/* ==========================================================================
   AMAN.LEARN - Modern Documentation Design System
   Self-hosted fonts, engineering graph-paper grid, refined dark/light themes.
   ========================================================================== */

/* --------------------------------------------------------------------------
   Self-Hosted Font Faces
   -------------------------------------------------------------------------- */
@font-face {
    font-family: 'Inter';
    font-style: normal;
    font-weight: 100 900;
    font-display: swap;
    src: url('../fonts/inter-var-latin.woff2') format('woff2');
    unicode-range: U+0000-00FF, U+0131, U+0152-0153, U+02BB-02BC, U+02C6, U+02DA, U+02DC, U+0304, U+0308, U+0329, U+2000-206F, U+2074, U+20AC, U+2122, U+2191, U+2193, U+2212, U+2215, U+FEFF, U+FFFD;
}

@font-face {
    font-family: 'JetBrains Mono';
    font-style: normal;
    font-weight: 100 800;
    font-display: swap;
    src: url('../fonts/jetbrains-mono-var-latin.woff2') format('woff2');
    unicode-range: U+0000-00FF, U+0131, U+0152-0153, U+02BB-02BC, U+02C6, U+02DA, U+02DC, U+0304, U+0308, U+0329, U+2000-206F, U+2074, U+20AC, U+2122, U+2191, U+2193, U+2212, U+2215, U+FEFF, U+FFFD;
}

/* --------------------------------------------------------------------------
   Design Tokens - Dark Mode (Default)
   -------------------------------------------------------------------------- */
:root {
    --bg-primary: #0a0e17;
    --bg-secondary: #111726;
    --bg-tertiary: #182238;
    --bg-card: rgba(17, 23, 38, 0.85);
    --bg-card-hover: rgba(24, 34, 56, 0.92);
    --bg-glass: rgba(10, 14, 23, 0.85);
    --bg-input: #121929;

    --border-subtle: #1e293b;
    --border-accent: #334155;
    --border-glow: rgba(56, 189, 248, 0.25);

    --text-primary: #f8fafc;
    --text-secondary: #94a3b8;
    --text-muted: #64748b;
    --text-inverse: #0a0e17;

    --accent: #38bdf8;
    --accent-light: #7dd3fc;
    --accent-dark: #0284c7;
    --accent-gradient: linear-gradient(135deg, #38bdf8 0%, #6366f1 50%, #a855f7 100%);
    --card-glow: 0 0 35px -10px rgba(56, 189, 248, 0.15);

    /* Graph-Paper Grid Background Tokens */
    --grid-subtle: rgba(56, 189, 248, 0.035);
    --grid-major: rgba(56, 189, 248, 0.08);
    --glow-accent: rgba(56, 189, 248, 0.07);

    /* Interview Heat Colors */
    --heat-low: #38bdf8;
    --heat-medium: #fbbf24;
    --heat-high: #f97316;
    --heat-vhigh: #ef4444;

    /* Fonts & Radii */
    --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    --font-mono: 'JetBrains Mono', 'Fira Code', Menlo, Consolas, monospace;

    --radius-sm: 6px;
    --radius-md: 10px;
    --radius-lg: 16px;
    --radius-xl: 24px;
    --radius-full: 9999px;

    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.25);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.35), 0 2px 4px -2px rgba(0, 0, 0, 0.3);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.45), 0 4px 6px -4px rgba(0, 0, 0, 0.4);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.55), 0 8px 10px -6px rgba(0, 0, 0, 0.5);

    --transition-fast: 150ms cubic-bezier(0.4, 0, 0.2, 1);
    --transition-base: 250ms cubic-bezier(0.4, 0, 0.2, 1);
    --transition-slow: 350ms cubic-bezier(0.4, 0, 0.2, 1);

    --max-width: 1280px;
    --nav-height: 64px;
}

/* Light Theme Variables */
[data-theme="light"] {
    --bg-primary: #f8fafc;
    --bg-secondary: #ffffff;
    --bg-tertiary: #f1f5f9;
    --bg-card: rgba(255, 255, 255, 0.92);
    --bg-card-hover: #ffffff;
    --bg-glass: rgba(248, 250, 252, 0.88);
    --bg-input: #f1f5f9;

    --border-subtle: #e2e8f0;
    --border-accent: #cbd5e1;
    --border-glow: rgba(2, 132, 199, 0.2);

    --text-primary: #0f172a;
    --text-secondary: #475569;
    --text-muted: #94a3b8;
    --text-inverse: #ffffff;

    --accent: #0284c7;
    --accent-light: #0ea5e9;
    --accent-dark: #0369a1;
    --accent-gradient: linear-gradient(135deg, #0284c7 0%, #4f46e5 50%, #9333ea 100%);
    --card-glow: 0 10px 25px -5px rgba(2, 132, 199, 0.08);

    --grid-subtle: rgba(2, 132, 199, 0.04);
    --grid-major: rgba(2, 132, 199, 0.09);
    --glow-accent: rgba(2, 132, 199, 0.05);

    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.07), 0 2px 4px -2px rgba(0, 0, 0, 0.05);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.08), 0 4px 6px -4px rgba(0, 0, 0, 0.04);
}

