Container */
.container {
    max-width: 1100px;
    margin: 0 auto;
    padding: 0 var(--space-lg);
}

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

/* Focus */
a:focus-visible,
button:focus-visible,
input:focus-visible {
    outline: 2px solid var(--accent);
    outline-offset: 2px;
}

/* Animations */
@keyframes fadeIn {
    from { opacity: 0; transform: translateY(10px); }
    to { opacity: 1; transform: translateY(0); }
}
/* ========================================
   Components - Cards, Buttons, Tags
   ======================================== */

/* Article Cards */
.articles-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
    gap: var(--space-lg);
    margin-top: var(--space-xl);
}

.article-card {
    background: var(--card-bg);
    border: 1px solid var(--card-border);
    border-radius: var(--radius-xl);
    padding: var(--space-lg);
    transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    display: flex;
    flex-direction: column;
    gap: var(--space-md);
    position: relative;
    overflow: hidden;
    animation: fadeIn 0.4s ease-out;
    animation-fill-mode: both;
}

.article-card:nth-child(1) { animation-delay: 0.05s; }
.article-card:nth-child(2) { animation-delay: 0.1s; }
.article-card:nth-child(3) { animation-delay: 0.15s; }
.article-card:nth-child(4) { animation-delay: 0.2s; }
.article-card:nth-child(5) { animation-delay: 0.25s; }
.article-card:nth-child(6) { animation-delay: 0.3s; }

.article-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 3px;
    background: linear-gradient(90deg, var(--accent), var(--accent-light));
    opacity: 0;
    transition: opacity 0.3s ease;
}

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

.article-card:hover::before {
    opacity: 1;
}

/* Card Content */
.article-meta {
    font-size: 0.75rem;
    font-weight: 600;
    color: var(--accent);
    text-transform: uppercase;
    letter-spacing: 0.05em;
    display: flex;
    align-items: center;
    gap: var(--space-sm);
}

.article-card h3 {
    font-size: 1.25rem;
    font-weight: 700;
    line-height: 1.3;
}

.article-card h3 a {
    color: var(--fg);
    text-decoration: none;
    transition: color 0.2s ease;
}

.article-card h3 a:hover {
    color: var(--accent);
}

.article-card p {
    color: var(--muted);
    font-size: 0.95rem;
    line-height: 1.6;
    display: -webkit-box;
    -webkit-line-clamp: 3;
    -webkit-box-orient: vertical;
    overflow: hidden;
}

.read-link {
    display: inline-flex;
    align-items: center;
    gap: var(--space-sm);
    font-weight: 600;
    color: var(--accent);
    text-decoration: none;
    font-size: 0.9rem;
    margin-top: auto;
    transition: gap 0.2s ease;
}

.read-link:hover {
    gap: 0.75rem;
}

/* Article Tags */
.article-tags {
    display: flex;
    flex-wrap: wrap;
    gap: 0.4rem;
    margin-top: 0.25rem;
}

.article-tags .tag {
    display: inline-block;
    padding: 0.25rem 0.6rem;
    font-size: 0.7rem;
    font-weight: 600;
    color: var(--muted);
    background: var(--bg);
    border: 1px solid var(--border);
    border-radius: var(--radius-full);
    text-transform: uppercase;
    letter-spacing: 0.03em;
}

.article-tags .tag.category-tag {
    color: var(--accent);
    border-color: var(--accent);
    background: rgba(59, 130, 246, 0.1);
}

.article-tags .tag:hover {
    border-color: var(--accent);
    color: var(--accent);
}

/* Article Footer */
.article-footer {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    margin-top: auto;
    padding-top: var(--space-sm);
    border-top: 1px solid var(--border-light);
}

.article-footer .source,
.article-footer .model {
    font-size: 0.7rem;
    font-weight: 600;
    color: var(--muted-light);
    text-transform: uppercase;
    letter-spacing: 0.04em;
}

/* Buttons */
.tag-btn {
    background: var(--card-bg);
    border: 1px solid var(--border);
    padding: var(--space-sm) var(--space-md);
    border-radius: var(--radius-lg);
    font-size: 0.8rem;
    font-weight: 600;
    color: var(--muted);
    cursor: pointer;
    transition: all 0.2s ease;
    text-transform: uppercase;
    letter-spacing: 0.03em;
}

