/* ===== RESET & BASE ===== */
html {
    scroll-behavior: smooth;
    scroll-padding-top: 100px;
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

::selection {
    background-color: #a78bfa;
    color: #ffffff;
}

::-moz-selection {
    background-color: #a78bfa;
    color: #ffffff;
}

/* ===== CSS VARIABLES ===== */
:root {
    --bg-primary: #ffffff;
    --bg-secondary: rgba(0, 0, 0, 0.02);
    --bg-nav: rgba(255, 255, 255, 0.85);
    --text-primary: #1a1a1a;
    --text-secondary: #666;
    --text-tertiary: #999;
    --text-brand: #000;
    --border-color: rgba(0, 0, 0, 0.08);
    --border-hover: rgba(0, 0, 0, 0.2);
    --grid-color: rgba(0, 0, 0, 0.03);
    --gradient-color-1: rgba(0, 0, 0, 0.02);
    --gradient-color-2: rgba(0, 0, 0, 0.03);
    --shadow-color: rgba(0, 0, 0, 0.08);
    --glass-bg: rgba(0, 0, 0, 0.02);
    --glass-hover: rgba(0, 0, 0, 0.04);
    --accent-color: #a78bfa;
    --accent-hover: #8b5cf6;
    --code-bg: rgba(0, 0, 0, 0.05);
    --code-block-bg: #f5f7fb;
    --code-inline-text: #111111;
    --code-block-text: #111111;
    --scrollbar-color: rgba(0, 0, 0, 0.2);
}

[data-theme="dark"] {
    --bg-primary: #0a0a0a;
    --bg-secondary: rgba(255, 255, 255, 0.05);
    --bg-nav: rgba(10, 10, 10, 0.85);
    --text-primary: #e5e5e5;
    --text-secondary: #a3a3a3;
    --text-tertiary: #737373;
    --text-brand: #fff;
    --border-color: rgba(255, 255, 255, 0.1);
    --border-hover: rgba(255, 255, 255, 0.3);
    --grid-color: rgba(255, 255, 255, 0.03);
    --gradient-color-1: rgba(167, 139, 250, 0.05);
    --gradient-color-2: rgba(139, 92, 246, 0.08);
    --shadow-color: rgba(0, 0, 0, 0.5);
    --glass-bg: rgba(255, 255, 255, 0.03);
    --glass-hover: rgba(255, 255, 255, 0.06);
    --code-bg: rgba(255, 255, 255, 0.05);
    --code-block-bg: rgba(255, 255, 255, 0.03);
    --code-inline-text: #e5e5e5;
    --code-block-text: #e5e5e5;
    --scrollbar-color: rgba(255, 255, 255, 0.2);
}

/* ===== BODY & BACKGROUNDS ===== */
body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    background: var(--bg-primary);
    color: var(--text-primary);
    min-height: 100vh;
    overflow-x: hidden;
    line-height: 1.6;
    transition: background 0.3s ease, color 0.3s ease;
}

.bg-grid {
    position: fixed;
    width: 100%;
    height: 100%;
    top: 0;
    left: 0;
    z-index: -2;
    opacity: 0.4;
    background-image: 
        linear-gradient(var(--grid-color) 1px, transparent 1px),
        linear-gradient(90deg, var(--grid-color) 1px, transparent 1px);
    background-size: 50px 50px;
    pointer-events: none;
}

.bg-gradient {
    position: fixed;
    width: 100%;
    height: 100%;
    top: 0;
    left: 0;
    z-index: -1;
    opacity: 0.6;
    background: radial-gradient(circle at 20% 20%, var(--gradient-color-1) 0%, transparent 50%),
                radial-gradient(circle at 80% 80%, var(--gradient-color-2) 0%, transparent 50%);
    pointer-events: none;
}

/* ===== NAVIGATION ===== */
.nav {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 1000;
    background: var(--bg-nav);
    backdrop-filter: blur(20px);
    border-bottom: 1px solid var(--border-color);
    transition: all 0.3s ease;
}

.nav-container {
    max-width: 1400px;
    margin: 0 auto;
    padding: 1rem 2rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.nav-brand {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--text-brand);
    text-decoration: none;
    transition: opacity 0.2s ease;
}

.nav-brand:hover {
    opacity: 0.7;
}

.theme-toggle {
    background: var(--glass-bg);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    padding: 0.5rem;
    cursor: pointer;
    color: var(--text-primary);
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all 0.2s ease;
}