/* --------------------------------------------------------------------------
   Base Reset & Graph-Paper Grid Background
   -------------------------------------------------------------------------- */
*, *::before, *::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

html {
    font-family: var(--font-sans);
    background-color: var(--bg-primary);
    color: var(--text-primary);
    line-height: 1.6;
    scroll-behavior: smooth;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

body {
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    overflow-x: hidden;
    background-color: var(--bg-primary);
    background-image:
        linear-gradient(var(--grid-subtle) 1px, transparent 1px),
        linear-gradient(90deg, var(--grid-subtle) 1px, transparent 1px),
        linear-gradient(var(--grid-major) 1px, transparent 1px),
        linear-gradient(90deg, var(--grid-major) 1px, transparent 1px),
        radial-gradient(circle at 50% 0%, var(--glow-accent) 0%, transparent 70%);
    background-size: 24px 24px, 24px 24px, 120px 120px, 120px 120px, 100% 100%;
    background-position: 0 0, 0 0, 0 0, 0 0, center top;
    background-attachment: fixed;
}

a {
    color: inherit;
    text-decoration: none;
}

button {
    font-family: inherit;
    cursor: pointer;
    border: none;
    background: none;
}

/* Reading Progress Bar */
#reading-progress {
    position: fixed;
    top: 0;
    left: 0;
    width: 0%;
    height: 3px;
    background: var(--accent-gradient);
    z-index: 1000;
    transition: width 100ms ease-out;
}

/* --------------------------------------------------------------------------
   Navbar
   -------------------------------------------------------------------------- */
.navbar {
    position: sticky;
    top: 0;
    height: var(--nav-height);
    background: var(--bg-glass);
    backdrop-filter: blur(14px);
    -webkit-backdrop-filter: blur(14px);
    border-bottom: 1px solid var(--border-subtle);
    z-index: 100;
    display: flex;
    align-items: center;
}

.navbar-inner {
    width: 100%;
    max-width: var(--max-width);
    margin: 0 auto;
    padding: 0 1.5rem;
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.navbar-brand {
    display: inline-flex;
    align-items: center;
    font-size: 1.25rem;
    font-weight: 800;
    color: var(--text-primary);
    transition: opacity var(--transition-fast);
}

.navbar-brand:hover {
    opacity: 0.85;
}

.brand-text {
    font-weight: 800;
    letter-spacing: -0.02em;
    font-size: 1.25rem;
    color: var(--text-primary);
}

.theme-accent-text {
    color: var(--accent);
    font-weight: 800;
}

.navbar-actions {
    display: flex;
    align-items: center;
    gap: 0.65rem;
}

.nav-link {
    display: inline-flex;
    align-items: center;
    gap: 0.45rem;
    font-size: 0.85rem;
    font-weight: 600;
    color: var(--text-secondary);
    padding: 0.45rem 0.85rem;
    border-radius: var(--radius-md);
    background: var(--bg-secondary);
    border: 1px solid var(--border-subtle);
    transition: all var(--transition-fast);
}

.nav-link:hover {
    color: var(--text-primary);
    border-color: var(--border-accent);
    background: var(--bg-tertiary);
    transform: translateY(-1px);
}

.nav-link.portfolio-link {
    color: var(--accent);
    border-color: rgba(56, 189, 248, 0.25);
}

.nav-link.portfolio-link:hover {
    background: rgba(56, 189, 248, 0.1);
    border-color: var(--accent);
}

.nav-search-btn {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    font-size: 0.85rem;
    color: var(--text-muted);
    padding: 0.45rem 0.85rem;
    border-radius: var(--radius-md);
    background: var(--bg-secondary);
    border: 1px solid var(--border-subtle);
    transition: all var(--transition-fast);
}

.nav-search-btn:hover {
    color: var(--text-primary);
    border-color: var(--border-accent);
    background: var(--bg-tertiary);
}

.nav-search-btn kbd {
    font-family: var(--font-mono);
    font-size: 0.72rem;
    padding: 0.15rem 0.35rem;
    border-radius: var(--radius-sm);
    background: var(--bg-tertiary);
    border: 1px solid var(--border-subtle);
    color: var(--text-secondary);
}

.icon-btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 38px;
    height: 38px;
    border-radius: var(--radius-md);
    background: var(--bg-secondary);
    color: var(--text-secondary);
    border: 1px solid var(--border-subtle);
    transition: all var(--transition-fast);
}

.icon-btn:hover {
    color: var(--text-primary);
    border-color: var(--border-accent);
    background: var(--bg-tertiary);
    transform: translateY(-1px);
}

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

/* --------------------------------------------------------------------------
   Main App Container
   -------------------------------------------------------------------------- */
#app {
    flex: 1;
    width: 100%;
    max-width: var(--max-width);
    margin: 0 auto;
    padding: 2rem 1.5rem 4rem;
}

.view-container {
    animation: fadeIn var(--transition-base);
}

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(6px); }
    to { opacity: 1; transform: translateY(0); }
}

/* --------------------------------------------------------------------------
   Landing Page / Hero Section
   -------------------------------------------------------------------------- */
.hero-section {
    text-align: center;
    padding: 3.5rem 1rem 2.5rem;
    max-width: 860px;
    margin: 0 auto 3rem;
}

.hero-pill {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.35rem 0.9rem;
    border-radius: var(--radius-full);
    background: var(--bg-secondary);
    border: 1px solid var(--border-subtle);
    font-size: 0.8rem;
    font-weight: 600;
    color: var(--text-secondary);
    margin-bottom: 1.5rem;
}

.hero-title {
    font-size: 2.75rem;
    font-weight: 800;
    line-height: 1.18;
    letter-spacing: -0.03em;
    margin-bottom: 1.25rem;
}

.gradient-text {
    background: var(--accent-gradient);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
}

.hero-subtitle {
    font-size: 1.15rem;
    color: var(--text-secondary);
    line-height: 1.6;
    margin-bottom: 2rem;
    font-weight: 400;
}

