:root,
:root[data-theme="light"] {
    --bg: #ffffff;
    --fg: #1a1a1a;
    --muted: #6b7280;
    --border: #e5e7eb;
    --sidebar-bg: #fafafa;
    --accent: #2563eb;
    --accent-soft: rgba(37, 99, 235, 0.08);
    --code-bg: #f3f4f6;
    --code-border: #e5e7eb;
    --pre-bg: #f6f8fa;
    --pre-fg: #1f2328;
    --pre-border: #e5e7eb;
    --syn-comment: #6e7781;
    --syn-keyword: #cf222e;
    --syn-string: #0a3069;
    --syn-constant: #0550ae;
    --syn-function: #8250df;
    --syn-tag: #116329;
    --syn-variable: #953800;
    --blockquote-bg: #f9fafb;
    --blockquote-fg: #374151;
    --nav-link: #4b5563;
    --hover-bg: rgba(0, 0, 0, 0.04);
    --sidebar-width: 260px;
    --toc-width: 220px;
    --topbar-height: 56px;
    --content-max: 820px;
    --layout-max: 1400px;
    --mono: 'SF Mono', 'Fira Code', ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, 'Liberation Mono', 'Courier New', monospace;
    --sans: -apple-system, BlinkMacSystemFont, 'Inter', 'Segoe UI', 'Helvetica Neue', Arial, sans-serif;
    --brand-font: 'Space Grotesk', var(--sans);
}

:root[data-theme="dark"] {
    --bg: #0f1115;
    --fg: #e6e8ec;
    --muted: #8b93a1;
    --border: #242832;
    --sidebar-bg: #0b0d12;
    --accent: #6ea8fe;
    --accent-soft: rgba(110, 168, 254, 0.14);
    --code-bg: #1a1d24;
    --code-border: #262a33;
    --pre-bg: #0d1117;
    --pre-fg: #e6edf3;
    --pre-border: #262a33;
    --syn-comment: #8b949e;
    --syn-keyword: #ff7b72;
    --syn-string: #a5d6ff;
    --syn-constant: #79c0ff;
    --syn-function: #d2a8ff;
    --syn-tag: #7ee787;
    --syn-variable: #ffa657;
    --blockquote-bg: #14171e;
    --blockquote-fg: #b8bec9;
    --nav-link: #a3aab8;
    --hover-bg: rgba(255, 255, 255, 0.05);
}

* { box-sizing: border-box; }

html, body {
    margin: 0;
    padding: 0;
    background: var(--bg);
    color: var(--fg);
    font-family: var(--sans);
    font-size: 16px;
    line-height: 1.65;
    -webkit-font-smoothing: antialiased;
}

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

.layout {
    display: flex;
    gap: 2rem;
    align-items: flex-start;
    max-width: var(--layout-max);
    margin: 0 auto;
    padding: 1rem 1rem 0;
    padding-top: calc(var(--topbar-height) + 1rem);
    min-height: 100vh;
}

/* ---------- topbar ---------- */
.topbar {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    height: var(--topbar-height);
    background: var(--bg);
    border-bottom: 1px solid var(--border);
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 0 max(1rem, calc(50% - var(--layout-max) / 2 + 1rem));
    z-index: 10;
}

.topbar-left {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    min-width: 0;
}

.topbar .brand {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
}

.menu-toggle {
    display: none;
    appearance: none;
    background: transparent;
    border: 1px solid var(--border);
    color: var(--muted);
    border-radius: 6px;
    padding: 0.35rem 0.45rem;
    cursor: pointer;
    align-items: center;
    justify-content: center;
    line-height: 0;
    transition: color 0.1s, border-color 0.1s, background 0.1s;
}
.menu-toggle:hover {
    color: var(--fg);
    background: var(--hover-bg);
}
.menu-toggle .menu-icon-close { display: none; }
.menu-toggle.open .menu-icon-open { display: none; }
.menu-toggle.open .menu-icon-close { display: inline; }

.sidebar-backdrop {
    display: none;
    position: fixed;
    inset: 0;
    background: rgba(0, 0, 0, 0.4);
    z-index: 15;
    opacity: 0;
    transition: opacity 0.2s ease;
}
.sidebar-backdrop.open {
    display: block;
    opacity: 1;
}
.topbar .brand:hover { text-decoration: none; }

.brand-logo {
    height: 22px;
    width: auto;
    display: none;
}
:root[data-theme="light"] .brand-logo-light,
:root:not([data-theme="dark"]):not([data-theme="light"]) .brand-logo-light { display: inline; }
:root[data-theme="dark"] .brand-logo-dark { display: inline; }

.topbar .logo {
    color: var(--fg);
    font-family: var(--brand-font);
    font-weight: 600;
    font-size: 1rem;
    letter-spacing: 0.4px;
    line-height: 1;
}