.theme-toggle:hover {
    background: var(--glass-hover);
    border-color: var(--border-hover);
}

.sun-icon {
    display: none;
}

.moon-icon {
    display: block;
}

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

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

/* ===== MAIN CONTAINER ===== */
#app {
    min-height: 100vh;
    padding-top: 80px;
}

.container {
    max-width: 1400px;
    margin: 0 auto;
    padding: 2rem;
}

/* ===== LOADING & ERROR STATES ===== */
.loading-skeleton {
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
    animation: pulse 1.5s ease-in-out infinite;
}

@keyframes pulse {
    0%, 100% { opacity: 1; }
    50% { opacity: 0.5; }
}

.skeleton-card {
    background: var(--glass-bg);
    border: 1px solid var(--border-color);
    border-radius: 16px;
    height: 200px;
}

.error-state {
    text-align: center;
    padding: 4rem 2rem;
}

.error-state h2 {
    font-size: 2rem;
    margin-bottom: 1rem;
    color: var(--text-primary);
}

.error-state p {
    color: var(--text-secondary);
    margin-bottom: 2rem;
}

.btn {
    display: inline-block;
    padding: 0.75rem 1.5rem;
    background: var(--glass-bg);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    color: var(--text-primary);
    text-decoration: none;
    font-weight: 500;
    transition: all 0.2s ease;
    cursor: pointer;
    font-size: 0.95rem;
}

.btn:hover {
    background: var(--glass-hover);
    border-color: var(--border-hover);
    transform: translateY(-2px);
}

.btn-primary {
    background: var(--accent-color);
    border-color: var(--accent-color);
    color: #fff;
}

.btn-primary:hover {
    background: var(--accent-hover);
    border-color: var(--accent-hover);
}

/* ===== HOME PAGE ===== */
.home-header {
    margin-bottom: 3rem;
}

.home-header h1 {
    font-size: 2.5rem;
    font-weight: 800;
    margin-bottom: 0.5rem;
    background: linear-gradient(135deg, var(--text-primary), var(--accent-color));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.home-header p {
    color: var(--text-secondary);
    font-size: 1.1rem;
}

/* Search & Filters */
.filters-container {
    margin-bottom: 2rem;
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

.search-box {
    position: relative;
}

.search-box input {
    width: 100%;
    padding: 0.875rem 1rem 0.875rem 3rem;
    background: var(--glass-bg);
    border: 1px solid var(--border-color);
    border-radius: 12px;
    color: var(--text-primary);
    font-size: 0.95rem;
    transition: all 0.2s ease;
    font-family: inherit;
}

.search-box input:focus {
    outline: none;
    border-color: var(--accent-color);
    background: var(--bg-secondary);
}

.search-icon {
    position: absolute;
    left: 1rem;
    top: 50%;
    transform: translateY(-50%);
    color: var(--text-secondary);
    pointer-events: none;
}

.filter-chips {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
    align-items: center;
}

/* Make the chips containers behave like a row of chips */
#tagChips,
#difficultyChips {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  align-items: center;
}


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

.chip {
    padding: 0.5rem 1rem;
    background: var(--glass-bg);
    border: 1px solid var(--border-color);
    border-radius: 20px;
    color: var(--text-secondary);
    font-size: 0.875rem;
    cursor: pointer;
    transition: all 0.2s ease;
    user-select: none;
}

.chip:hover {
    background: var(--glass-hover);
    border-color: var(--border-hover);
}

.chip.active {
    background: var(--accent-color);
    border-color: var(--accent-color);
    color: #fff;
}

.difficulty-chip {
    display: flex;
    align-items: center;
    gap: 0.25rem;
}

.difficulty-dot {
    width: 6px;
    height: 6px;
    border-radius: 50%;
}

.difficulty-dot.easy { background: #10b981; }
.difficulty-dot.medium { background: #f59e0b; }
.difficulty-dot.hard { background: #ef4444; }

/* Writeup Cards Grid */
.writeups-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
    gap: 1.5rem;
}

.writeup-card {
    background: var(--glass-bg);
    backdrop-filter: blur(20px);
    border: 1px solid var(--border-color);
    border-radius: 16px;
    overflow: hidden;
    transition: all 0.3s ease;
    cursor: pointer;
    display: flex;
    flex-direction: column;
}

.writeup-card:hover {
    transform: translateY(-4px);
    border-color: var(--border-hover);
    box-shadow: 0 12px 40px var(--shadow-color);
}