/* Big Responsive Hero Search Bar */
.hero-search-container {
    width: 100%;
    max-width: 680px;
    margin: 1.75rem auto 0;
    padding: 0 0.5rem;
}

.hero-search-bar {
    width: 100%;
    display: flex;
    align-items: center;
    gap: 0.85rem;
    padding: 0.85rem 1.35rem;
    background: var(--bg-card);
    border: 1.5px solid var(--border-subtle);
    border-radius: var(--radius-full);
    cursor: pointer;
    box-shadow: 0 4px 20px rgba(0, 0, 0, 0.15);
    transition: all var(--transition-base);
    user-select: none;
}

.hero-search-bar:hover,
.hero-search-bar:focus-visible {
    border-color: var(--accent);
    background: var(--bg-card-hover);
    box-shadow: 0 6px 24px rgba(56, 189, 248, 0.22);
    transform: translateY(-2px);
    outline: none;
}

.hero-search-icon {
    color: var(--accent);
    flex-shrink: 0;
    transition: transform var(--transition-fast);
}

.hero-search-bar:hover .hero-search-icon {
    transform: scale(1.1);
}

.hero-search-text {
    flex: 1;
    text-align: left;
    color: var(--text-muted);
    font-size: 0.95rem;
    font-weight: 400;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

.hero-search-bar:hover .hero-search-text {
    color: var(--text-secondary);
}

.hero-search-shortcut {
    display: flex;
    align-items: center;
    gap: 0.25rem;
    flex-shrink: 0;
}

.hero-search-shortcut kbd {
    font-family: var(--font-mono);
    font-size: 0.75rem;
    font-weight: 600;
    padding: 0.2rem 0.55rem;
    border-radius: var(--radius-sm);
    background: var(--bg-secondary);
    border: 1px solid var(--border-subtle);
    color: var(--text-secondary);
}

.subjects-header {
    margin-bottom: 1.75rem;
    display: flex;
    flex-direction: column;
    gap: 0.25rem;
}

.subjects-section-title {
    font-size: 1.5rem;
    font-weight: 800;
    letter-spacing: -0.02em;
}

.subjects-section-desc {
    color: var(--text-muted);
    font-size: 0.92rem;
}

/* --------------------------------------------------------------------------
   Subject Cards Grid
   -------------------------------------------------------------------------- */
.subjects-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(350px, 1fr));
    gap: 1.5rem;
}

.subject-card {
    background: var(--bg-card);
    border: 1px solid var(--border-subtle);
    border-radius: var(--radius-lg);
    padding: 1.75rem;
    display: flex;
    flex-direction: column;
    transition: all var(--transition-base);
    position: relative;
    overflow: hidden;
    backdrop-filter: blur(8px);
}

.subject-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 3px;
    background: var(--card-accent, var(--accent));
    opacity: 0.8;
}

.subject-card.active {
    cursor: pointer;
}

.subject-card.active:hover {
    border-color: var(--card-accent, var(--accent));
    transform: translateY(-3px);
    box-shadow: 0 10px 25px -5px rgba(0, 0, 0, 0.4), var(--card-glow);
}

.subject-card.disabled {
    opacity: 0.65;
    cursor: default;
}

.subject-card-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin-bottom: 1rem;
}

.subject-icon-box {
    font-size: 1.75rem;
    background: var(--bg-secondary);
    border: 1px solid var(--border-subtle);
    width: 48px;
    height: 48px;
    border-radius: var(--radius-md);
    display: flex;
    align-items: center;
    justify-content: center;
}

.subject-badge {
    font-size: 0.72rem;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    padding: 0.25rem 0.65rem;
    border-radius: var(--radius-full);
}

.subject-badge.active {
    background: rgba(16, 185, 129, 0.15);
    color: #10b981;
    border: 1px solid rgba(16, 185, 129, 0.3);
}

.subject-badge.planned {
    background: rgba(100, 116, 139, 0.15);
    color: var(--text-muted);
    border: 1px solid rgba(100, 116, 139, 0.25);
}

.subject-title {
    font-size: 1.35rem;
    font-weight: 700;
    letter-spacing: -0.01em;
    margin-bottom: 0.35rem;
}

.subject-tagline {
    font-size: 0.88rem;
    font-weight: 500;
    color: var(--text-secondary);
    margin-bottom: 0.75rem;
    line-height: 1.45;
}

.subject-desc {
    font-size: 0.85rem;
    color: var(--text-muted);
    line-height: 1.55;
    margin-bottom: 1.5rem;
    flex-grow: 1;
}

.subject-card-footer {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding-top: 1rem;
    border-top: 1px solid var(--border-subtle);
    font-size: 0.82rem;
}

.subject-stats {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    color: var(--text-muted);
    font-weight: 500;
}

.subject-action-btn {
    display: inline-flex;
    align-items: center;
    gap: 0.45rem;
    font-weight: 600;
    color: var(--card-accent, var(--accent));
    transition: gap var(--transition-fast);
}

.subject-card.active:hover .subject-action-btn {
    gap: 0.65rem;
}

/* --------------------------------------------------------------------------
   Subject Table of Contents (TOC) View
   -------------------------------------------------------------------------- */
.breadcrumb {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-size: 0.85rem;
    color: var(--text-muted);
    margin-bottom: 1.5rem;
    flex-wrap: wrap;
}

.breadcrumb a {
    color: var(--text-secondary);
    transition: color var(--transition-fast);
}

