:root {
    --bg: #ffffff;
    --bg-soft: #f6f7f9;
    --fg: #1b1f24;
    --fg-muted: #5b6470;
    --accent: #2f5dd0;
    --accent-soft: #e8eefc;
    --border: #d8dee6;
    --code-bg: #f3f4f6;
    --sidebar-width: 20rem;
    --content-width: 46rem;
}

@media (prefers-color-scheme: dark) {
    :root {
        --bg: #12151a;
        --bg-soft: #181c22;
        --fg: #e6e9ee;
        --fg-muted: #9aa4b2;
        --accent: #7ea6ff;
        --accent-soft: #1d2637;
        --border: #2a313b;
        --code-bg: #1b2029;
    }
}

* {
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
}

body {
    margin: 0;
    background: var(--bg);
    color: var(--fg);
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    font-size: 17px;
    line-height: 1.65;
}

.layout {
    display: grid;
    grid-template-columns: var(--sidebar-width) minmax(0, 1fr);
    min-height: 100vh;
}

.sidebar {
    border-right: 1px solid var(--border);
    background: var(--bg-soft);
    padding: 1.75rem 1.25rem 3rem;
    position: sticky;
    top: 0;
    align-self: start;
    max-height: 100vh;
    overflow-y: auto;
}

.sidebar .brand {
    display: block;
    font-weight: 700;
    font-size: 1.15rem;
    color: var(--fg);
    text-decoration: none;
}

.sidebar .brand-sub {
    display: block;
    color: var(--fg-muted);
    font-size: 0.8rem;
    margin: 0.25rem 0 1.25rem;
}

.sidebar ol {
    list-style: none;
    margin: 0;
    padding: 0;
    counter-reset: chapter;
}

.sidebar li {
    margin: 0.15rem 0;
}

.sidebar a {
    display: block;
    padding: 0.3rem 0.5rem;
    border-radius: 6px;
    color: var(--fg-muted);
    text-decoration: none;
    font-size: 0.9rem;
}

.sidebar a:hover {
    background: var(--accent-soft);
    color: var(--accent);
}

.sidebar a[aria-current="page"] {
    background: var(--accent-soft);
    color: var(--accent);
    font-weight: 600;
}

.sidebar .part-label {
    margin: 1.25rem 0 0.35rem;
    padding: 0 0.5rem;
    font-size: 0.72rem;
    letter-spacing: 0.08em;
    text-transform: uppercase;
    color: var(--fg-muted);
}

.sidebar .download {
    display: inline-block;
    margin-top: 1.5rem;
    padding: 0.45rem 0.75rem;
    border: 1px solid var(--border);
    border-radius: 6px;
    font-size: 0.85rem;
    color: var(--accent);
    text-decoration: none;
}

main {
    padding: 2.5rem 3rem 5rem;
    max-width: calc(var(--content-width) + 6rem);
}

main > * {
    max-width: var(--content-width);
}

h1.title {
    font-size: 2.1rem;
    line-height: 1.2;
    margin: 0 0 1.5rem;
}

h1, h2, h3, h4 {
    line-height: 1.25;
    margin: 2.2rem 0 0.75rem;
}

h2 {
    font-size: 1.5rem;
    padding-bottom: 0.3rem;
    border-bottom: 1px solid var(--border);
}

h3 {
    font-size: 1.2rem;
}

h4 {
    font-size: 1.02rem;
    color: var(--fg-muted);
}

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

#TOC {
    margin: 0 0 2.5rem;
    padding: 1rem 1.25rem;
    background: var(--bg-soft);
    border: 1px solid var(--border);
    border-radius: 8px;
    font-size: 0.9rem;
}

#TOC ul {
    margin: 0.25rem 0;
    padding-left: 1.1rem;
}

code {
    font-family: ui-monospace, SFMono-Regular, "SF Mono", Menlo, Consolas, "DejaVu Sans Mono", monospace;
    font-size: 0.86em;
    background: var(--code-bg);
    padding: 0.12em 0.35em;
    border-radius: 4px;
}

pre, pre code {
    white-space: pre;
}

pre {
    background: var(--code-bg);
    border: 1px solid var(--border);
    border-radius: 8px;
    padding: 0.9rem 1rem;
    overflow-x: auto;
}

pre code {
    background: none;
    padding: 0;
    font-size: 0.82rem;
    line-height: 1.5;
}

table {
    border-collapse: collapse;
    width: 100%;
    margin: 1.25rem 0;
    font-size: 0.88rem;
    display: block;
    overflow-x: auto;
}

th, td {
    border: 1px solid var(--border);
    padding: 0.45rem 0.6rem;
    text-align: left;
    vertical-align: top;
}

th {
    background: var(--bg-soft);
}

blockquote {
    margin: 1.25rem 0;
    padding: 0.6rem 1rem;
    border-left: 4px solid var(--accent);
    background: var(--bg-soft);
    color: var(--fg-muted);
}

figure {
    margin: 1.75rem 0;
    max-width: 100%;
}

img {
    max-width: 100%;
    height: auto;
}

figcaption {
    color: var(--fg-muted);
    font-size: 0.82rem;
    margin-top: 0.4rem;
}

.diagram {
    background: #ffffff;
    border: 1px solid var(--border);
    border-radius: 8px;
    padding: 0.75rem;
    overflow-x: auto;
}

.pager {
    display: flex;
    justify-content: space-between;
    gap: 1rem;
    margin-top: 4rem;
    padding-top: 1.5rem;
    border-top: 1px solid var(--border);
    font-size: 0.9rem;
}

.pager a {
    text-decoration: none;
}

.pager .spacer {
    flex: 1;
}

.landing-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(15rem, 1fr));
    gap: 1rem;
    margin: 1.5rem 0;
    max-width: none;
}

.landing-grid a {
    display: block;
    padding: 1rem;
    border: 1px solid var(--border);
    border-radius: 8px;
    text-decoration: none;
    color: var(--fg);
    background: var(--bg-soft);
}

.landing-grid a:hover {
    border-color: var(--accent);
}

.landing-grid .num {
    display: block;
    font-size: 0.75rem;
    letter-spacing: 0.08em;
    text-transform: uppercase;
    color: var(--fg-muted);
}

.build-meta {
    color: var(--fg-muted);
    font-size: 0.82rem;
    margin-top: 3rem;
}

@media (max-width: 60rem) {
    .layout {
        grid-template-columns: 1fr;
    }

    .sidebar {
        position: static;
        max-height: none;
        border-right: none;
        border-bottom: 1px solid var(--border);
    }

    main {
        padding: 1.5rem 1.25rem 4rem;
    }
}