.tag-btn:hover {
    border-color: var(--accent);
    color: var(--accent);
    transform: translateY(-1px);
}

.tag-btn.active {
    background: var(--accent);
    color: white;
    border-color: var(--accent);
    box-shadow: var(--shadow-accent);
}

/* Search */
.search-container {
    position: relative;
    max-width: 300px;
}

.search-icon {
    position: absolute;
    left: 0.75rem;
    top: 50%;
    transform: translateY(-50%);
    color: var(--muted-light);
    pointer-events: none;
}

#article-search {
    width: 100%;
    padding: 0.6rem 1rem 0.6rem 2.5rem;
    background: var(--card-bg);
    border: 1px solid var(--border);
    border-radius: var(--radius-lg);
    font-size: 0.9rem;
    color: var(--fg);
    font-family: inherit;
    transition: all 0.2s ease;
}

#article-search::placeholder {
    color: var(--muted-light);
}

#article-search:focus {
    outline: none;
    border-color: var(--accent);
    box-shadow: 0 0 0 3px rgba(59, 130, 246, 0.15);
}

/* Theme Toggle */
#theme-toggle {
    background: var(--card-bg);
    border: 1px solid var(--border);
    padding: var(--space-sm);
    cursor: pointer;
    color: var(--muted);
    border-radius: var(--radius-md);
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all 0.2s ease;
}

#theme-toggle:hover {
    background: var(--accent);
    color: white;
    border-color: var(--accent);
    transform: scale(1.05);
}

#theme-toggle svg {
    width: 18px;
    height: 18px;
}

/* Load More */
#load-more-btn {
    background: var(--card-bg);
    border: 1px solid var(--border);
    padding: 0.75rem 1.5rem;
    border-radius: var(--radius-lg);
    font-size: 0.9rem;
    font-weight: 600;
    color: var(--fg);
    cursor: pointer;
    transition: all 0.2s ease;
    display: inline-flex;
    align-items: center;
    gap: var(--space-sm);
    margin-top: var(--space-xl);
}

#load-more-btn:hover {
    background: var(--accent);
    color: white;
    border-color: var(--accent);
    transform: translateY(-2px);
    box-shadow: var(--shadow-accent);
}

/* Post Tags */
.post-tags {
    display: flex;
    flex-wrap: wrap;
    gap: var(--space-sm);
    padding: var(--space-lg) 2.5rem;
    background: var(--bg);
    border-top: 1px solid var(--border);
}

.post-tags .tag-btn {
    background: var(--card-bg);
    border: 1px solid var(--border);
    padding: 0.4rem 0.85rem;
    border-radius: var(--radius-full);
    font-size: 0.75rem;
    font-weight: 600;
    color: var(--muted);
    text-transform: uppercase;
    letter-spacing: 0.03em;
}

.post-tags .tag-btn:hover {
    border-color: var(--accent);
    color: var(--accent);
}
/* ========================================
   Layout - Header, Hero, Footer
   ======================================== */

/* Header */
body > header {
    position: sticky;
    top: 0;
    z-index: 100;
    background: rgba(250, 251, 252, 0.85);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border-bottom: 1px solid var(--border-light);
    padding: var(--space-md) 0;
    transition: all 0.3s ease;
}

[data-theme="dark"] body > header {
    background: rgba(26, 32, 44, 0.85);
}

nav {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: var(--space-md);
}

.logo {
    font-size: 1.5rem;
    font-weight: 800;
    color: var(--fg);
    text-decoration: none;
    letter-spacing: -0.03em;
    white-space: nowrap;
}

.logo-accent {
    background: linear-gradient(135deg, var(--accent), var(--accent-hover));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.header-actions {
    display: flex;
    align-items: center;
    gap: var(--space-lg);
}

.header-actions a {
    color: var(--muted);
    font-size: 0.9rem;
    font-weight: 500;
    text-decoration: none;
    transition: color 0.2s ease;
    position: relative;
}

.header-actions a:hover,
.header-actions a.active {
    color: var(--fg);
}

.header-actions a.active::after {
    content: '';
    position: absolute;
    bottom: -4px;
    left: 0;
    width: 100%;
    height: 2px;
    background: var(--accent);
    border-radius: 1px;
}

