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

:root {
    --bg: #0f1117;
    --surface: #161b22;
    --surface-alt: #1c2128;
    --border: #30363d;
    --text: #e8e8e4;
    --muted: #8b949e;
    --accent: #f59e0b;
    --accent-dark: #d97706;
    --mono: 'Courier New', Courier, monospace;
    --sidebar-width: 220px;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', system-ui, sans-serif;
    background-color: var(--bg);
    color: var(--text);
    line-height: 1.6;
    font-size: 15px;
    overflow-wrap: break-word;
}

code, .code-inline {
    word-break: break-word;
}

header {
    background-color: var(--surface);
    border-bottom: 1px solid var(--border);
    padding: 3rem 2rem;
    text-align: center;
    margin-left: var(--sidebar-width);
}

.badge {
    display: inline-block;
    background-color: var(--surface-alt);
    border: 1px solid var(--border);
    color: var(--muted);
    padding: 0.5rem 1rem;
    border-radius: 0.25rem;
    font-size: 0.85rem;
    font-family: var(--mono);
    margin-bottom: 1rem;
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

h1 {
    font-size: 3rem;
    font-weight: 700;
    margin-bottom: 0.5rem;
    color: var(--accent);
    letter-spacing: -0.02em;
}

h1 a {
    color: inherit;
    text-decoration: none;
}

h1 a:hover {
    text-decoration: underline;
}

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

a:hover {
    text-decoration: underline;
}

.subtitle {
    font-size: 1.25rem;
    color: var(--muted);
    margin-bottom: 1.5rem;
}

.tagline {
    font-family: var(--mono);
    font-size: 0.9rem;
    color: var(--muted);
    letter-spacing: 0.05em;
}

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

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

.breadcrumb {
    font-family: var(--mono);
    font-size: 0.78rem;
    color: var(--muted);
    margin-top: 0.9rem;
}

.breadcrumb a {
    color: var(--muted);
    text-decoration: none;
}

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

.breadcrumb .sep {
    margin: 0 0.35rem;
    opacity: 0.45;
}

.breadcrumb .current {
    color: var(--text);
}

.description {
    font-size: 1.05rem;
    line-height: 1.6;
    color: var(--text);
    margin-bottom: 1rem;
    font-weight: 400;
    margin-top: 1rem;
}

.page-layout {
    max-width: 980px;
    margin: 0 0 0 var(--sidebar-width);
    padding: 0 2rem;
    display: block;
}

main {
    min-width: 0;
    padding: 2rem 0;
}

.sidebar {
    width: var(--sidebar-width);
    position: fixed;
    left: 0;
    top: 0;
    bottom: 0;
    z-index: 10;
    max-height: 100vh;
    overflow-y: auto;
    padding: 1rem 0.75rem 1.25rem;
    background: var(--surface);
    border-right: 1px solid var(--border);
}

.tree { list-style: none; margin: 0; padding: 0; }
.tree-children { list-style: none; margin: 0; padding-left: 0.75rem; }

.tree-link {
    display: block;
    padding: 0.3rem 0.75rem;
    color: var(--muted);
    font-size: 0.85rem;
    line-height: 1.4;
    border-left: 2px solid transparent;
    text-decoration: none;
    transition: color 0.15s, border-color 0.15s;
}
.tree-link:hover { color: var(--text); text-decoration: none; }
.tree-link.active { color: var(--accent); border-left-color: var(--accent); }

.tree > .tree-group > .tree-link {
    font-size: 0.72rem;
    text-transform: uppercase;
    letter-spacing: 0.07em;
    font-weight: 600;
    padding-top: 1rem;
    padding-bottom: 0.1rem;
}
.tree > .tree-group:first-child > .tree-link { padding-top: 0.3rem; }

section {
    margin-bottom: 3rem;
}

section > h2 {
    font-size: 1.5rem;
    color: var(--accent);
    margin-bottom: 1.5rem;
    padding-bottom: 0.75rem;
    border-bottom: 2px solid var(--border);
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.abstract {
    background-color: var(--surface-alt);
    border-left: 3px solid var(--accent);
    padding: 1.5rem;
    border-radius: 0.25rem;
    margin-bottom: 2.5rem;
}

.abstract p {
    margin-bottom: 1rem;
    color: var(--text);
}

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

.doc-section {
    background-color: var(--surface-alt);
    border: 1px solid var(--border);
    padding: 1.5rem;
    margin-bottom: 1.5rem;
    border-radius: 0.25rem;
}

.doc-group {
    margin-bottom: 3rem;
}

.doc-group:last-child {
    margin-bottom: 0;
}

.doc-group-heading {
    color: var(--accent);
    font-size: 1.25rem;
    margin-bottom: 0.5rem;
    font-weight: 700;
    letter-spacing: 0.01em;
}

.doc-group-intro {
    color: var(--muted);
    margin-bottom: 1.25rem;
    line-height: 1.7;
    max-width: 72ch;
}

.doc-section h3 {
    color: var(--accent);
    font-size: 1.1rem;
    margin-bottom: 0.75rem;
    font-weight: 600;
}