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

.breadcrumb .sep {
    color: var(--border-accent);
}

.breadcrumb .current {
    color: var(--text-primary);
    font-weight: 500;
}

.subject-hero {
    background: var(--bg-card);
    border: 1px solid var(--border-subtle);
    border-radius: var(--radius-lg);
    padding: 2rem;
    margin-bottom: 2rem;
    backdrop-filter: blur(8px);
    position: relative;
    overflow: hidden;
}

.subject-hero::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 4px;
    background: var(--accent-gradient);
}

.subject-hero-top {
    display: flex;
    align-items: flex-start;
    gap: 1.25rem;
    margin-bottom: 1.25rem;
}

.subject-hero-icon {
    font-size: 2.25rem;
    background: var(--bg-secondary);
    border: 1px solid var(--border-subtle);
    width: 60px;
    height: 60px;
    border-radius: var(--radius-md);
    display: flex;
    align-items: center;
    justify-content: center;
    flex-shrink: 0;
}

.subject-hero-title {
    font-size: 1.85rem;
    font-weight: 800;
    letter-spacing: -0.02em;
    margin-bottom: 0.25rem;
}

.subject-hero-subtitle {
    color: var(--text-secondary);
    font-size: 0.95rem;
    line-height: 1.5;
}

.stats-bar {
    display: flex;
    flex-wrap: wrap;
    gap: 1rem;
    padding-top: 1.25rem;
    border-top: 1px solid var(--border-subtle);
}

.stat-pill {
    background: var(--bg-secondary);
    border: 1px solid var(--border-subtle);
    padding: 0.5rem 0.9rem;
    border-radius: var(--radius-md);
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-size: 0.85rem;
}

.stat-pill .num {
    font-weight: 700;
    color: var(--text-primary);
}

.stat-pill .label {
    color: var(--text-muted);
}

/* TOC Search & Filter */
.toc-controls {
    display: flex;
    gap: 1rem;
    margin-bottom: 2rem;
    flex-wrap: wrap;
}

.search-box {
    flex: 1;
    min-width: 260px;
    position: relative;
}

.search-input {
    width: 100%;
    background: var(--bg-input);
    border: 1px solid var(--border-subtle);
    border-radius: var(--radius-md);
    padding: 0.75rem 1rem 0.75rem 2.6rem;
    color: var(--text-primary);
    font-size: 0.9rem;
    outline: none;
    transition: all var(--transition-fast);
}

.search-input:focus {
    border-color: var(--accent);
    box-shadow: 0 0 0 3px rgba(56, 189, 248, 0.15);
}

.search-icon {
    position: absolute;
    left: 0.9rem;
    top: 50%;
    transform: translateY(-50%);
    color: var(--text-muted);
    pointer-events: none;
}

/* Phase Sections */
.phase-group {
    margin-bottom: 2.5rem;
    scroll-margin-top: 80px;
}

.phase-header {
    display: flex;
    align-items: center;
    gap: 0.85rem;
    margin-bottom: 0.6rem;
}

.phase-badge {
    font-size: 0.75rem;
    font-weight: 700;
    letter-spacing: 0.05em;
    text-transform: uppercase;
    background: rgba(56, 189, 248, 0.15);
    color: var(--accent);
    border: 1px solid rgba(56, 189, 248, 0.3);
    padding: 0.2rem 0.6rem;
    border-radius: var(--radius-sm);
}

.phase-title {
    font-size: 1.35rem;
    font-weight: 700;
    letter-spacing: -0.01em;
}

.phase-quote {
    color: var(--text-muted);
    font-style: italic;
    font-size: 0.9rem;
    margin-bottom: 1rem;
    padding-left: 0.75rem;
    border-left: 2px solid var(--border-accent);
}

/* Responsive Table */
.table-responsive {
    width: 100%;
    overflow-x: auto;
    background: var(--bg-card);
    border: 1px solid var(--border-subtle);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-sm);
}

.toc-table {
    width: 100%;
    border-collapse: collapse;
    font-size: 0.9rem;
    text-align: left;
}

.toc-table th {
    background: var(--bg-secondary);
    color: var(--text-muted);
    font-size: 0.78rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    padding: 0.85rem 1rem;
    border-bottom: 1px solid var(--border-subtle);
    white-space: nowrap;
}

.toc-table td {
    padding: 0.9rem 1rem;
    border-bottom: 1px solid var(--border-subtle);
    color: var(--text-secondary);
    vertical-align: middle;
}

.toc-table tr:last-child td {
    border-bottom: none;
}

.toc-table tbody tr {
    transition: background var(--transition-fast);
}

.toc-table tbody tr:hover {
    background: var(--bg-tertiary);
}

.topic-nn {
    font-family: var(--font-mono);
    font-weight: 600;
    font-size: 0.82rem;
    color: var(--accent);
}

.topic-title-link {
    font-weight: 600;
    color: var(--text-primary);
    display: inline-flex;
    align-items: center;
    gap: 0.4rem;
    transition: color var(--transition-fast);
}

.topic-title-link:hover {
    color: var(--accent);
    text-decoration: underline;
}

.topic-planned-title {
    color: var(--text-muted);
    font-style: italic;
}

.heat-badge {
    display: inline-flex;
    align-items: center;
    gap: 0.3rem;
    font-size: 0.75rem;
    font-weight: 600;
    padding: 2px 8px;
    border-radius: var(--radius-full);
    white-space: nowrap;
}

.heat-vhigh {
    background: rgba(239, 68, 68, 0.15);
    color: var(--heat-vhigh);
    border: 1px solid rgba(239, 68, 68, 0.3);
}

.heat-high {
    background: rgba(249, 115, 22, 0.15);
    color: var(--heat-high);
    border: 1px solid rgba(249, 115, 22, 0.3);
}