/* Hero */
.hero {
    padding: var(--space-2xl) 0 3rem;
    max-width: 800px;
}

.hero h1 {
    font-size: clamp(2rem, 5vw, 3.5rem);
    font-weight: 800;
    line-height: 1.1;
    letter-spacing: -0.04em;
    margin-bottom: var(--space-md);
    color: var(--fg);
}

.hero-subtitle {
    font-size: clamp(1rem, 2vw, 1.25rem);
    color: var(--muted);
    line-height: 1.6;
    max-width: 600px;
}

/* Controls */
.controls-container {
    margin-bottom: var(--space-xl);
    padding-bottom: var(--space-lg);
    border-bottom: 1px solid var(--border-light);
}

.tag-filter-scroll {
    display: flex;
    flex-wrap: wrap;
    gap: var(--space-sm);
}

/* Section Titles */
.section-title {
    font-size: 0.75rem;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.1em;
    color: var(--accent);
    margin-bottom: var(--space-xl);
    display: flex;
    align-items: center;
    gap: var(--space-md);
}

.section-title::after {
    content: '';
    height: 1px;
    flex: 1;
    background: linear-gradient(90deg, var(--border), transparent);
}

/* Post Layout */
.post-layout-container {
    max-width: 800px;
    margin: 0 auto;
    padding: 3rem var(--space-lg);
}

.post-advanced {
    background: var(--card-bg);
    border: 1px solid var(--border);
    border-radius: var(--radius-2xl);
    overflow: hidden;
    box-shadow: var(--shadow-lg);
}

.post-header-advanced {
    background: linear-gradient(90deg, #E8F4F8 0%, #C7E5E8 50%, #AED9E0 100%);
    padding: 2.5rem;
    color: #1e293b;
}

[data-theme="dark"] .post-header-advanced {
    background: linear-gradient(135deg, #4e5875 0%, #091433 100%);
}

.post-meta-advanced {
    display: flex;
    flex-wrap: wrap;
    gap: var(--space-sm);
    margin-top: var(--space-md);
}

.post-tag-item {
    display: inline-flex;
    align-items: center;
    background: var(--card-bg);
    border: 1px solid var(--border);
    border-radius: 9999px;
    padding: 0.35rem 0.85rem;
    font-size: 0.75rem;
    font-weight: 500;
    color: var(--fg);
    text-transform: uppercase;
    letter-spacing: 0.02em;
    transition: all 0.2s ease;
}

.post-tag-item:hover {
    border-color: var(--accent);
    color: var(--accent);
    transform: translateY(-1px);
}

.post-tag-item a {
    color: var(--fg);
    text-decoration: none;
}

.post-tag-item a:hover {
    color: var(--accent);
}

[data-theme="dark"] .post-tag-item {
    background: var(--card-bg);
    border-color: var(--border);
}

[data-theme="dark"] .post-tag-item:hover {
    border-color: var(--accent);
}

/* Post Content */
.post-description {
    padding: var(--space-lg) 2.5rem;
    background: var(--bg);
    border-bottom: 1px solid var(--border);
    font-size: 1.15rem;
    color: var(--muted);
    font-style: italic;
    line-height: 1.7;
}

.post-description p {
    margin-bottom: 0;
}

.post-body-advanced {
    padding: 2.5rem;
    font-size: 1.125rem;
    line-height: 1.8;
    color: var(--fg);
}

.post-body-advanced h1 { font-size: 2rem; font-weight: 800; margin-bottom: var(--space-lg); }
.post-body-advanced h2 { font-size: 1.5rem; font-weight: 700; margin: 2.5rem 0 var(--space-sm); }
.post-body-advanced h3 { font-size: 1.25rem; font-weight: 600; margin: var(--space-xl) 0 var(--space-sm); }
.post-body-advanced p { margin-bottom: var(--space-lg); }
.post-body-advanced ul, .post-body-advanced ol { margin-bottom: var(--space-lg); padding-left: var(--space-lg); }
.post-body-advanced li { margin-bottom: var(--space-sm); }

.post-body-advanced strong { font-weight: 700; }
.post-body-advanced em { font-style: italic; color: var(--muted); }

.post-body-advanced blockquote {
    border-left: 4px solid var(--accent);
    padding: var(--space-md) var(--space-lg);
    margin: var(--space-xl) 0;
    background: rgba(59, 130, 246, 0.05);
    border-radius: 0 var(--radius-md) var(--radius-md) 0;
    font-style: italic;
    color: var(--muted);
}

