/* ===== CSS Variables ===== */
:root {
    --bg-primary: #0a0a0a;
    --bg-secondary: #111111;
    --text-primary: #e0e0e0;
    --text-secondary: #a0a0a0;
    --accent: #64b5f6;
    --accent-hover: #90caf9;
    --border: #2a2a2a;
    
    --font-sans: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
    --font-mono: 'SF Mono', 'Fira Code', 'Consolas', monospace;
    
    --max-width: 680px;
    --transition: 0.2s ease;
}

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

html {
    font-size: 16px;
    scroll-behavior: smooth;
}

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

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

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

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

.navbar {
    max-width: var(--max-width);
    margin: 0 auto;
    padding: 1rem 1.5rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.nav-brand a {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-size: 1.25rem;
    font-weight: 600;
    color: var(--text-primary);
    position: relative;
}

.brand-icon {
    color: var(--accent);
    flex-shrink: 0;
}

.nav-brand a::after {
    content: '';
    position: absolute;
    bottom: -4px;
    left: 0;
    width: 0;
    height: 2px;
    background-color: var(--accent);
    transition: width var(--transition);
}

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

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

.nav-links a {
    display: flex;
    align-items: center;
    gap: 0.35rem;
    color: var(--text-secondary);
    font-size: 0.9rem;
    position: relative;
}

.external-icon {
    opacity: 0.6;
    transition: opacity var(--transition);
}

.nav-links a:hover .external-icon {
    opacity: 1;
}

.nav-links a::after {
    content: '';
    position: absolute;
    bottom: -4px;
    left: 0;
    width: 0;
    height: 2px;
    background-color: var(--accent);
    transition: width var(--transition);
}

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

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

/* ===== Main Container ===== */
.container {
    max-width: var(--max-width);
    margin: 0 auto;
    padding: 2rem 1.5rem;
    flex: 1;
}

/* ===== Page Title ===== */
.page-title {
    font-size: 1.75rem;
    font-weight: 600;
    color: var(--text-primary);
    margin: 0;
}

/* ===== List Header ===== */
.list-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 2rem;
    gap: 1rem;
    flex-wrap: wrap;
}

/* ===== Tag Dropdown ===== */
.tag-dropdown {
    position: relative;
}

.tag-dropdown-btn {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.5rem 1rem;
    background-color: var(--bg-secondary);
    border: 1px solid var(--border);
    border-radius: 6px;
    color: var(--text-secondary);
    font-size: 0.9rem;
    cursor: pointer;
    transition: all var(--transition);
    font-family: inherit;
}

.tag-dropdown-btn:hover {
    border-color: var(--accent);
    color: var(--text-primary);
}

.tag-dropdown-btn svg {
    transition: transform var(--transition);
}

.tag-dropdown.open .tag-dropdown-btn {
    border-color: var(--accent);
    color: var(--text-primary);
}

.tag-dropdown.open .tag-dropdown-btn svg {
    transform: rotate(180deg);
}

.tag-dropdown-menu {
    position: absolute;
    top: calc(100% + 0.5rem);
    right: 0;
    min-width: 180px;
    max-height: 0;
    overflow: hidden;
    background-color: var(--bg-secondary);
    border: 1px solid var(--border);
    border-radius: 8px;
    opacity: 0;
    visibility: hidden;
    transition: all 0.2s ease;
    z-index: 100;
}

.tag-dropdown.open .tag-dropdown-menu {
    max-height: 220px;
    overflow-y: auto;
    opacity: 1;
    visibility: visible;
}

.tag-dropdown-menu::-webkit-scrollbar {
    width: 6px;
}

.tag-dropdown-menu::-webkit-scrollbar-track {
    background: var(--bg-primary);
}

.tag-dropdown-menu::-webkit-scrollbar-thumb {
    background-color: var(--border);
    border-radius: 3px;
}