.heat-medium {
    background: rgba(251, 191, 36, 0.15);
    color: var(--heat-medium);
    border: 1px solid rgba(251, 191, 36, 0.3);
}

.heat-low {
    background: rgba(56, 189, 248, 0.15);
    color: var(--heat-low);
    border: 1px solid rgba(56, 189, 248, 0.3);
}

.key-concepts-cell {
    font-size: 0.85rem;
    color: var(--text-muted);
    max-width: 480px;
    line-height: 1.45;
}

/* Topic Completion Checkbox in Table */
.toc-check-btn {
    cursor: pointer;
    background: transparent;
    border: none;
    padding: 0;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    color: var(--text-muted);
    transition: all var(--transition-fast);
}

.toc-check-btn.checked {
    color: #10b981;
}

.toc-check-btn:hover {
    transform: scale(1.15);
}

/* --------------------------------------------------------------------------
   Note View (Document Reader)
   -------------------------------------------------------------------------- */
.note-container {
    display: grid;
    grid-template-columns: minmax(0, 1fr) 260px;
    gap: 2.5rem;
    align-items: start;
    position: relative;
}

.note-content-column {
    min-width: 0;
}

.note-header-card {
    background: var(--bg-card);
    border: 1px solid var(--border-subtle);
    border-radius: var(--radius-lg);
    padding: 1.5rem 1.75rem;
    margin-bottom: 2rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
    gap: 1rem;
}

.note-meta-badges {
    display: flex;
    align-items: center;
    gap: 0.65rem;
    flex-wrap: wrap;
    margin-top: 0.35rem;
}

.read-time-badge, .edit-gh-badge, .mark-done-btn {
    display: inline-flex;
    align-items: center;
    gap: 0.35rem;
    font-size: 0.78rem;
    font-weight: 600;
    padding: 0.25rem 0.65rem;
    border-radius: var(--radius-full);
    background: var(--bg-secondary);
    border: 1px solid var(--border-subtle);
    color: var(--text-secondary);
    transition: all var(--transition-fast);
}

.edit-gh-badge:hover {
    color: var(--text-primary);
    border-color: var(--border-accent);
    background: var(--bg-tertiary);
}

.mark-done-btn {
    cursor: pointer;
}

.mark-done-btn.completed {
    background: rgba(16, 185, 129, 0.15);
    color: #10b981;
    border-color: rgba(16, 185, 129, 0.4);
}

.mark-done-btn:hover {
    transform: translateY(-1px);
}

.back-btn {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    font-size: 0.85rem;
    font-weight: 600;
    color: var(--text-secondary);
    padding: 0.5rem 1rem;
    border-radius: var(--radius-md);
    background: var(--bg-secondary);
    border: 1px solid var(--border-subtle);
    transition: all var(--transition-fast);
}

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

/* Markdown Render Output */
.markdown-body {
    background: var(--bg-card);
    border: 1px solid var(--border-subtle);
    border-radius: var(--radius-lg);
    padding: 2.5rem;
    color: var(--text-primary);
    font-size: 1rem;
    line-height: 1.75;
    box-shadow: var(--shadow-sm);
}

.markdown-body h1 {
    font-size: 2.2rem;
    font-weight: 800;
    letter-spacing: -0.03em;
    margin-bottom: 1.5rem;
    padding-bottom: 0.75rem;
    border-bottom: 1px solid var(--border-subtle);
    line-height: 1.25;
}

.markdown-body h2 {
    font-size: 1.6rem;
    font-weight: 700;
    letter-spacing: -0.02em;
    margin-top: 2.5rem;
    margin-bottom: 1rem;
    padding-bottom: 0.5rem;
    border-bottom: 1px solid var(--border-subtle);
    scroll-margin-top: 80px;
}

.markdown-body h3 {
    font-size: 1.25rem;
    font-weight: 600;
    margin-top: 2rem;
    margin-bottom: 0.75rem;
    scroll-margin-top: 80px;
}

.markdown-body h4 {
    font-size: 1.05rem;
    font-weight: 600;
    margin-top: 1.5rem;
    margin-bottom: 0.5rem;
}

.markdown-body p {
    margin-bottom: 1.25rem;
    color: var(--text-secondary);
}

.markdown-body ul, .markdown-body ol {
    margin-bottom: 1.25rem;
    padding-left: 1.75rem;
    color: var(--text-secondary);
}

.markdown-body li {
    margin-bottom: 0.4rem;
}

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

.markdown-body a {
    color: var(--accent);
    text-decoration: underline;
    text-underline-offset: 3px;
    font-weight: 500;
}

.markdown-body a:hover {
    color: var(--accent-light);
}

/* Inline Code & Code Blocks */
.markdown-body code {
    font-family: var(--font-mono);
    font-size: 0.88em;
    padding: 0.2em 0.4em;
    border-radius: var(--radius-sm);
    background: var(--bg-secondary);
    border: 1px solid var(--border-subtle);
    color: var(--accent);
}

.code-block-wrapper {
    position: relative;
    margin: 1.5rem 0;
    border-radius: var(--radius-md);
    overflow: hidden;
    border: 1px solid var(--border-subtle);
    background: #0d1117;
}

[data-theme="light"] .code-block-wrapper {
    background: #f6f8fa;
}

.code-block-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 0.5rem 1rem;
    background: #161b22;
    border-bottom: 1px solid #21262d;
    font-family: var(--font-mono);
    font-size: 0.75rem;
    color: #8b949e;
}

