/* ===== CSS Variables ===== */
:root {
    --color-bg: #1a1a2e;
    --color-bg-secondary: #16213e;
    --color-text: #eaeaea;
    --color-text-muted: #a0a0a0;
    --color-primary: #0f9b8e;
    --color-primary-hover: #0cc0b0;
    --color-link: #64b5f6;
    --color-link-hover: #90caf9;
    --color-border: #2d2d44;
    --color-code-bg: #0d1117;
    --color-tag-bg: #2d2d44;
    
    --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    --font-mono: 'JetBrains Mono', 'Fira Code', Consolas, monospace;
    
    --max-width: 800px;
    --spacing: 1.5rem;
}

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

/* ===== Base ===== */
html {
    font-size: 16px;
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-sans);
    background-color: var(--color-bg);
    color: var(--color-text);
    line-height: 1.7;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

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

/* ===== Typography ===== */
h1, h2, h3, h4, h5, h6 {
    line-height: 1.3;
    margin-top: 2rem;
    margin-bottom: 1rem;
    font-weight: 600;
}

h1 { font-size: 2.25rem; }
h2 { font-size: 1.75rem; }
h3 { font-size: 1.5rem; }
h4 { font-size: 1.25rem; }

p {
    margin-bottom: 1rem;
}

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

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

/* ===== Header ===== */
.site-header {
    background-color: var(--color-bg-secondary);
    border-bottom: 1px solid var(--color-border);
    padding: 1rem 0;
    position: sticky;
    top: 0;
    z-index: 100;
}

.site-header .container {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.site-title {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--color-primary);
}

.site-title:hover {
    color: var(--color-primary-hover);
    text-decoration: none;
}

.site-nav {
    display: flex;
    gap: 1.5rem;
}

.site-nav a {
    color: var(--color-text-muted);
    font-weight: 500;
}

.site-nav a:hover {
    color: var(--color-text);
    text-decoration: none;
}

/* ===== Main Content ===== */
.site-main {
    flex: 1;
    padding: 3rem 0;
}

/* ===== Hero Section ===== */
.hero {
    text-align: center;
    margin-bottom: 3rem;
    padding-bottom: 2rem;
    border-bottom: 1px solid var(--color-border);
}

.hero h1 {
    font-size: 2.5rem;
    margin-top: 0;
    color: var(--color-primary);
}

.site-description {
    font-size: 1.2rem;
    color: var(--color-text-muted);
}

/* ===== Post List ===== */
.post-list {
    list-style: none;
}

.post-item {
    padding: 1.5rem 0;
    border-bottom: 1px solid var(--color-border);
}

.post-item:last-child {
    border-bottom: none;
}

.post-item h2,
.post-item h3 {
    margin-top: 0;
    margin-bottom: 0.5rem;
}

.post-item h2 a,
.post-item h3 a {
    color: var(--color-text);
}

.post-item h2 a:hover,
.post-item h3 a:hover {
    color: var(--color-primary);
    text-decoration: none;
}

.post-meta {
    font-size: 0.9rem;
    color: var(--color-text-muted);
    margin-bottom: 0.75rem;
    display: flex;
    gap: 1rem;
    flex-wrap: wrap;
}

.post-excerpt {
    color: var(--color-text-muted);
    margin-bottom: 0.75rem;
}

.post-tags {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
}

.tag {
    background-color: var(--color-tag-bg);
    padding: 0.25rem 0.75rem;
    border-radius: 1rem;
    font-size: 0.85rem;
    color: var(--color-text-muted);
}

.tag:hover {
    background-color: var(--color-primary);
    color: var(--color-text);
    text-decoration: none;
}

.view-all {
    margin-top: 2rem;
    text-align: center;
}

/* ===== Single Post ===== */
.post-header {
    margin-bottom: 2rem;
    padding-bottom: 1rem;
    border-bottom: 1px solid var(--color-border);
}