.tag-dropdown-menu::-webkit-scrollbar-thumb:hover {
    background-color: var(--text-secondary);
}

.dropdown-tag {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0.6rem 1rem;
    color: var(--text-secondary);
    font-size: 0.85rem;
    border-bottom: 1px solid var(--border);
    transition: all var(--transition);
}

.dropdown-tag:last-child {
    border-bottom: none;
}

.dropdown-tag:hover {
    background-color: rgba(100, 181, 246, 0.1);
    color: var(--accent);
}

.dropdown-tag.active {
    background-color: rgba(100, 181, 246, 0.15);
    color: var(--accent);
}

.dropdown-tag .tag-count {
    font-size: 0.75rem;
    color: var(--text-secondary);
}

/* ===== Blog List ===== */
.blog-list {
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

.post-card {
    background-color: var(--bg-secondary);
    border: 1px solid var(--border);
    border-radius: 8px;
    overflow: hidden;
    transition: border-color var(--transition);
}

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

.post-card .post-header {
    padding: 1.25rem 1.5rem;
    cursor: pointer;
    transition: background-color var(--transition);
}

.post-card .post-header:hover {
    background-color: rgba(100, 181, 246, 0.05);
}

.post-card .post-title {
    font-size: 1.25rem;
    font-weight: 500;
    color: var(--text-primary);
    margin-bottom: 0.5rem;
    transition: color var(--transition);
}

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

.post-meta {
    display: flex;
    flex-wrap: wrap;
    gap: 0.75rem;
    align-items: center;
    font-size: 0.85rem;
    color: var(--text-secondary);
}

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

.tag {
    color: var(--accent);
    font-size: 0.8rem;
    padding: 0.15rem 0.5rem;
    background-color: rgba(100, 181, 246, 0.1);
    border-radius: 4px;
    transition: background-color var(--transition), color var(--transition);
}

.tag:hover {
    background-color: rgba(100, 181, 246, 0.2);
    color: var(--accent-hover);
}

/* ===== Post Summary (Expandable) ===== */
.post-summary {
    max-height: 0;
    overflow: hidden;
    transition: max-height 0.3s ease, padding 0.3s ease;
    padding: 0 1.5rem;
    border-top: 0 solid var(--border);
}

.post-summary.expanded {
    max-height: 500px;
    padding: 1.25rem 1.5rem;
    border-top: 1px solid var(--border);
}

.summary-content {
    color: var(--text-secondary);
    margin-bottom: 1rem;
    line-height: 1.6;
}

.read-more {
    display: inline-block;
    font-size: 0.9rem;
    font-weight: 500;
    color: var(--accent);
    transition: color var(--transition);
}

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

/* ===== Single Post ===== */
.single-post {
    max-width: var(--max-width);
}

.single-post .post-header {
    margin-bottom: 2rem;
    padding-bottom: 1.5rem;
    border-bottom: 1px solid var(--border);
}

.single-post .post-title {
    font-size: 2rem;
    font-weight: 600;
    line-height: 1.3;
    margin-bottom: 1rem;
}

.post-content {
    font-size: 1rem;
    line-height: 1.8;
}

.post-content h2 {
    font-size: 1.5rem;
    margin: 2rem 0 1rem;
    color: var(--text-primary);
}

.post-content h3 {
    font-size: 1.25rem;
    margin: 1.5rem 0 0.75rem;
    color: var(--text-primary);
}

.post-content p {
    margin-bottom: 1.25rem;
    color: var(--text-primary);
}

.post-content ul, .post-content ol {
    margin-bottom: 1.25rem;
    padding-left: 1.5rem;
}

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

.post-content code {
    font-family: var(--font-mono);
    font-size: 0.9em;
    background-color: var(--bg-secondary);
    padding: 0.15rem 0.4rem;
    border-radius: 4px;
    border: 1px solid var(--border);
}