[data-theme="light"] .code-block-header {
    background: #eaeef2;
    border-bottom: 1px solid #d0d7de;
    color: #57606a;
}

.copy-code-btn {
    display: inline-flex;
    align-items: center;
    gap: 0.35rem;
    font-size: 0.75rem;
    color: #8b949e;
    padding: 0.25rem 0.6rem;
    border-radius: var(--radius-sm);
    background: rgba(255, 255, 255, 0.05);
    border: 1px solid rgba(255, 255, 255, 0.1);
    transition: all var(--transition-fast);
}

.copy-code-btn:hover {
    color: #f0f6fc;
    background: rgba(255, 255, 255, 0.15);
}

[data-theme="light"] .copy-code-btn {
    color: #57606a;
    background: rgba(0, 0, 0, 0.04);
    border: 1px solid rgba(0, 0, 0, 0.1);
}

[data-theme="light"] .copy-code-btn:hover {
    color: #24292f;
    background: rgba(0, 0, 0, 0.08);
}

.code-block-wrapper pre {
    margin: 0 !important;
    padding: 1.25rem !important;
    overflow-x: auto;
    background: transparent !important;
}

.code-block-wrapper pre code {
    background: transparent !important;
    border: none !important;
    padding: 0 !important;
    font-size: 0.88rem !important;
    line-height: 1.5 !important;
}

/* Markdown Tables */
.markdown-body table {
    width: 100%;
    border-collapse: collapse;
    margin: 1.5rem 0;
    font-size: 0.92rem;
    overflow-x: auto;
    display: block;
}

.markdown-body th {
    background: var(--bg-secondary);
    font-weight: 600;
    color: var(--text-primary);
    padding: 0.75rem 1rem;
    border: 1px solid var(--border-subtle);
    text-align: left;
}

.markdown-body td {
    padding: 0.75rem 1rem;
    border: 1px solid var(--border-subtle);
    color: var(--text-secondary);
}

.markdown-body tr:nth-child(even) td {
    background: rgba(255, 255, 255, 0.015);
}

/* Note Images */
.note-image-wrapper {
    margin: 2rem 0;
    text-align: center;
}

.note-image-wrapper img {
    max-width: 100%;
    height: auto;
    border-radius: var(--radius-md);
    border: 1px solid var(--border-subtle);
    box-shadow: var(--shadow-md);
}

.image-caption {
    display: block;
    font-size: 0.82rem;
    color: var(--text-muted);
    margin-top: 0.5rem;
    font-style: italic;
}

/* PlantUML Diagram Source Details */
details.diagram-source {
    margin: 1.5rem 0;
    border: 1px solid var(--border-subtle);
    border-radius: var(--radius-md);
    background: var(--bg-secondary);
    overflow: hidden;
    transition: border-color var(--transition-fast);
}

details.diagram-source summary {
    padding: 0.75rem 1rem;
    font-size: 0.88rem;
    font-weight: 600;
    color: var(--text-primary);
    cursor: pointer;
    user-select: none;
    background: var(--bg-tertiary);
    display: flex;
    align-items: center;
    gap: 0.5rem;
    transition: color var(--transition-fast);
}

details.diagram-source summary:hover {
    color: var(--accent);
}

details.diagram-source pre.plantuml-code {
    padding: 1rem 1.25rem;
    margin: 0;
    font-family: var(--font-mono);
    font-size: 0.82rem;
    line-height: 1.5;
    overflow-x: auto;
    background: var(--bg-input);
    color: var(--text-secondary);
    border-top: 1px solid var(--border-subtle);
}

/* GitHub Style Alerts / Callouts */
.callout {
    margin: 1.5rem 0;
    padding: 1rem 1.25rem;
    border-radius: var(--radius-md);
    border-left: 4px solid;
    background: var(--bg-secondary);
}

.callout-header {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-weight: 700;
    font-size: 0.9rem;
    margin-bottom: 0.5rem;
    text-transform: uppercase;
    letter-spacing: 0.03em;
}

.callout-content {
    font-size: 0.95rem;
    line-height: 1.6;
    color: var(--text-secondary);
}

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

.callout-note {
    border-left-color: #3b82f6;
    background: rgba(59, 130, 246, 0.08);
}
.callout-note .callout-header { color: #60a5fa; }

.callout-tip {
    border-left-color: #10b981;
    background: rgba(16, 185, 129, 0.08);
}
.callout-tip .callout-header { color: #34d399; }

.callout-important {
    border-left-color: #a855f7;
    background: rgba(168, 85, 247, 0.08);
}
.callout-important .callout-header { color: #c084fc; }

.callout-warning {
    border-left-color: #f59e0b;
    background: rgba(245, 158, 11, 0.08);
}
.callout-warning .callout-header { color: #fbbf24; }

.callout-caution {
    border-left-color: #ef4444;
    background: rgba(239, 68, 68, 0.08);
}
.callout-caution .callout-header { color: #f87171; }

/* Sticky On-This-Page TOC Sidebar */
.note-sidebar {
    position: sticky;
    top: calc(var(--nav-height) + 1.5rem);
    background: var(--bg-card);
    border: 1px solid var(--border-subtle);
    border-radius: var(--radius-lg);
    padding: 1.25rem;
    max-height: calc(100vh - var(--nav-height) - 3rem);
    overflow-y: auto;
    font-size: 0.85rem;
}

.sidebar-title {
    font-size: 0.8rem;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    color: var(--text-muted);
    margin-bottom: 0.85rem;
}