.card-cover {
    width: 100%;
    height: 180px;
    object-fit: cover;
    background: var(--bg-secondary);
}

.card-content {
    padding: 1.5rem;
    flex: 1;
    display: flex;
    flex-direction: column;
}

.card-meta {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    margin-bottom: 0.75rem;
    font-size: 0.8rem;
    color: var(--text-tertiary);
}

.card-meta .difficulty-badge {
    display: flex;
    align-items: center;
    gap: 0.25rem;
    padding: 0.25rem 0.5rem;
    background: var(--bg-secondary);
    border-radius: 4px;
}

.card-title {
    font-size: 1.25rem;
    font-weight: 700;
    margin-bottom: 0.5rem;
    color: var(--text-primary);
}

.card-summary {
    color: var(--text-secondary);
    font-size: 0.9rem;
    margin-bottom: 1rem;
    flex: 1;
    line-height: 1.5;
}

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

.tag {
    padding: 0.25rem 0.75rem;
    background: var(--bg-secondary);
    border-radius: 12px;
    font-size: 0.75rem;
    color: var(--text-secondary);
    transition: all 0.2s ease;
}

.tag:hover {
    background: var(--accent-color);
    color: #fff;
}

.no-results {
    text-align: center;
    padding: 4rem 2rem;
    color: var(--text-secondary);
}

.no-results h3 {
    font-size: 1.5rem;
    margin-bottom: 0.5rem;
    color: var(--text-primary);
}

/* ===== WRITEUP PAGE ===== */
.writeup-layout {
    display: grid;
    grid-template-columns: 280px 1fr;
    gap: 3rem;
    max-width: 1400px;
    margin: 0 auto;
    padding: 2rem;
}

.sidebar {
    position: sticky;
    top: 100px;
    height: fit-content;
    max-height: calc(100vh - 120px);
    overflow-y: auto;
}

.sidebar-section {
    margin-bottom: 2rem;
}

.sidebar-title {
    font-size: 0.75rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    color: var(--text-tertiary);
    margin-bottom: 1rem;
}

.back-link {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    color: var(--text-secondary);
    text-decoration: none;
    font-size: 0.9rem;
    padding: 0.5rem;
    border-radius: 8px;
    transition: all 0.2s ease;
}

.back-link:hover {
    background: var(--glass-hover);
    color: var(--text-primary);
}

.meta-item {
    display: flex;
    align-items: flex-start;
    gap: 0.5rem;
    padding: 0.5rem;
    font-size: 0.875rem;
    color: var(--text-secondary);
}

.meta-item svg {
    flex-shrink: 0;
    margin-top: 0.125rem;
}

.meta-tags {
    display: flex;
    flex-wrap: wrap;
    gap: 0.375rem;
}

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

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

.toc-link {
    display: block;
    color: var(--text-secondary);
    text-decoration: none;
    font-size: 0.875rem;
    padding: 0.375rem 0.75rem;
    border-left: 2px solid var(--border-color);
    transition: all 0.2s ease;
}

.toc-link:hover {
    color: var(--text-primary);
    border-left-color: var(--accent-color);
    padding-left: 1rem;
}

.toc-link.active {
    color: var(--accent-color);
    border-left-color: var(--accent-color);
    font-weight: 500;
}

.toc-link.level-3 {
    padding-left: 1.5rem;
    font-size: 0.8rem;
}

/* Content Area */
.content-area {
    min-width: 0;
}

.content-header {
    margin-bottom: 3rem;
}

.content-header h1 {
    font-size: 2.5rem;
    font-weight: 800;
    margin-bottom: 1rem;
    line-height: 1.2;
}

.content-meta {
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    gap: 1rem;
    color: var(--text-secondary);
    font-size: 0.9rem;
}

.content-meta-item {
    display: flex;
    align-items: center;
    gap: 0.375rem;
}

.reading-time {
    color: var(--text-tertiary);
}

/* Markdown Content Styling */
.markdown-content {
    color: var(--text-primary);
    font-size: 1.05rem;
    line-height: 1.75;
}

.markdown-content > * {
    margin-bottom: 1.5rem;
}

.markdown-content h1,
.markdown-content h2,
.markdown-content h3,
.markdown-content h4,
.markdown-content h5,
.markdown-content h6 {
    font-weight: 700;
    line-height: 1.3;
    margin-top: 2.5rem;
    margin-bottom: 1rem;
    position: relative;
    scroll-margin-top: 100px;
}