.post-content pre {
    background-color: var(--bg-secondary);
    border: 1px solid var(--border);
    border-radius: 8px;
    padding: 1rem 1.25rem;
    overflow-x: auto;
    margin-bottom: 1.25rem;
}

.post-content pre code {
    background: none;
    border: none;
    padding: 0;
    font-size: 0.85rem;
    line-height: 1.6;
}

.post-content blockquote {
    border-left: 3px solid var(--accent);
    padding-left: 1rem;
    margin: 1.5rem 0;
    color: var(--text-secondary);
    font-style: italic;
}

.post-content img {
    max-width: 100%;
    height: auto;
    border-radius: 8px;
    margin: 1.5rem 0;
}

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

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

/* ===== Post Navigation ===== */
.post-navigation {
    display: flex;
    justify-content: space-between;
    gap: 1rem;
    margin-top: 3rem;
    padding-top: 2rem;
    border-top: 1px solid var(--border);
}

.nav-link {
    flex: 1;
    padding: 1rem;
    background-color: var(--bg-secondary);
    border: 1px solid var(--border);
    border-radius: 8px;
    transition: border-color var(--transition), background-color var(--transition);
}

.nav-link:hover {
    border-color: var(--accent);
    background-color: rgba(100, 181, 246, 0.05);
}

.nav-link.nav-disabled {
    visibility: hidden;
}

.nav-older {
    text-align: right;
}

.nav-newer {
    text-align: left;
}

.nav-label {
    display: block;
    font-size: 0.8rem;
    color: var(--text-secondary);
    margin-bottom: 0.25rem;
}

.nav-title {
    display: block;
    font-size: 0.95rem;
    color: var(--text-primary);
    font-weight: 500;
}

/* ===== Tags Page ===== */
.tags-cloud {
    display: flex;
    flex-wrap: wrap;
    gap: 0.75rem;
    margin-bottom: 2rem;
}

.tag-cloud-item {
    padding: 0.5rem 1rem;
    background-color: var(--bg-secondary);
    border: 1px solid var(--border);
    border-radius: 20px;
    font-size: 0.9rem;
    transition: border-color var(--transition), background-color var(--transition);
}

.tag-cloud-item:hover {
    border-color: var(--accent);
    background-color: rgba(100, 181, 246, 0.1);
}

.tag-count {
    color: var(--text-secondary);
    font-size: 0.8rem;
}

.back-link {
    display: inline-block;
    margin-top: 2rem;
    color: var(--text-secondary);
    font-size: 0.9rem;
}

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

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

.footer-content {
    max-width: var(--max-width);
    margin: 0 auto;
    padding: 1.5rem;
    text-align: center;
}

.footer-content p {
    color: var(--text-secondary);
    font-size: 0.85rem;
}

/* ===== No Posts Message ===== */
.no-posts {
    text-align: center;
    color: var(--text-secondary);
    padding: 3rem 0;
}

/* ===== Responsive ===== */
@media (max-width: 600px) {
    .navbar {
        padding: 0.75rem 1rem;
    }
    
    .nav-brand a {
        font-size: 1.1rem;
    }
    
    .nav-links {
        gap: 1rem;
    }
    
    .nav-links a {
        font-size: 0.85rem;
    }
    
    .container {
        padding: 1.5rem 1rem;
    }
    
    .list-header {
        flex-direction: row;
        align-items: center;
        justify-content: space-between;
    }
    
    .tag-dropdown-menu {
        right: 0;
        left: auto;
    }
    
    .page-title {
        font-size: 1.5rem;
    }
    
    .post-card .post-header {
        padding: 1rem;
    }
    
    .post-card .post-title {
        font-size: 1.1rem;
    }
    
    .post-summary.expanded {
        padding: 1rem;
    }
    
    .single-post .post-title {
        font-size: 1.5rem;
    }
    
    .post-navigation {
        flex-direction: column;
    }
    
    .nav-older, .nav-newer {
        text-align: left;
    }
}