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

.sidebar-toc-item {
    margin-bottom: 0.35rem;
}

.sidebar-toc-item a {
    color: var(--text-muted);
    display: block;
    padding: 0.3rem 0.6rem;
    border-radius: var(--radius-sm);
    transition: all var(--transition-fast);
    line-height: 1.4;
    border-left: 2px solid transparent;
}

.sidebar-toc-item a:hover {
    color: var(--text-primary);
    background: var(--bg-secondary);
}

.sidebar-toc-item.active a {
    color: var(--accent);
    background: var(--bg-secondary);
    font-weight: 600;
    border-left-color: var(--accent);
}

.sidebar-toc-item.level-3 {
    padding-left: 0.75rem;
    font-size: 0.8rem;
}

/* Note Pagination (Prev / Next) */
.note-pagination {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 1.25rem;
    margin-top: 2rem;
}

.pagination-card {
    background: var(--bg-card);
    border: 1px solid var(--border-subtle);
    border-radius: var(--radius-lg);
    padding: 1.25rem 1.5rem;
    display: flex;
    flex-direction: column;
    transition: all var(--transition-base);
}

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

.pagination-card.next {
    text-align: right;
    align-items: flex-end;
}

.pagination-sub {
    font-size: 0.75rem;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    color: var(--text-muted);
    font-weight: 600;
    margin-bottom: 0.25rem;
}

.pagination-title {
    font-size: 0.95rem;
    font-weight: 600;
    color: var(--text-primary);
}

/* Coming Soon & State Boxes */
.state-box {
    text-align: center;
    padding: 4rem 1.5rem;
    background: var(--bg-card);
    border: 1px solid var(--border-subtle);
    border-radius: var(--radius-lg);
    max-width: 600px;
    margin: 2rem auto;
}

.state-icon {
    font-size: 3rem;
    margin-bottom: 1rem;
}

.state-badge {
    display: inline-block;
    font-size: 0.75rem;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    padding: 0.25rem 0.75rem;
    border-radius: var(--radius-full);
    background: rgba(56, 189, 248, 0.15);
    color: var(--accent);
    border: 1px solid rgba(56, 189, 248, 0.3);
    margin-bottom: 1rem;
}

.spinner {
    width: 40px;
    height: 40px;
    border: 3px solid var(--border-subtle);
    border-top-color: var(--accent);
    border-radius: 50%;
    animation: spin 0.8s linear infinite;
    margin: 0 auto 1.25rem;
}

@keyframes spin {
    to { transform: rotate(360deg); }
}

/* --------------------------------------------------------------------------
   Search Modal
   -------------------------------------------------------------------------- */
.search-modal-backdrop {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(0, 0, 0, 0.7);
    backdrop-filter: blur(6px);
    -webkit-backdrop-filter: blur(6px);
    z-index: 200;
    display: none;
    align-items: flex-start;
    justify-content: center;
    padding: 10vh 1.5rem 2rem;
    animation: fadeInModal 150ms ease-out;
}

.search-modal-backdrop.open {
    display: flex;
}

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

.search-modal-card {
    background: var(--bg-secondary);
    border: 1px solid var(--border-accent);
    border-radius: var(--radius-lg);
    width: 100%;
    max-width: 640px;
    box-shadow: var(--shadow-xl);
    overflow: hidden;
    display: flex;
    flex-direction: column;
    max-height: 70vh;
}

.search-modal-header {
    display: flex;
    align-items: center;
    padding: 0.85rem 1.25rem;
    border-bottom: 1px solid var(--border-subtle);
    gap: 0.75rem;
}

.search-modal-input {
    flex: 1;
    background: transparent;
    border: none;
    font-size: 1.05rem;
    color: var(--text-primary);
    outline: none;
}

.search-modal-close {
    color: var(--text-muted);
    font-size: 1.25rem;
    padding: 0.2rem 0.5rem;
    border-radius: var(--radius-sm);
    transition: color var(--transition-fast);
}

.search-modal-close:hover {
    color: var(--text-primary);
}

.search-results-list {
    overflow-y: auto;
    padding: 0.5rem;
    list-style: none;
}

.search-result-item {
    padding: 0.75rem 1rem;
    border-radius: var(--radius-md);
    cursor: pointer;
    transition: background var(--transition-fast);
    display: flex;
    flex-direction: column;
    gap: 0.25rem;
}

.search-result-item:hover, .search-result-item.selected {
    background: var(--bg-tertiary);
}

.search-result-top {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 0.5rem;
}

.search-result-pillar {
    font-size: 0.72rem;
    font-weight: 700;
    text-transform: uppercase;
    color: var(--accent);
}

.search-result-title {
    font-size: 0.95rem;
    font-weight: 600;
    color: var(--text-primary);
}

.search-result-concepts {
    font-size: 0.8rem;
    color: var(--text-muted);
    line-height: 1.4;
}

.search-modal-footer {
    padding: 0.65rem 1.25rem;
    border-top: 1px solid var(--border-subtle);
    display: flex;
    align-items: center;
    justify-content: space-between;
    font-size: 0.75rem;
    color: var(--text-muted);
    background: var(--bg-primary);
}

.search-hints {
    display: flex;
    gap: 0.85rem;
}

/* --------------------------------------------------------------------------
   Back to Top Floating Button
   -------------------------------------------------------------------------- */
.back-to-top-btn {
    position: fixed;
    bottom: 2rem;
    right: 2rem;
    width: 44px;
    height: 44px;
    border-radius: 50%;
    background: var(--bg-secondary);
    border: 1px solid var(--border-accent);
    color: var(--text-primary);
    box-shadow: var(--shadow-lg);
    display: flex;
    align-items: center;
    justify-content: center;
    opacity: 0;
    visibility: hidden;
    transform: translateY(12px);
    transition: all var(--transition-base);
    z-index: 90;
}