.doc-section .doc-type {
    display: inline-block;
    background-color: var(--bg);
    color: var(--muted);
    padding: 0.25rem 0.75rem;
    border-radius: 0.2rem;
    font-family: var(--mono);
    font-size: 0.8rem;
    margin-bottom: 0.75rem;
}

.doc-section p {
    margin-bottom: 0.75rem;
    color: var(--muted);
    line-height: 1.7;
}

.doc-section p:last-child {
    margin-bottom: 0;
}

.doc-section ul {
    margin: 0.75rem 0 0.75rem 1.5rem;
    color: var(--muted);
}

.doc-section li {
    margin-bottom: 0.5rem;
}

.doc-actions {
    display: flex;
    gap: 0.75rem;
    margin-top: 1.25rem;
    padding-top: 1rem;
    border-top: 1px solid var(--border);
}

.doc-link {
    display: inline-block;
    padding: 0.5rem 1rem;
    background-color: var(--bg);
    border: 1px solid var(--accent);
    color: var(--accent);
    text-decoration: none;
    border-radius: 0.2rem;
    font-family: var(--mono);
    font-size: 0.85rem;
    transition: all 0.2s ease;
}

.doc-link:hover {
    background-color: var(--accent);
    color: var(--bg);
}

.code-inline {
    font-family: var(--mono);
    background-color: var(--bg);
    padding: 0.2rem 0.4rem;
    border-radius: 0.2rem;
    color: var(--accent);
}

.model-section {
    background-color: var(--surface-alt);
    border: 2px solid var(--accent);
    padding: 2rem;
    border-radius: 0.25rem;
    text-align: center;
}

.model-section p {
    color: var(--muted);
    margin-bottom: 1.5rem;
    line-height: 1.7;
}

.cta-button {
    display: inline-block;
    background-color: var(--accent);
    color: var(--bg);
    padding: 0.75rem 2rem;
    font-size: 1rem;
    border-radius: 0.25rem;
    text-decoration: none;
    font-weight: 600;
    transition: background-color 0.2s ease;
}

.cta-button:hover {
    background-color: var(--accent-dark);
}

.standards {
    background-color: var(--surface-alt);
    padding: 1.5rem;
    border: 1px solid var(--border);
    border-radius: 0.25rem;
}

.standards-tags {
    display: flex;
    flex-wrap: wrap;
    gap: 1rem;
    margin-top: 1rem;
}

.standard-tag {
    background-color: var(--bg);
    color: var(--accent);
    padding: 0.5rem 1rem;
    border: 1px solid var(--accent);
    border-radius: 0.25rem;
    font-family: var(--mono);
    font-size: 0.9rem;
    text-decoration: none;
    display: inline-block;
    transition: all 0.2s ease;
}

a.standard-tag:hover {
    background-color: var(--accent);
    color: var(--bg);
}

footer {
    border-top: 1px solid var(--border);
    padding: 2rem;
    margin-top: 3rem;
    text-align: center;
    color: var(--muted);
    font-size: 0.9rem;
}

footer p {
    margin-bottom: 0.5rem;
}

.reading-path {
    background: var(--surface);
    border-left: 4px solid var(--accent);
    padding: 1.5rem;
    border-radius: 0.25rem;
}

.path-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
    gap: 1rem;
    margin-top: 1.5rem;
}

.path-card {
    display: block;
    padding: 1rem;
    border: 1px solid var(--border);
    border-radius: 4px;
    text-decoration: none;
    color: var(--accent);
    transition: background 0.15s, border-color 0.15s;
}
.path-card:hover { background: var(--surface-alt); border-color: var(--accent); text-decoration: none; }
.path-card p { margin: 0.5rem 0 0; font-size: 0.85rem; color: var(--muted); }

@media (max-width: 900px) {
    header { margin-left: 0; }
    .page-layout { margin-left: 0; padding: 0 1rem; }
    .sidebar { display: none; }
    main { padding: 1.5rem 0; }
    h1 { font-size: 2rem; }
    .subtitle { font-size: 1rem; }
    header { padding: 2rem 1rem; }
}

@media (max-width: 600px) {
    .abstract { padding: 1rem; }
    .doc-section { padding: 1rem; }
    .reading-path { padding: 1rem; }
    .model-section { padding: 1.25rem; }
    .cta-button { display: block; text-align: center; }
    .doc-actions { flex-wrap: wrap; }
}

#back-to-top {
    position: fixed;
    right: 20px;
    bottom: 20px;
    z-index: 1000;
    border: 1px solid var(--accent);
    background: var(--surface-alt);
    color: var(--accent);
    padding: 0.5rem 0.8rem;
    border-radius: 0.25rem;
    font-family: var(--mono);
    font-size: 0.8rem;
    cursor: pointer;
    opacity: 0;
    pointer-events: none;
    transition: opacity 0.2s ease, transform 0.2s ease;
    transform: translateY(6px);
}

#back-to-top.visible {
    opacity: 1;
    pointer-events: auto;
    transform: translateY(0);
}