.topbar .tagline {
    color: var(--muted);
    font-size: 0.8rem;
    font-weight: 500;
    text-transform: lowercase;
    letter-spacing: 0.02em;
    line-height: 1;
    transform: translateY(-2px);
}

.topbar-actions {
    display: flex;
    align-items: center;
    gap: 0.75rem;
}

.topbar-link {
    color: var(--muted);
    font-size: 0.9rem;
    font-weight: 500;
}
.topbar-link:hover { color: var(--fg); text-decoration: none; }

/* ---------- sidebar ---------- */
.sidebar {
    width: var(--sidebar-width);
    flex-shrink: 0;
    position: sticky;
    top: calc(var(--topbar-height) + 2.5rem);
    margin-top: 1.5rem;
    max-height: calc(100vh - var(--topbar-height) - 3.5rem);
    background: var(--sidebar-bg);
    border: 1px solid var(--border);
    border-radius: 12px;
    padding: 1.5rem 1.25rem;
    overflow-y: auto;
    display: flex;
    flex-direction: column;
    box-shadow: 0 4px 20px rgba(0, 0, 0, 0.04);
}

.sidebar nav {
    display: flex;
    flex-direction: column;
    gap: 0.1rem;
    flex: 1;
}

.sidebar nav a {
    display: block;
    color: var(--nav-link);
    padding: 0.4rem 0.6rem;
    border-radius: 5px;
    font-size: 0.92rem;
    font-weight: 500;
    transition: background 0.1s, color 0.1s;
}
.sidebar nav a:hover {
    color: var(--fg);
    background: var(--hover-bg);
    text-decoration: none;
}
.sidebar nav a.active {
    color: var(--accent);
    background: var(--accent-soft);
}

.sidebar .nav-section {
    color: var(--muted);
    font-size: 0.72rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.06em;
    padding: 1.25rem 0.6rem 0.4rem;
}

.site-footer {
    margin-top: 4rem;
    padding: 1.5rem 0;
    font-size: 0.8rem;
    color: var(--muted);
    border-top: 1px solid var(--border);
    max-width: var(--content-max);
}
.site-footer a {
    color: var(--muted);
    font-weight: 500;
}
.site-footer a:hover {
    color: var(--fg);
}

.theme-toggle {
    appearance: none;
    background: transparent;
    border: 1px solid var(--border);
    color: var(--muted);
    border-radius: 6px;
    padding: 0.3rem 0.4rem;
    cursor: pointer;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    line-height: 0;
    transition: color 0.1s, border-color 0.1s, background 0.1s;
}
.theme-toggle:hover {
    color: var(--fg);
    background: var(--hover-bg);
}
.theme-toggle .theme-icon { display: none; }
:root[data-theme="light"] .theme-toggle .theme-icon-moon { display: inline; }
:root[data-theme="dark"] .theme-toggle .theme-icon-sun { display: inline; }
:root:not([data-theme="dark"]):not([data-theme="light"]) .theme-toggle .theme-icon-moon { display: inline; }

/* ---------- content ---------- */
.content {
    flex: 1;
    min-width: 0;
    padding: 2rem 1rem 5rem;
}

#page-content {
    max-width: var(--content-max);
}

#page-content img {
    display: block;
    max-width: 100%;
    height: auto;
    margin: 1.75rem auto;
    border: 1px solid var(--border);
    border-radius: 8px;
    cursor: zoom-in;
    transition: opacity 0.15s;
}
#page-content img:hover { opacity: 0.92; }

.lightbox {
    position: fixed;
    inset: 0;
    background: rgba(0, 0, 0, 0.82);
    backdrop-filter: blur(4px);
    z-index: 100;
    display: none;
    align-items: center;
    justify-content: center;
    padding: 2rem;
    cursor: zoom-out;
    opacity: 0;
    transition: opacity 0.15s ease;
}
.lightbox.open {
    display: flex;
    opacity: 1;
}
.lightbox-img {
    max-width: 100%;
    max-height: 100%;
    object-fit: contain;
    border-radius: 8px;
    box-shadow: 0 20px 60px rgba(0, 0, 0, 0.5);
}
.lightbox-close {
    position: absolute;
    top: 1rem;
    right: 1rem;
    width: 36px;
    height: 36px;
    border: none;
    background: rgba(255, 255, 255, 0.1);
    color: #fff;
    border-radius: 50%;
    cursor: pointer;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    line-height: 0;
    transition: background 0.15s;
}
.lightbox-close:hover { background: rgba(255, 255, 255, 0.2); }