.back-to-top-btn.visible {
    opacity: 1;
    visibility: visible;
    transform: translateY(0);
}

.back-to-top-btn:hover {
    background: var(--accent);
    color: #fff;
    border-color: var(--accent);
    transform: translateY(-2px);
}

/* --------------------------------------------------------------------------
   Replicated Portfolio Footer
   -------------------------------------------------------------------------- */
.footer {
    margin-top: auto;
    background: var(--bg-glass);
    border-top: 1px solid var(--border-subtle);
    backdrop-filter: blur(14px);
    -webkit-backdrop-filter: blur(14px);
    padding: 2.25rem 0 1.75rem;
    position: relative;
    z-index: 10;
}

.footer-container {
    width: 100%;
    max-width: var(--max-width);
    margin: 0 auto;
    padding: 0 1.5rem;
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 2rem;
    flex-wrap: wrap;
}

.footer-left {
    display: flex;
    flex-direction: column;
    gap: 0.35rem;
    max-width: 340px;
}

.footer-tagline {
    font-size: 0.82rem;
    color: var(--text-muted);
    line-height: 1.45;
}

.footer-center {
    display: flex;
    flex-direction: column;
    align-items: flex-end;
    gap: 0.75rem;
    text-align: right;
}

.footer-nav {
    display: flex;
    align-items: center;
    gap: 1.25rem;
    flex-wrap: wrap;
    font-size: 0.85rem;
    font-weight: 500;
}

.footer-nav a {
    color: var(--text-secondary);
    transition: color var(--transition-fast);
}

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

.footer-copy {
    font-size: 0.8rem;
    color: var(--text-muted);
}

/* --------------------------------------------------------------------------
   Responsive Breakpoints
   -------------------------------------------------------------------------- */
@media (max-width: 1024px) {
    .note-container {
        grid-template-columns: 1fr;
    }

    .note-sidebar {
        display: none;
    }
}

@media (max-width: 768px) {
    #app {
        padding: 1.25rem 1rem 3rem;
    }

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

    .hero-section {
        padding: 2rem 0.5rem 1.5rem;
    }

    .markdown-body {
        padding: 1.5rem 1.25rem;
    }

    .note-pagination {
        grid-template-columns: 1fr;
    }

    .pagination-card.next {
        text-align: left;
        align-items: flex-start;
    }

    /* Centered Responsive Footer */
    .footer-container {
        flex-direction: column;
        align-items: center;
        text-align: center;
        gap: 1.75rem;
    }

    .footer-left {
        align-items: center;
        text-align: center;
        max-width: 100%;
    }

    .footer-tagline {
        text-align: center;
        max-width: 480px;
        margin: 0 auto;
    }

    .footer-center {
        align-items: center;
        text-align: center;
        width: 100%;
    }

    .footer-nav {
        justify-content: center;
        gap: 0.85rem 1.25rem;
        text-align: center;
    }

    .footer-copy {
        text-align: center;
    }

    /* Floating hovering button is active in all views with responsive offset */
    .back-to-top-btn {
        bottom: 1.25rem;
        right: 1.25rem;
        width: 42px;
        height: 42px;
    }

    .nav-search-btn kbd {
        display: none;
    }
}

@media (max-width: 640px) {
    /* Responsive Navbar: Text labels hidden, reducing to sleek icon buttons */
    .navbar-inner {
        padding: 0 1rem;
    }

    .navbar-brand, .brand-text {
        font-size: 1.15rem;
    }

    .navbar-actions {
        gap: 0.45rem;
    }

    .nav-link .nav-link-text {
        display: none;
    }

    .nav-link {
        width: 38px;
        height: 38px;
        padding: 0;
        justify-content: center;
        border-radius: var(--radius-md);
    }

    .nav-link svg {
        width: 17px;
        height: 17px;
    }

    .icon-btn {
        width: 38px;
        height: 38px;
    }

    /* Responsive Hero Search Bar */
    .hero-search-container {
        padding: 0;
        margin-top: 1.25rem;
    }

    .hero-search-bar {
        padding: 0.75rem 1rem;
        gap: 0.65rem;
    }

    .hero-search-text {
        font-size: 0.85rem;
    }

    .hero-search-shortcut {
        display: none;
    }
}

/* --------------------------------------------------------------------------
   Reduced Motion
   -------------------------------------------------------------------------- */
@media (prefers-reduced-motion: reduce) {
    *, *::before, *::after {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
        scroll-behavior: auto !important;
    }
}

/* --------------------------------------------------------------------------
   Print Stylesheet
   -------------------------------------------------------------------------- */
@media print {
    .navbar,
    .footer,
    .note-sidebar,
    .back-to-top-btn,
    #reading-progress,
    .note-pagination,
    .copy-code-btn,
    .back-btn,
    .toc-controls,
    .mark-done-btn,
    .edit-gh-badge,
    .search-modal-backdrop {
        display: none !important;
    }

    body {
        background: #fff !important;
        background-image: none !important;
        color: #000 !important;
    }

    #app {
        max-width: 100% !important;
        padding: 0 !important;
    }

    .markdown-body {
        background: transparent !important;
        border: none !important;
        box-shadow: none !important;
        padding: 0 !important;
        color: #000 !important;
    }

    .markdown-body a {
        color: #000 !important;
        text-decoration: underline !important;
    }

    details.diagram-source[open] pre, details.diagram-source pre {
        display: block !important;
    }
}