/* ===== CSS Variables & Theme ===== */
:root {
    /* Light theme colors */
    --bg-primary: #ffffff;
    --bg-secondary: #f8f9fa;
    --bg-tertiary: #e9ecef;
    --text-primary: #212529;
    --text-secondary: #6c757d;
    --text-tertiary: #adb5bd;
    --accent: #6366f1;
    --accent-hover: #4f46e5;
    --border: #dee2e6;
    --shadow: rgba(0, 0, 0, 0.1);
    --code-bg: #f8f9fa;
    --code-border: #e9ecef;

    /* Spacing */
    --container-width: 900px;
    --container-narrow: 720px;
    --spacing-xs: 0.5rem;
    --spacing-sm: 1rem;
    --spacing-md: 1.5rem;
    --spacing-lg: 2rem;
    --spacing-xl: 3rem;

    /* Typography */
    --font-sans: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
    --font-mono: 'SF Mono', Monaco, 'Cascadia Code', 'Courier New', monospace;
    --line-height-base: 1.7;
    --line-height-heading: 1.3;
}

[data-theme="dark"] {
    --bg-primary: #1a1a1a;
    --bg-secondary: #242424;
    --bg-tertiary: #2d2d2d;
    --text-primary: #e4e4e7;
    --text-secondary: #a1a1aa;
    --text-tertiary: #71717a;
    --accent: #818cf8;
    --accent-hover: #a5b4fc;
    --border: #3f3f46;
    --shadow: rgba(0, 0, 0, 0.3);
    --code-bg: #242424;
    --code-border: #3f3f46;
}

/* ===== Base Styles ===== */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    font-size: 16px;
    scroll-behavior: smooth;
    scroll-padding-top: 80px; /* Account for sticky header */
}

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

/* ===== Typography ===== */
h1, h2, h3, h4, h5, h6 {
    line-height: var(--line-height-heading);
    font-weight: 700;
    margin-bottom: var(--spacing-md);
    color: var(--text-primary);
}

h1 { font-size: 2.5rem; }
h2 { font-size: 2rem; }
h3 { font-size: 1.75rem; }
h4 { font-size: 1.5rem; }
h5 { font-size: 1.25rem; }
h6 { font-size: 1rem; }

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

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

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

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

.container-narrow {
    max-width: var(--container-narrow);
    margin: 0 auto;
    padding: 0 var(--spacing-md);
}

/* ===== Header ===== */
.site-header {
    background-color: var(--bg-primary);
    border-bottom: 1px solid var(--border);
    padding: var(--spacing-md) 0;
    position: sticky;
    top: 0;
    z-index: 100;
    backdrop-filter: blur(10px);
    background-color: rgba(255, 255, 255, 0.9);
}

[data-theme="dark"] .site-header {
    background-color: rgba(26, 26, 26, 0.9);
}

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

.site-title {
    font-size: 1.5rem;
    margin: 0;
}

.site-title a {
    color: var(--text-primary);
    text-decoration: none;
    font-weight: 700;
}

.theme-toggle {
    background: none;
    border: 1px solid var(--border);
    border-radius: 8px;
    padding: var(--spacing-xs);
    cursor: pointer;
    color: var(--text-primary);
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all 0.2s ease;
    width: 40px;
    height: 40px;
}

.theme-toggle:hover {
    background-color: var(--bg-secondary);
}

.theme-toggle svg {
    width: 20px;
    height: 20px;
}

.sun-icon {
    display: none;
}

.moon-icon {
    display: block;
}

[data-theme="dark"] .sun-icon {
    display: block;
}

[data-theme="dark"] .moon-icon {
    display: none;
}

.nav {
    display: flex;
    gap: var(--spacing-md);
}

.nav-link {
    color: var(--text-secondary);
    padding: var(--spacing-xs) 0;
    position: relative;
    font-weight: 500;
}

.nav-link:hover,
.nav-link.active {
    color: var(--accent);
}

.nav-link.active::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 0;
    right: 0;
    height: 2px;
    background-color: var(--accent);
}