.markdown-content h1 { font-size: 2.25rem; }
.markdown-content h2 { font-size: 1.875rem; }
.markdown-content h3 { font-size: 1.5rem; }
.markdown-content h4 { font-size: 1.25rem; }
.markdown-content h5 { font-size: 1.125rem; }
.markdown-content h6 { font-size: 1rem; }

.markdown-content h2::before,
.markdown-content h3::before {
    content: '';
    position: absolute;
    left: -1.5rem;
    top: 50%;
    transform: translateY(-50%);
    width: 4px;
    height: 60%;
    background: var(--accent-color);
    border-radius: 2px;
    opacity: 0;
    transition: opacity 0.2s ease;
}

.markdown-content h2:hover::before,
.markdown-content h3:hover::before {
    opacity: 1;
}

.markdown-content p {
    margin-bottom: 1.25rem;
}

.markdown-content a {
    color: var(--accent-color);
    text-decoration: none;
    border-bottom: 1px solid transparent;
    transition: border-color 0.2s ease;
}

.markdown-content a:hover {
    border-bottom-color: var(--accent-color);
}

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

.markdown-content em {
    font-style: italic;
}

.markdown-content code {
    font-family: 'JetBrains Mono', 'Courier New', monospace;
    font-size: 0.9em;
    padding: 0.2em 0.4em;
    background: var(--code-bg);
    border-radius: 4px;
    border: 1px solid var(--border-color);
    color: var(--code-inline-text);
}

.markdown-content pre {
    position: relative;
    background: var(--code-block-bg);
    backdrop-filter: blur(20px);
    border: 1px solid var(--border-color);
    border-radius: 12px;
    padding: 1.5rem;
    overflow-x: auto;
    margin: 1.5rem 0;
}

.markdown-content pre code {
    background: none;
    border: none;
    padding: 0;
    font-size: 0.9rem;
    line-height: 1.6;
    display: block;
    color: var(--code-block-text);
}

.markdown-content pre code.hljs {
    color: var(--code-block-text);
}

.code-block-wrapper {
    position: relative;
    margin: 1.5rem 0;
}

.code-copy-btn {
    position: absolute;
    top: 1rem;
    right: 1rem;
    padding: 0.5rem 0.75rem;
    background: var(--glass-bg);
    border: 1px solid var(--border-color);
    border-radius: 6px;
    color: var(--text-secondary);
    font-size: 0.75rem;
    cursor: pointer;
    display: flex;
    align-items: center;
    gap: 0.375rem;
    transition: all 0.2s ease;
    z-index: 10;
}

.code-copy-btn:hover {
    background: var(--glass-hover);
    color: var(--text-primary);
}

.code-copy-btn.copied {
    color: #10b981;
    border-color: #10b981;
}

.markdown-content ul,
.markdown-content ol {
    padding-left: 2rem;
    margin-bottom: 1.5rem;
}

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

.markdown-content li > ul,
.markdown-content li > ol {
    margin-top: 0.5rem;
    margin-bottom: 0.5rem;
}

.markdown-content blockquote {
    border-left: 4px solid var(--accent-color);
    padding: 1rem 1.5rem;
    margin: 1.5rem 0;
    background: var(--glass-bg);
    backdrop-filter: blur(20px);
    border-radius: 0 8px 8px 0;
    font-style: italic;
    color: var(--text-secondary);
}

.markdown-content blockquote p:last-child {
    margin-bottom: 0;
}

/* Callouts */
.markdown-content .callout {
    padding: 1rem 1.25rem;
    margin: 1.5rem 0;
    border-radius: 8px;
    border-left: 4px solid;
    background: var(--glass-bg);
    backdrop-filter: blur(20px);
}

.markdown-content .callout-note {
    border-left-color: #3b82f6;
}

.markdown-content .callout-tip {
    border-left-color: #10b981;
}

.markdown-content .callout-warning {
    border-left-color: #f59e0b;
}

.markdown-content .callout-title {
    font-weight: 600;
    margin-bottom: 0.5rem;
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.markdown-content .table-wrapper {
    width: 100%;
    margin: 1.5rem 0;
    overflow-x: auto;
    overflow-y: hidden;
    background: var(--glass-bg);
    backdrop-filter: blur(20px);
    border: 1px solid var(--border-color);
    border-radius: 8px;
}

