/* ============================================================
   ronri.org — Logic Encyclopedia
   Three-column documentation layout
   Colors: #059669, #f3f4f6, #4f46e5, #f9fafb, #e5e7eb, #ffffff, #111827
   Fonts: Inter (headings), Source Serif 4 (body), Source Code Pro (code)
   ============================================================ */

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

:root {
    --color-emerald:    #059669;
    --color-indigo:     #4f46e5;
    --color-gray-50:    #f9fafb;
    --color-gray-100:   #f3f4f6;
    --color-gray-200:   #e5e7eb;
    --color-gray-900:   #111827;
    --color-white:      #ffffff;

    --color-text-primary:   #111827;
    --color-text-secondary: #374151;
    --color-text-muted:     #6b7280;
    --color-border:         #e5e7eb;

    --font-heading: 'Inter', system-ui, -apple-system, sans-serif;
    --font-body:    'Source Serif 4', 'Georgia', serif;
    --font-code:    'Source Code Pro', 'Courier New', monospace;

    --header-height: 60px;
    --sidebar-left-width: 240px;
    --sidebar-right-width: 200px;
    --content-max-width: 800px;
}

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

body {
    font-family: var(--font-body);
    color: var(--color-text-primary);
    background-color: var(--color-white);
    line-height: 1.8;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

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

/* --- Site Header --- */
#site-header {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    height: var(--header-height);
    background: var(--color-white);
    border-bottom: 1px solid var(--color-border);
    z-index: 100;
    transition: box-shadow 0.2s ease;
}

#site-header.scrolled {
    box-shadow: 0 1px 8px rgba(17, 24, 39, 0.08);
}

.header-inner {
    display: flex;
    align-items: center;
    max-width: 1280px;
    margin: 0 auto;
    padding: 0 24px;
    height: 100%;
    gap: 32px;
}

.site-logo {
    display: flex;
    align-items: center;
    gap: 8px;
    text-decoration: none;
    flex-shrink: 0;
}

.logo-symbol {
    font-family: var(--font-code);
    font-size: 1.25rem;
    color: var(--color-indigo);
    font-weight: 500;
    line-height: 1;
}

.logo-text {
    font-family: var(--font-heading);
    font-weight: 700;
    font-size: 1.1rem;
    color: var(--color-gray-900);
    letter-spacing: -0.02em;
}

.logo-dot {
    color: var(--color-indigo);
}

.header-nav {
    display: flex;
    align-items: center;
    gap: 4px;
    flex-shrink: 0;
}

.header-nav .nav-link {
    font-family: var(--font-heading);
    font-size: 0.875rem;
    font-weight: 500;
    color: var(--color-text-muted);
    padding: 6px 12px;
    border-radius: 6px;
    transition: color 0.15s ease, background-color 0.15s ease;
}

.header-nav .nav-link:hover {
    color: var(--color-gray-900);
    background-color: var(--color-gray-100);
}

.header-nav .nav-link.active {
    color: var(--color-indigo);
    background-color: rgba(79, 70, 229, 0.06);
}

.header-search {
    margin-left: auto;
    flex-shrink: 0;
}

.search-box {
    display: flex;
    align-items: center;
    gap: 8px;
    background: var(--color-gray-100);
    border: 1px solid var(--color-border);
    border-radius: 8px;
    padding: 7px 12px;
    cursor: pointer;
    transition: border-color 0.15s ease, background-color 0.15s ease;
    min-width: 220px;
}

.search-box:hover {
    background: var(--color-white);
    border-color: var(--color-indigo);
}

.search-icon {
    width: 16px;
    height: 16px;
    color: var(--color-text-muted);
    flex-shrink: 0;
}

.search-input {
    border: none;
    outline: none;
    background: transparent;
    font-family: var(--font-heading);
    font-size: 0.875rem;
    color: var(--color-text-primary);
    flex: 1;
    cursor: pointer;
}

.search-input::placeholder {
    color: var(--color-text-muted);
}

.search-kbd {
    font-family: var(--font-heading);
    font-size: 0.75rem;
    color: var(--color-text-muted);
    background: var(--color-white);
    border: 1px solid var(--color-border);
    border-radius: 4px;
    padding: 1px 5px;
    flex-shrink: 0;
}