/* ===== Main Content ===== */
.main-content {
    min-height: calc(100vh - 200px);
    padding: var(--spacing-xl) 0;
}

/* ===== Hero Section ===== */
.hero {
    text-align: center;
    padding: var(--spacing-xl) 0;
    margin-bottom: var(--spacing-xl);
}

.hero h2 {
    font-size: 2.5rem;
    margin-bottom: var(--spacing-sm);
}

.hero p {
    font-size: 1.25rem;
    color: var(--text-secondary);
    margin-bottom: 0;
}

/* ===== Posts Grid ===== */
.posts-section {
    margin-top: var(--spacing-xl);
}

.section-title {
    margin-bottom: var(--spacing-lg);
    font-size: 1.75rem;
}

.posts-grid {
    display: grid;
    gap: var(--spacing-lg);
}

.post-card {
    background-color: var(--bg-secondary);
    border: 1px solid var(--border);
    border-radius: 12px;
    padding: var(--spacing-lg);
    transition: all 0.3s ease;
    cursor: pointer;
}

.post-card:hover {
    transform: translateY(-4px);
    box-shadow: 0 8px 24px var(--shadow);
    border-color: var(--accent);
}

.post-card-title {
    font-size: 1.5rem;
    margin-bottom: var(--spacing-sm);
}

.post-card-title a {
    color: var(--text-primary);
    text-decoration: none;
}

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

.post-card-meta {
    display: flex;
    gap: var(--spacing-md);
    color: var(--text-secondary);
    font-size: 0.875rem;
    margin-bottom: var(--spacing-sm);
}

.post-card-excerpt {
    color: var(--text-secondary);
    margin-bottom: var(--spacing-sm);
}

.post-card-tags {
    display: flex;
    flex-wrap: wrap;
    gap: var(--spacing-xs);
}

.tag {
    background-color: var(--bg-tertiary);
    color: var(--text-secondary);
    padding: 0.25rem 0.75rem;
    border-radius: 16px;
    font-size: 0.75rem;
    font-weight: 500;
}

/* ===== Post Page ===== */
.post-container {
    padding-top: var(--spacing-lg);
}

.post-header {
    margin-bottom: var(--spacing-xl);
    position: relative;
}

.back-link {
    display: inline-block;
    color: var(--text-secondary);
    margin-bottom: var(--spacing-md);
    font-size: 0.875rem;
}

.back-link:hover {
    color: var(--accent);
}

.post-title {
    font-size: 3rem;
    margin-bottom: var(--spacing-md);
    line-height: 1.2;
}

.post-meta {
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: var(--spacing-md);
    color: var(--text-secondary);
    font-size: 0.875rem;
    padding-bottom: var(--spacing-lg);
    border-bottom: 1px solid var(--border);
}

.post-meta-left {
    display: flex;
    gap: var(--spacing-md);
    align-items: center;
}

/* Copy as Markdown Button */
.copy-markdown-btn {
    display: inline-flex;
    align-items: center;
    gap: var(--spacing-xs);
    background-color: var(--bg-secondary);
    border: 1px solid var(--border);
    border-radius: 8px;
    padding: var(--spacing-xs) var(--spacing-md);
    cursor: pointer;
    color: var(--text-primary);
    font-family: var(--font-sans);
    font-size: 0.875rem;
    font-weight: 500;
    transition: all 0.2s ease;
    white-space: nowrap;
}

.copy-markdown-btn:hover {
    background-color: var(--bg-tertiary);
    border-color: var(--accent);
    color: var(--accent);
}

.copy-markdown-btn:active {
    transform: scale(0.98);
}

.copy-markdown-btn svg {
    width: 18px;
    height: 18px;
    flex-shrink: 0;
}

.copy-markdown-btn.success {
    background-color: #10b981;
    border-color: #10b981;
    color: white;
}

.copy-markdown-btn.error {
    background-color: #ef4444;
    border-color: #ef4444;
    color: white;
}