/* typography */
#page-content h1,
#page-content h2,
#page-content h3,
#page-content h4,
#page-content h5,
#page-content h6 {
    font-weight: 700;
    line-height: 1.25;
    margin: 2em 0 0.6em;
    letter-spacing: -0.01em;
}
#page-content h1 { font-size: 2.25rem; margin-top: 0; letter-spacing: -0.02em; }
#page-content h2 { font-size: 1.5rem; padding-bottom: 0.35em; border-bottom: 1px solid var(--border); }
#page-content h3 { font-size: 1.2rem; }
#page-content h4 { font-size: 1.05rem; }

#page-content p { margin: 1em 0; }

#page-content hr {
    border: none;
    border-top: 1px solid var(--border);
    margin: 2.5em 0;
}

#page-content ul,
#page-content ol { padding-left: 1.5em; }
#page-content li { margin: 0.25em 0; }
#page-content li > p { margin: 0.25em 0; }

#page-content blockquote {
    margin: 1.25em 0;
    padding: 0.5em 1em;
    border-left: 3px solid var(--accent);
    background: var(--blockquote-bg);
    color: var(--blockquote-fg);
}
#page-content blockquote p:first-child { margin-top: 0; }
#page-content blockquote p:last-child { margin-bottom: 0; }

/* code */
#page-content code {
    font-family: var(--mono);
    font-size: 0.875em;
    background: var(--code-bg);
    border: 1px solid var(--code-border);
    border-radius: 4px;
    padding: 0.1em 0.35em;
}

#page-content pre {
    background: var(--pre-bg);
    color: var(--pre-fg);
    border: 1px solid var(--pre-border);
    padding: 1rem 1.15rem;
    border-radius: 8px;
    overflow-x: auto;
    line-height: 1.55;
    margin: 1.25em 0;
    font-size: 0.9em;
}
#page-content pre code {
    background: transparent;
    border: none;
    padding: 0;
    font-size: 1em;
    color: inherit;
}

/* tables */
#page-content table {
    border-collapse: collapse;
    width: 100%;
    margin: 1.25em 0;
    font-size: 0.94em;
}
#page-content th,
#page-content td {
    padding: 0.55rem 0.85rem;
    border: 1px solid var(--border);
    text-align: left;
    vertical-align: top;
}
#page-content th {
    background: var(--sidebar-bg);
    font-weight: 600;
}

/* first-element top spacing fix */
#page-content > :first-child { margin-top: 0; }

/* ---------- floating TOC ---------- */
.toc-float {
    position: sticky;
    top: calc(var(--topbar-height) + 2.5rem);
    margin-top: 1.5rem;
    width: var(--toc-width);
    flex-shrink: 0;
    align-self: flex-start;
    max-height: calc(100vh - var(--topbar-height) - 3.5rem);
    overflow-y: auto;
    padding-left: 1rem;
    border-left: 1px solid var(--border);
}

.toc-float .toc-title {
    color: var(--muted);
    font-size: 0.7rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.06em;
    margin-bottom: 0.55rem;
}

.toc-float .toc-list {
    list-style: none;
    margin: 0;
    padding: 0;
    display: flex;
    flex-direction: column;
    gap: 0.05rem;
}

.toc-float .toc-list li { margin: 0; }
.toc-float .toc-list .toc-l3 a { padding-left: 1.35rem; }

.toc-float .toc-list a {
    display: block;
    padding: 0.28rem 0.55rem;
    color: var(--nav-link);
    border-radius: 5px;
    font-size: 0.85rem;
    line-height: 1.4;
    transition: background 0.1s, color 0.1s;
}
.toc-float .toc-list a:hover {
    color: var(--fg);
    background: var(--hover-bg);
    text-decoration: none;
}
.toc-float .toc-list a.active {
    color: var(--accent);
    background: var(--accent-soft);
}

/* Hide TOC when the viewport is not wide enough to fit it beside the content */
@media (max-width: 1100px) {
    .toc-float { display: none; }
}

/* ---------- responsive ---------- */
@media (max-width: 900px) {
    .topbar { padding: 0 1rem; }
    .topbar-link { display: none; }
    .menu-toggle { display: inline-flex; }

    .layout {
        flex-direction: column;
        gap: 0;
        padding: 0;
        padding-top: var(--topbar-height);
    }

    .sidebar {
        position: fixed;
        top: var(--topbar-height);
        left: 0;
        bottom: 0;
        width: min(85vw, 300px);
        max-height: none;
        border: none;
        border-right: 1px solid var(--border);
        border-radius: 0;
        box-shadow: 2px 0 20px rgba(0, 0, 0, 0.08);
        padding: 1.25rem 1.25rem;
        transform: translateX(-100%);
        transition: transform 0.2s ease;
        z-index: 20;
    }
    .sidebar.open { transform: translateX(0); }
    .sidebar nav { flex: none; }

    body.menu-open { overflow: hidden; }

    .content {
        padding: 2rem 1.25rem 3rem;
    }
    #page-content h1 { font-size: 1.85rem; }
}