/* --- Page Layout: Three-column grid --- */
.page-layout {
    display: grid;
    grid-template-columns: var(--sidebar-left-width) 1fr var(--sidebar-right-width);
    max-width: 1280px;
    margin: 0 auto;
    margin-top: var(--header-height);
    min-height: calc(100vh - var(--header-height));
}

/* --- Left Sidebar --- */
.sidebar-left {
    position: sticky;
    top: var(--header-height);
    height: calc(100vh - var(--header-height));
    overflow-y: auto;
    border-right: 1px solid var(--color-border);
    padding: 24px 0 48px;
    background: var(--color-gray-50);
}

.sidebar-left::-webkit-scrollbar {
    width: 4px;
}
.sidebar-left::-webkit-scrollbar-track {
    background: transparent;
}
.sidebar-left::-webkit-scrollbar-thumb {
    background: var(--color-gray-200);
    border-radius: 2px;
}

.sidebar-nav {
    padding: 0;
}

.nav-section {
    margin-bottom: 4px;
}

.nav-section-title {
    font-family: var(--font-heading);
    font-size: 0.7rem;
    font-weight: 600;
    letter-spacing: 0.08em;
    text-transform: uppercase;
    color: var(--color-text-muted);
    padding: 8px 20px 4px;
    display: block;
}

.nav-collapsible {
    border: none;
}

.nav-collapsible-title {
    cursor: pointer;
    list-style: none;
    user-select: none;
    transition: color 0.15s ease;
}

.nav-collapsible-title::-webkit-details-marker {
    display: none;
}

.nav-collapsible-title::before {
    content: '›';
    display: inline-block;
    margin-right: 6px;
    font-size: 0.8rem;
    transition: transform 0.2s ease;
    color: var(--color-text-muted);
}

details[open] .nav-collapsible-title::before {
    transform: rotate(90deg);
}

.nav-tree {
    list-style: none;
    padding: 0;
}

.nav-subtree {
    list-style: none;
    padding: 0;
    margin: 2px 0;
}

.nav-item {
    display: block;
}

.nav-link-tree {
    font-family: var(--font-heading);
    font-size: 0.8125rem;
    color: var(--color-text-secondary);
    display: block;
    padding: 5px 20px;
    transition: color 0.15s ease, background-color 0.15s ease;
    border-right: 3px solid transparent;
}

.nav-link-tree:hover {
    color: var(--color-gray-900);
    background-color: var(--color-gray-100);
}

.nav-link-tree--active {
    color: var(--color-gray-900);
    font-weight: 600;
}

.nav-link-tree--sub {
    padding-left: 36px;
    font-size: 0.8rem;
}

.nav-link-tree--current {
    background-color: rgba(79, 70, 229, 0.08);
    border-right-color: var(--color-indigo);
    color: var(--color-indigo);
    font-weight: 500;
}

/* --- Main Content --- */
.main-content {
    padding: 32px 48px 80px;
    max-width: var(--content-max-width);
    width: 100%;
    min-width: 0;
}

/* --- Breadcrumb --- */
.breadcrumb {
    margin-bottom: 24px;
}

.breadcrumb-list {
    list-style: none;
    display: flex;
    align-items: center;
    flex-wrap: wrap;
    gap: 4px;
}

.breadcrumb-item {
    font-family: var(--font-heading);
    font-size: 0.8125rem;
    color: var(--color-text-muted);
}

.breadcrumb-link {
    color: var(--color-text-muted);
    transition: color 0.15s ease;
}

.breadcrumb-link:hover {
    color: var(--color-indigo);
}

.breadcrumb-separator {
    color: var(--color-gray-200);
    font-size: 0.9rem;
    user-select: none;
}

.breadcrumb-item--current {
    font-weight: 600;
    color: var(--color-indigo);
}

/* --- Article Header --- */
.article-header {
    margin-bottom: 40px;
}

.article-meta {
    display: flex;
    align-items: center;
    gap: 8px;
    margin-bottom: 12px;
}

.article-tag {
    font-family: var(--font-heading);
    font-size: 0.75rem;
    font-weight: 600;
    color: var(--color-emerald);
    background: rgba(5, 150, 105, 0.08);
    padding: 3px 10px;
    border-radius: 999px;
    letter-spacing: 0.02em;
}