.copy-markdown-btn.success:hover,
.copy-markdown-btn.error:hover {
    background-color: var(--bg-secondary);
    border-color: var(--border);
    color: var(--text-primary);
}

.post-content {
    font-size: 1.125rem;
    line-height: 1.8;
}

.post-content h1,
.post-content h2,
.post-content h3,
.post-content h4,
.post-content h5,
.post-content h6 {
    margin-top: var(--spacing-xl);
    margin-bottom: var(--spacing-md);
}

.post-content h1:first-child,
.post-content h2:first-child,
.post-content h3:first-child {
    margin-top: 0;
}

.post-content img {
    max-width: 100%;
    height: auto;
    border-radius: 8px;
    margin: var(--spacing-lg) 0;
}

.post-content pre {
    background-color: var(--code-bg);
    border: 1px solid var(--code-border);
    border-radius: 8px;
    padding: var(--spacing-md);
    overflow-x: auto;
    margin: var(--spacing-lg) 0;
}

.post-content code {
    font-family: var(--font-mono);
    font-size: 0.9em;
    background-color: var(--code-bg);
    padding: 0.2em 0.4em;
    border-radius: 4px;
    border: 1px solid var(--code-border);
}

.post-content pre code {
    background: none;
    border: none;
    padding: 0;
}

.post-content blockquote {
    border-left: 4px solid var(--accent);
    padding-left: var(--spacing-md);
    margin: var(--spacing-lg) 0;
    color: var(--text-secondary);
    font-style: italic;
}

.post-content ul,
.post-content ol {
    margin-bottom: var(--spacing-md);
    padding-left: var(--spacing-lg);
}

.post-content li {
    margin-bottom: var(--spacing-xs);
}

.post-content a {
    text-decoration: underline;
}

.post-content table {
    width: 100%;
    border-collapse: collapse;
    margin: var(--spacing-lg) 0;
}

.post-content th,
.post-content td {
    padding: var(--spacing-sm);
    border: 1px solid var(--border);
    text-align: left;
}

.post-content th {
    background-color: var(--bg-secondary);
    font-weight: 600;
}

.post-footer {
    margin-top: var(--spacing-xl);
    padding-top: var(--spacing-lg);
    border-top: 1px solid var(--border);
}

/* ===== Footer ===== */
.site-footer {
    background-color: var(--bg-secondary);
    border-top: 1px solid var(--border);
    padding: var(--spacing-xl) 0;
    margin-top: var(--spacing-xl);
    text-align: center;
}

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

.site-footer p:last-child {
    margin-bottom: 0;
}

.footer-links {
    display: flex;
    gap: var(--spacing-md);
    justify-content: center;
}

.footer-links a {
    color: var(--text-secondary);
}

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

/* ===== Utility Classes ===== */
.loading {
    text-align: center;
    color: var(--text-secondary);
    padding: var(--spacing-xl);
}

/* ===== Back to Top Button ===== */
.back-to-top {
    position: fixed;
    bottom: 2rem;
    right: 2rem;
    width: 48px;
    height: 48px;
    border-radius: 50%;
    background-color: var(--accent);
    color: white;
    border: none;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    box-shadow: 0 4px 12px var(--shadow);
    transition: all 0.3s ease;
    opacity: 0;
    visibility: hidden;
    z-index: 99;
}

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

.back-to-top:hover {
    background-color: var(--accent-hover);
    transform: translateY(-4px);
    box-shadow: 0 6px 16px var(--shadow);
}

.back-to-top:active {
    transform: translateY(-2px);
}

.back-to-top svg {
    width: 24px;
    height: 24px;
}

/* ===== Responsive Design ===== */
@media (max-width: 768px) {
    :root {
        --spacing-xl: 2rem;
        --spacing-lg: 1.5rem;
    }

    h1 { font-size: 2rem; }
    h2 { font-size: 1.75rem; }
    h3 { font-size: 1.5rem; }