.post-body-advanced code {
    background: rgba(59, 130, 246, 0.1);
    padding: 0.2rem 0.5rem;
    border-radius: var(--radius-sm);
    font-size: 0.9em;
    font-family: var(--font-mono);
    color: var(--accent);
}

.post-body-advanced pre {
    background: var(--bg);
    border: 1px solid var(--border);
    border-radius: var(--radius-lg);
    padding: var(--space-lg);
    overflow-x: auto;
    margin: var(--space-lg) 0;
}

.post-body-advanced pre code {
    background: transparent;
    padding: 0;
    color: var(--fg);
}

.post-body-advanced img {
    width: 100%;
    height: auto;
    border-radius: var(--radius-lg);
    margin: var(--space-xl) 0;
    box-shadow: var(--shadow-md);
}

.post-body-advanced a {
    color: var(--accent);
    text-decoration: underline;
    text-underline-offset: 2px;
}

.post-body-advanced a:hover {
    color: var(--accent-hover);
}

/* Post Footer */
.post-footer-advanced {
    padding: var(--space-lg) 2.5rem;
    background: var(--bg);
    border-top: 1px solid var(--border);
}

.back-link-advanced {
    display: inline-flex;
    align-items: center;
    gap: var(--space-sm);
    color: var(--muted);
    font-weight: 600;
    font-size: 0.9rem;
    transition: all 0.2s ease;
}

.back-link-advanced:hover {
    color: var(--accent);
    gap: 0.75rem;
}

/* About */
.about-hero {
    padding: 4rem 0;
}

.about-hero h1 {
    font-size: clamp(2.5rem, 8vw, 4rem);
    font-weight: 800;
    line-height: 1.1;
    margin-bottom: var(--space-lg);
}

.about-content {
    max-width: 700px;
    font-size: 1.15rem;
    line-height: 1.75;
}

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

/* Footer */
footer {
    padding: 3rem 0;
    border-top: 1px solid var(--border-light);
    margin-top: 4rem;
}

.footer-content {
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
    gap: var(--space-md);
    font-size: 0.9rem;
    color: var(--muted);
}

.footer-links {
    display: flex;
    gap: var(--space-lg);
}

.footer-links a {
    color: var(--muted);
    transition: color 0.2s ease;
}

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

.footer-links svg {
    width: 20px;
    height: 20px;
}

/* Reading Progress */
.progress-container {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 3px;
    background: transparent;
    z-index: 1000;
}

.progress-bar {
    height: 100%;
    background: linear-gradient(90deg, var(--accent), var(--accent-light));
    width: 0%;
    transition: width 0.1s ease-out;
}

/* Related Posts */
.related-posts {
    margin-top: 3rem;
    padding-top: var(--space-xl);
    border-top: 1px solid var(--border);
}

.related-posts h3 {
    font-size: 1.25rem;
    margin-bottom: var(--space-lg);
}

.related-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: var(--space-md);
}

.related-card {
    background: var(--card-bg);
    border: 1px solid var(--border);
    border-radius: var(--radius-lg);
    padding: var(--space-lg);
    transition: all 0.2s ease;
}

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

.related-card h4 {
    font-size: 1rem;
    font-weight: 600;
    line-height: 1.3;
    margin-bottom: var(--space-sm);
}

.related-card h4 a {
    color: var(--fg);
    text-decoration: none;
}

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

.related-card .date {
    font-size: 0.8rem;
    color: var(--muted);
}

/* Responsive */
@media (max-width: 768px) {
    .container { padding: 0 var(--space-md); }
    nav { flex-wrap: wrap; gap: var(--space-md); }
    .header-actions { gap: var(--space-md); }
    .hero { padding: 3rem 0 2rem; }
    .hero h1 { font-size: 1.75rem; }
    .articles-grid { grid-template-columns: 1fr; gap: var(--space-md); }
    .article-card { padding: var(--space-lg); }
    .post-layout-container { padding: var(--space-lg) var(--space-md); }
    .post-header-advanced { padding: var(--space-lg); }
    .post-body-advanced { padding: var(--space-lg); font-size: 1rem; }
    .footer-content { flex-direction: column; text-align: center; }
    .related-grid { grid-template-columns: 1fr; }
    .tag-filter-scroll { overflow-x: auto; flex-wrap: nowrap; }
}