.article-meta-sep {
    color: var(--color-gray-200);
    font-size: 0.9rem;
}

.article-read-time {
    font-family: var(--font-heading);
    font-size: 0.8125rem;
    color: var(--color-text-muted);
}

.article-title {
    font-family: var(--font-heading);
    font-weight: 700;
    font-size: clamp(1.5rem, 3vw, 2rem);
    color: var(--color-gray-900);
    line-height: 1.2;
    letter-spacing: -0.025em;
    margin-bottom: 12px;
}

.article-subtitle {
    font-family: var(--font-body);
    font-size: 1.0625rem;
    color: var(--color-text-secondary);
    line-height: 1.7;
    max-width: 600px;
}

.article-divider {
    height: 1px;
    background: var(--color-border);
    margin-top: 28px;
}

/* --- Article Body --- */
.article-section {
    margin-bottom: 48px;
}

.section-heading {
    font-family: var(--font-heading);
    font-weight: 700;
    font-size: clamp(1.125rem, 2vw, 1.375rem);
    color: var(--color-gray-900);
    letter-spacing: -0.02em;
    margin-bottom: 16px;
    padding-top: 8px;
    scroll-margin-top: calc(var(--header-height) + 24px);
}

.subsection-heading {
    font-family: var(--font-heading);
    font-weight: 600;
    font-size: 0.9375rem;
    color: var(--color-gray-900);
    letter-spacing: -0.01em;
    margin: 24px 0 12px;
}

.body-text {
    font-family: var(--font-body);
    font-size: 1rem;
    line-height: 1.8;
    color: var(--color-text-secondary);
    margin-bottom: 16px;
}

.body-text:last-child {
    margin-bottom: 0;
}

em {
    font-style: italic;
    color: var(--color-gray-900);
}

strong {
    font-weight: 600;
    color: var(--color-gray-900);
}

/* --- Inline Code --- */
.inline-code {
    font-family: var(--font-code);
    font-size: 0.875em;
    color: var(--color-indigo);
    background: rgba(79, 70, 229, 0.06);
    padding: 1px 5px;
    border-radius: 4px;
    white-space: nowrap;
}

/* --- Notation Blocks (Logic Code Blocks) --- */
.notation-block {
    background: var(--color-gray-100);
    border-left: 3px solid var(--color-indigo);
    border-radius: 0 6px 6px 0;
    padding: 16px 20px;
    margin: 20px 0;
    overflow: hidden;
}

.notation-label {
    font-family: var(--font-heading);
    font-size: 0.6875rem;
    font-weight: 600;
    letter-spacing: 0.08em;
    text-transform: uppercase;
    color: var(--color-indigo);
    margin-bottom: 10px;
}

.notation-pre {
    margin: 0;
    overflow-x: auto;
}

.notation-code {
    font-family: var(--font-code);
    font-size: 0.875rem;
    line-height: 1.7;
    color: var(--color-gray-900);
    white-space: pre;
    display: block;
}

/* --- Callout Boxes --- */
.callout {
    display: flex;
    gap: 14px;
    border-radius: 8px;
    padding: 16px 18px;
    margin: 20px 0;
}

.callout--info {
    background: rgba(79, 70, 229, 0.05);
    border: 1px solid rgba(79, 70, 229, 0.15);
}

.callout--example {
    background: rgba(5, 150, 105, 0.05);
    border: 1px solid rgba(5, 150, 105, 0.2);
}

.callout--warning {
    background: rgba(245, 158, 11, 0.05);
    border: 1px solid rgba(245, 158, 11, 0.2);
}

.callout-icon {
    font-family: var(--font-code);
    font-size: 0.9375rem;
    font-weight: 600;
    flex-shrink: 0;
    width: 24px;
    height: 24px;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 50%;
    margin-top: 1px;
}

.callout--info .callout-icon {
    color: var(--color-indigo);
    background: rgba(79, 70, 229, 0.1);
}

.callout--example .callout-icon {
    color: var(--color-emerald);
    background: rgba(5, 150, 105, 0.1);
}

.callout--warning .callout-icon {
    color: #d97706;
    background: rgba(245, 158, 11, 0.1);
}

.callout-body {
    font-family: var(--font-body);
    font-size: 0.9375rem;
    line-height: 1.7;
    color: var(--color-text-secondary);
}