    .hero h2 {
        font-size: 2rem;
    }

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

    .post-title {
        font-size: 2rem;
    }

    .post-content {
        font-size: 1rem;
    }

    .nav {
        gap: var(--spacing-sm);
    }

    .post-card-meta {
        flex-direction: column;
        gap: var(--spacing-xs);
    }

    .post-meta {
        flex-wrap: wrap;
    }

    .post-meta-left {
        flex-direction: column;
        gap: var(--spacing-xs);
        align-items: flex-start;
    }

    .copy-markdown-btn {
        font-size: 0.8rem;
        padding: var(--spacing-xs) var(--spacing-sm);
    }
}

@media (max-width: 480px) {
    html {
        font-size: 14px;
    }

    .container,
    .container-narrow {
        padding: 0 var(--spacing-sm);
    }

    .site-header {
        padding: var(--spacing-sm) 0;
    }

    .post-card {
        padding: var(--spacing-md);
    }

    .back-to-top {
        bottom: 1rem;
        right: 1rem;
        width: 44px;
        height: 44px;
    }

    .back-to-top svg {
        width: 20px;
        height: 20px;
    }

    .copy-markdown-btn .copy-btn-text {
        display: none;
    }

    .copy-markdown-btn {
        padding: var(--spacing-xs);
        width: 36px;
        height: 36px;
        justify-content: center;
    }

    .copy-markdown-btn svg {
        width: 16px;
        height: 16px;
    }
}

/* ===== About Page Styles ===== */
.about-section {
    margin-bottom: var(--spacing-xl);
}

.about-section h2 {
    font-size: 1.75rem;
    margin-bottom: var(--spacing-md);
    color: var(--text-primary);
    border-bottom: 2px solid var(--border);
    padding-bottom: var(--spacing-sm);
}

.about-section h3 {
    font-size: 1.25rem;
    margin-bottom: var(--spacing-sm);
    color: var(--text-primary);
}

.about-section p {
    color: var(--text-primary);
    margin-bottom: var(--spacing-md);
}

.skills-container {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: var(--spacing-md);
    margin-top: var(--spacing-md);
}

.skill-category {
    background-color: var(--bg-secondary);
    border: 1px solid var(--border);
    border-radius: 8px;
    padding: var(--spacing-md);
}

.skill-category h3 {
    font-size: 1rem;
    margin-bottom: var(--spacing-sm);
    color: var(--accent);
}

.skill-category p {
    color: var(--text-secondary);
    margin-bottom: 0;
    font-size: 0.9rem;
    line-height: 1.6;
}

.experience-item {
    margin-bottom: var(--spacing-lg);
    padding: var(--spacing-md);
    background-color: var(--bg-secondary);
    border-left: 4px solid var(--accent);
    border-radius: 4px;
}

.experience-item:last-child {
    margin-bottom: 0;
}

.experience-header {
    display: flex;
    justify-content: space-between;
    align-items: baseline;
    flex-wrap: wrap;
    gap: var(--spacing-sm);
    margin-bottom: var(--spacing-xs);
}

.experience-header h3 {
    font-size: 1.25rem;
    margin-bottom: 0;
}

.experience-period {
    color: var(--text-secondary);
    font-size: 0.875rem;
    font-weight: 500;
}

.experience-role {
    color: var(--text-secondary);
    font-size: 0.95rem;
    margin-bottom: 0;
}

.links-list {
    list-style: none;
    padding: 0;
}

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

.links-list li:last-child {
    margin-bottom: 0;
}

.links-list a {
    display: inline-flex;
    align-items: center;
    color: var(--accent);
    font-weight: 500;
    transition: color 0.2s ease;
}

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

.links-list a::before {
    content: '→';
    margin-right: var(--spacing-xs);
    font-weight: bold;
}

/* ===== Print Styles ===== */
@media print {
    .site-header,
    .site-footer,
    .back-link,
    .theme-toggle,
    .post-footer {
        display: none;
    }

    body {
        background: white;
        color: black;
    }

    .post-content a {
        color: black;
        text-decoration: underline;
    }
}