.post-title {
    font-size: 2.5rem;
    margin-top: 0;
}

.post-content {
    line-height: 1.8;
}

.post-content h2,
.post-content h3,
.post-content h4 {
    scroll-margin-top: 4rem;
}

.post-content img {
    max-width: 100%;
    height: auto;
    border-radius: 0.5rem;
}

.post-content blockquote {
    border-left: 4px solid var(--color-primary);
    padding-left: 1rem;
    margin: 1.5rem 0;
    color: var(--color-text-muted);
    font-style: italic;
}

.post-content ul,
.post-content ol {
    margin: 1rem 0;
    padding-left: 2rem;
}

.post-content li {
    margin-bottom: 0.5rem;
}

.post-content table {
    width: 100%;
    border-collapse: collapse;
    margin: 1.5rem 0;
}

.post-content th,
.post-content td {
    padding: 0.75rem;
    border: 1px solid var(--color-border);
    text-align: left;
}

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

/* ===== Code Blocks ===== */
.post-content code {
    font-family: var(--font-mono);
    font-size: 0.9em;
    background-color: var(--color-code-bg);
    padding: 0.2rem 0.4rem;
    border-radius: 0.25rem;
}

.post-content pre {
    margin: 1.5rem 0;
    border-radius: 0.5rem;
    overflow-x: auto;
}

.post-content pre code {
    display: block;
    padding: 1rem;
    background: transparent;
}

.code-block {
    background-color: var(--color-code-bg);
    border-radius: 0.5rem;
    margin: 1.5rem 0;
    overflow: hidden;
}

.code-header {
    background-color: rgba(255, 255, 255, 0.05);
    padding: 0.5rem 1rem;
    font-size: 0.85rem;
    color: var(--color-text-muted);
    font-family: var(--font-mono);
}

.code-block pre {
    margin: 0;
    padding: 1rem;
}

/* ===== Math Blocks ===== */
.math-block {
    overflow-x: auto;
    padding: 1rem 0;
    text-align: center;
}

/* ===== TOC ===== */
.toc {
    background-color: var(--color-bg-secondary);
    border-radius: 0.5rem;
    padding: 1.5rem;
    margin-bottom: 2rem;
}

.toc h2 {
    font-size: 1.1rem;
    margin-top: 0;
    margin-bottom: 1rem;
}

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

.toc li {
    margin-bottom: 0.5rem;
}

.toc-level-2 { padding-left: 0; }
.toc-level-3 { padding-left: 1rem; }
.toc-level-4 { padding-left: 2rem; }

.toc a {
    color: var(--color-text-muted);
}

.toc a:hover {
    color: var(--color-text);
}

/* ===== Post Footer ===== */
.post-footer {
    margin-top: 3rem;
    padding-top: 2rem;
    border-top: 1px solid var(--color-border);
}

.post-nav {
    display: flex;
    justify-content: space-between;
}

/* ===== Tags Cloud ===== */
.tags-cloud {
    margin-top: 3rem;
    padding-top: 2rem;
    border-top: 1px solid var(--color-border);
}

.tags {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
}

/* ===== Archive ===== */
.archive h1 {
    margin-top: 0;
}

/* ===== Footer ===== */
.site-footer {
    background-color: var(--color-bg-secondary);
    border-top: 1px solid var(--color-border);
    padding: 2rem 0;
    text-align: center;
    color: var(--color-text-muted);
    font-size: 0.9rem;
}

.site-footer p {
    margin-bottom: 0.5rem;
}

.site-footer a {
    color: var(--color-text-muted);
}

.site-footer a:hover {
    color: var(--color-text);
}

/* ===== Responsive ===== */
@media (max-width: 640px) {
    :root {
        --spacing: 1rem;
    }
    
    h1 { font-size: 1.75rem; }
    h2 { font-size: 1.5rem; }
    
    .hero h1 {
        font-size: 2rem;
    }
    
    .post-title {
        font-size: 1.75rem;
    }
    
    .site-header .container {
        flex-direction: column;
        gap: 1rem;
    }
    
    .site-nav {
        gap: 1rem;
    }
}