.callout-title {
    font-weight: 600;
    color: var(--color-gray-900);
}

/* --- Truth Tables --- */
.truth-table-wrapper {
    overflow-x: auto;
    margin: 16px 0 24px;
}

.truth-table {
    border-collapse: collapse;
    font-family: var(--font-code);
    font-size: 0.875rem;
    min-width: 200px;
}

.truth-table thead tr {
    background: var(--color-gray-100);
    border-bottom: 2px solid var(--color-border);
}

.truth-table th {
    font-family: var(--font-heading);
    font-weight: 600;
    font-size: 0.8125rem;
    color: var(--color-gray-900);
    padding: 8px 20px;
    text-align: center;
    border: 1px solid var(--color-border);
}

.truth-table td {
    padding: 7px 20px;
    text-align: center;
    border: 1px solid var(--color-border);
    color: var(--color-text-secondary);
    transition: background-color 0.1s ease;
}

.truth-table tbody tr:hover td {
    background: var(--color-gray-50);
}

.result-true {
    color: var(--color-emerald);
    font-weight: 600;
    background: rgba(5, 150, 105, 0.04);
}

.result-false {
    color: #dc2626;
    font-weight: 600;
    background: rgba(220, 38, 38, 0.04);
}

/* --- Related Pages Grid --- */
.related-pages {
    margin-top: 56px;
    padding-top: 32px;
    border-top: 1px solid var(--color-border);
}

.related-title {
    font-family: var(--font-heading);
    font-weight: 700;
    font-size: 1rem;
    color: var(--color-gray-900);
    margin-bottom: 16px;
    letter-spacing: -0.01em;
}

.related-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 12px;
}

.related-card {
    display: flex;
    align-items: flex-start;
    gap: 14px;
    padding: 16px;
    border: 1px solid var(--color-border);
    border-radius: 8px;
    background: var(--color-white);
    transition: border-color 0.15s ease, box-shadow 0.15s ease, transform 0.15s ease;
    text-decoration: none;
}

.related-card:hover {
    border-color: var(--color-indigo);
    box-shadow: 0 2px 12px rgba(79, 70, 229, 0.1);
    transform: translateY(-1px);
}

.related-card-symbol {
    font-family: var(--font-code);
    font-size: 1.25rem;
    color: var(--color-indigo);
    flex-shrink: 0;
    width: 32px;
    text-align: center;
    line-height: 1.4;
}

.related-card-title {
    font-family: var(--font-heading);
    font-weight: 600;
    font-size: 0.875rem;
    color: var(--color-gray-900);
    margin-bottom: 3px;
}

.related-card-desc {
    font-family: var(--font-heading);
    font-size: 0.8rem;
    color: var(--color-text-muted);
    line-height: 1.4;
}

/* --- Right Sidebar — Table of Contents --- */
.sidebar-right {
    position: sticky;
    top: var(--header-height);
    height: calc(100vh - var(--header-height));
    overflow-y: auto;
    padding: 32px 0 48px 16px;
    border-left: 1px solid var(--color-border);
}

.sidebar-right::-webkit-scrollbar {
    width: 4px;
}
.sidebar-right::-webkit-scrollbar-thumb {
    background: var(--color-gray-200);
    border-radius: 2px;
}

.toc-container {
    padding-right: 16px;
}

.toc-title {
    font-family: var(--font-heading);
    font-size: 0.6875rem;
    font-weight: 600;
    letter-spacing: 0.08em;
    text-transform: uppercase;
    color: var(--color-text-muted);
    margin-bottom: 12px;
}

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

.toc-item {
    margin-bottom: 2px;
}

.toc-link {
    font-family: var(--font-heading);
    font-size: 0.8rem;
    color: var(--color-text-muted);
    display: block;
    padding: 4px 8px;
    border-left: 2px solid transparent;
    border-radius: 0 4px 4px 0;
    transition: color 0.15s ease, border-color 0.15s ease, background-color 0.15s ease;
    line-height: 1.4;
}

.toc-link:hover {
    color: var(--color-gray-900);
    background: var(--color-gray-100);
}

.toc-link--active {
    color: var(--color-indigo);
    border-left-color: var(--color-indigo);
    background: rgba(79, 70, 229, 0.05);
    font-weight: 500;
}