.markdown-content table {
    width: 100%;
    min-width: 100%;
    border-collapse: collapse;
    background: transparent;
}

.markdown-content thead {
    background: var(--bg-secondary);
}

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

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

.markdown-content tr:last-child td {
    border-bottom: none;
}

.markdown-content img {
    max-width: 100%;
    height: auto;
    border-radius: 8px;
    margin: 1.5rem 0;
    cursor: pointer;
    transition: all 0.3s ease;
    border: 1px solid var(--border-color);
}

.markdown-content img:hover {
    transform: scale(1.02);
    box-shadow: 0 12px 40px var(--shadow-color);
}

.markdown-content .img-caption {
    text-align: center;
    font-size: 0.875rem;
    color: var(--text-tertiary);
    margin-top: -1rem;
    margin-bottom: 1.5rem;
    font-style: italic;
}

.markdown-content hr {
    border: none;
    border-top: 1px solid var(--border-color);
    margin: 2.5rem 0;
}

/* ===== LIGHTBOX ===== */
.lightbox {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(0, 0, 0, 0.95);
    backdrop-filter: blur(10px);
    z-index: 9999;
    display: none;
    align-items: center;
    justify-content: center;
    animation: fadeIn 0.2s ease;
}

.lightbox.active {
    display: flex;
}

@keyframes fadeIn {
    from { opacity: 0; }
    to { opacity: 1; }
}

.lightbox-content {
    position: relative;
    max-width: 90%;
    max-height: 90%;
    display: flex;
    flex-direction: column;
    align-items: center;
}

.lightbox-close {
    position: absolute;
    top: -50px;
    right: 0;
    background: var(--glass-bg);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    padding: 0.5rem;
    color: #fff;
    cursor: pointer;
    transition: all 0.2s ease;
}

.lightbox-close:hover {
    background: var(--glass-hover);
}

#lightbox-img {
    max-width: 100%;
    max-height: 80vh;
    object-fit: contain;
    border-radius: 8px;
}

.lightbox-caption {
    color: #fff;
    margin-top: 1rem;
    text-align: center;
    font-size: 0.9rem;
}

/* ===== TOAST NOTIFICATIONS ===== */
#toast-container {
    position: fixed;
    top: 100px;
    right: 40px;
    z-index: 10001;
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

.toast {
    background: var(--glass-bg);
    backdrop-filter: blur(20px);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    padding: 1rem 1.25rem;
    display: flex;
    align-items: center;
    gap: 0.75rem;
    box-shadow: 0 8px 32px var(--shadow-color);
    animation: slideInRight 0.3s ease;
    min-width: 250px;
}

@keyframes slideInRight {
    from {
        opacity: 0;
        transform: translateX(100px);
    }
    to {
        opacity: 1;
        transform: translateX(0);
    }
}

.toast.success {
    border-left: 3px solid #10b981;
}

.toast.error {
    border-left: 3px solid #ef4444;
}

.toast-icon {
    width: 20px;
    height: 20px;
}

.toast-icon.success {
    color: #10b981;
}

.toast-icon.error {
    color: #ef4444;
}

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

::-webkit-scrollbar-track {
    background: transparent;
}

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

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

/* ===== RESPONSIVE ===== */
@media (max-width: 1024px) {
    .writeup-layout {
        grid-template-columns: 1fr;
        gap: 2rem;
    }
    
    .sidebar {
        position: static;
        max-height: none;
        background: var(--glass-bg);
        border: 1px solid var(--border-color);
        border-radius: 12px;
        padding: 1.5rem;
    }
}

@media (max-width: 768px) {
    .container {
        padding: 1rem;
    }
    
    .nav-container {
        padding: 1rem;
    }
    
    .home-header h1 {
        font-size: 2rem;
    }
    
    .writeups-grid {
        grid-template-columns: 1fr;
    }
    
    .content-header h1 {
        font-size: 2rem;
    }
    
    .markdown-content {
        font-size: 1rem;
    }
    
    #toast-container {
        right: 1rem;
        left: 1rem;
    }
    
    .toast {
        min-width: auto;
    }
}

@media (max-width: 480px) {
    .home-header h1 {
        font-size: 1.75rem;
    }
    
    .content-header h1 {
        font-size: 1.75rem;
    }
    
    .filter-chips {
        flex-direction: column;
        align-items: stretch;
    }
    
    .chip {
        text-align: center;
    }
}