.toc-progress {
    margin-top: 20px;
    height: 2px;
    background: var(--color-gray-200);
    border-radius: 1px;
    overflow: hidden;
}

.toc-progress-bar {
    height: 100%;
    background: linear-gradient(90deg, var(--color-indigo), var(--color-emerald));
    border-radius: 1px;
    width: 0%;
    transition: width 0.1s ease;
}

/* --- Search Overlay --- */
.search-overlay {
    position: fixed;
    inset: 0;
    background: rgba(17, 24, 39, 0.5);
    z-index: 200;
    display: flex;
    align-items: flex-start;
    justify-content: center;
    padding-top: 80px;
    opacity: 0;
    pointer-events: none;
    transition: opacity 0.2s ease;
    backdrop-filter: blur(2px);
}

.search-overlay.open {
    opacity: 1;
    pointer-events: all;
}

.search-modal {
    background: var(--color-white);
    border-radius: 12px;
    width: 560px;
    max-width: calc(100vw - 40px);
    box-shadow: 0 20px 60px rgba(17, 24, 39, 0.2);
    overflow: hidden;
    transform: translateY(-16px);
    transition: transform 0.2s ease;
}

.search-overlay.open .search-modal {
    transform: translateY(0);
}

.search-modal-header {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 16px 20px;
    border-bottom: 1px solid var(--color-border);
}

.search-modal-icon {
    width: 18px;
    height: 18px;
    color: var(--color-text-muted);
    flex-shrink: 0;
}

.search-modal-input {
    flex: 1;
    border: none;
    outline: none;
    font-family: var(--font-heading);
    font-size: 0.9375rem;
    color: var(--color-text-primary);
    background: transparent;
}

.search-modal-input::placeholder {
    color: var(--color-text-muted);
}

.search-modal-close {
    font-family: var(--font-heading);
    font-size: 0.75rem;
    color: var(--color-text-muted);
    background: var(--color-gray-100);
    border: 1px solid var(--color-border);
    border-radius: 4px;
    padding: 2px 6px;
    cursor: pointer;
    flex-shrink: 0;
    transition: background-color 0.15s ease;
}

.search-modal-close:hover {
    background: var(--color-gray-200);
}

.search-results {
    padding: 8px 0;
    max-height: 400px;
    overflow-y: auto;
}

.search-results-group {
    padding: 8px 0;
}

.search-results-label {
    font-family: var(--font-heading);
    font-size: 0.6875rem;
    font-weight: 600;
    letter-spacing: 0.08em;
    text-transform: uppercase;
    color: var(--color-text-muted);
    padding: 4px 20px 8px;
}

.search-result-item {
    display: flex;
    align-items: center;
    gap: 14px;
    padding: 10px 20px;
    transition: background-color 0.1s ease;
    cursor: pointer;
}

.search-result-item:hover {
    background: var(--color-gray-50);
}

.search-result-item.highlighted {
    background: rgba(79, 70, 229, 0.05);
}

.search-result-symbol {
    font-family: var(--font-code);
    font-size: 1.125rem;
    color: var(--color-indigo);
    width: 28px;
    text-align: center;
    flex-shrink: 0;
}

.search-result-title {
    font-family: var(--font-heading);
    font-size: 0.875rem;
    font-weight: 500;
    color: var(--color-gray-900);
    margin-bottom: 2px;
}

.search-result-desc {
    font-family: var(--font-heading);
    font-size: 0.8rem;
    color: var(--color-text-muted);
}

/* --- Scroll to top / sticky header behavior --- */
.article-section {
    scroll-margin-top: calc(var(--header-height) + 16px);
}

/* --- Responsive: hide sidebars on narrow screens --- */
@media (max-width: 1100px) {
    .page-layout {
        grid-template-columns: var(--sidebar-left-width) 1fr;
    }
    .sidebar-right {
        display: none;
    }
}

@media (max-width: 768px) {
    .page-layout {
        grid-template-columns: 1fr;
    }
    .sidebar-left {
        display: none;
    }
    .main-content {
        padding: 24px 20px 60px;
    }
    .related-grid {
        grid-template-columns: 1fr;
    }
    .header-nav {
        display: none;
    }
}