:root {
    color-scheme: dark;

    --bg: #0d1117;
    --surface: #131922;
    --surface-2: #18202b;
    --surface-3: #1e2835;
    --border: #232d3b;
    --border-strong: #33415a;
    --text: #e4e8ef;
    --text-soft: #c3cad6;
    --muted: #8c97a8;

    --accent: #7aa2f7;
    --accent-2: #bb9af7;
    --good: #9ece6a;
    --warn: #e0af68;
    --bad: #f7768e;
    --cyan: #7dcfff;
    --note-bg: #2a2418;

    --code-bg: #0f141c;
    --radius: 14px;
    --content: 840px;
    --topbar-h: 56px;

    --font: 'Inter', system-ui, -apple-system, 'Segoe UI', Roboto, sans-serif;
    --mono: 'JetBrains Mono', ui-monospace, 'SFMono-Regular', Consolas, monospace;
}

*,
*::before,
*::after { box-sizing: border-box; }

html { -webkit-text-size-adjust: 100%; scroll-padding-top: calc(var(--topbar-h) + 16px); }

body {
    margin: 0;
    min-height: 100vh;
    background:
        radial-gradient(1200px 600px at 85% -10%, rgba(122, 162, 247, 0.08), transparent 60%),
        radial-gradient(900px 500px at -10% 110%, rgba(187, 154, 247, 0.06), transparent 60%),
        var(--bg);
    background-attachment: fixed;
    color: var(--text);
    font: 16px/1.65 var(--font);
    -webkit-font-smoothing: antialiased;
}

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

::selection { background: rgba(122, 162, 247, 0.35); }

/* ---------- top bar ---------- */

.topbar {
    position: sticky;
    top: 0;
    z-index: 20;
    background: rgba(13, 17, 23, 0.82);
    backdrop-filter: saturate(1.4) blur(12px);
    -webkit-backdrop-filter: saturate(1.4) blur(12px);
    border-bottom: 1px solid var(--border);
}

.topbar__inner {
    display: flex;
    align-items: center;
    gap: 12px;
    max-width: calc(var(--content) + 32px);
    height: var(--topbar-h);
    margin: 0 auto;
    padding: 0 16px;
}

.topbar__brand {
    color: var(--text);
    font-weight: 600;
    letter-spacing: -0.01em;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}
.topbar__brand:hover { text-decoration: none; color: #fff; }

.topbar__spacer { flex: 1; }

.topbar__count {
    color: var(--muted);
    font: 500 13px var(--mono);
    white-space: nowrap;
}

.topbar__toc {
    padding: 6px 12px;
    border: 1px solid var(--border-strong);
    border-radius: 999px;
    color: var(--text-soft);
    font-size: 14px;
    white-space: nowrap;
    transition: border-color .15s, color .15s, background .15s;
}
.topbar__toc:hover { text-decoration: none; color: var(--text); border-color: var(--accent); background: rgba(122, 162, 247, 0.08); }

.badge {
    padding: 2px 10px;
    border-radius: 999px;
    font-size: 12px;
    font-weight: 600;
    letter-spacing: 0.02em;
    white-space: nowrap;
}
.badge--candidate { color: var(--cyan); background: rgba(125, 207, 255, 0.12); border: 1px solid rgba(125, 207, 255, 0.3); }
.badge--interviewer { color: var(--accent-2); background: rgba(187, 154, 247, 0.12); border: 1px solid rgba(187, 154, 247, 0.3); }

.progress { height: 2px; background: transparent; }
.progress span {
    display: block;
    height: 100%;
    background: linear-gradient(90deg, var(--accent), var(--accent-2));
    box-shadow: 0 0 12px rgba(122, 162, 247, 0.6);
}

/* ---------- layout ---------- */

.content {
    max-width: calc(var(--content) + 32px);
    margin: 0 auto;
    padding: 40px 16px 80px;
}

.eyebrow {
    margin: 0 0 8px;
    color: var(--muted);
    font-size: 13px;
    font-weight: 600;
    letter-spacing: 0.08em;
    text-transform: uppercase;
}

h1, h2, h3, h4 { letter-spacing: -0.015em; line-height: 1.25; }

.hero { margin-bottom: 28px; }
.hero h1 {
    margin: 0;
    font-size: clamp(32px, 6vw, 48px);
    font-weight: 700;
    background: linear-gradient(120deg, #fff 20%, var(--accent) 70%, var(--accent-2));
    -webkit-background-clip: text;
    background-clip: text;
    color: transparent;
}

.q-head { margin-bottom: 24px; }
.q-head h1 {
    display: flex;
    align-items: baseline;
    flex-wrap: wrap;
    gap: 12px;
    margin: 0 0 12px;
    font-size: clamp(26px, 4.5vw, 36px);
    font-weight: 700;
}

.q-num {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    min-width: 2.6em;
    padding: 0.15em 0.5em;
    border-radius: 10px;
    background: linear-gradient(135deg, rgba(122, 162, 247, 0.18), rgba(187, 154, 247, 0.18));
    border: 1px solid rgba(122, 162, 247, 0.35);
    color: var(--accent);
    font: 600 0.8em var(--mono);
    letter-spacing: 0;
}

.chips { display: flex; flex-wrap: wrap; gap: 8px; }
.chips:empty { display: none; }
.chip {
    padding: 2px 10px;
    border-radius: 999px;
    font-size: 12.5px;
    font-weight: 500;
    white-space: nowrap;
    border: 1px solid var(--border-strong);
    color: var(--text-soft);
}
.chip--required { color: var(--good); border-color: rgba(158, 206, 106, 0.4); background: rgba(158, 206, 106, 0.1); }
.chip--reserve { color: var(--muted); }
.chip--time { font-family: var(--mono); font-size: 12px; }

/* ---------- cards ---------- */

.card {
    position: relative;
    margin: 0 0 20px;
    padding: 28px 32px;
    background: linear-gradient(180deg, var(--surface-2), var(--surface));
    border: 1px solid var(--border);
    border-radius: var(--radius);
    box-shadow: 0 1px 0 rgba(255, 255, 255, 0.03) inset, 0 12px 32px rgba(0, 0, 0, 0.25);
}

.card--answer {
    border-color: rgba(158, 206, 106, 0.28);
    background: linear-gradient(180deg, #17221c, var(--surface) 240px);
}
.card--answer::before {
    content: '';
    position: absolute;
    inset: 0 auto 0 0;
    width: 3px;
    border-radius: var(--radius) 0 0 var(--radius);
    background: linear-gradient(180deg, var(--good), rgba(158, 206, 106, 0));
}

.section-title {
    display: flex;
    align-items: center;
    gap: 10px;
    margin: 0 0 16px !important;
    color: var(--muted);
    font-size: 13px !important;
    font-weight: 600;
    letter-spacing: 0.08em;
    text-transform: uppercase;
}
.card--answer .section-title { color: var(--good); }

/* ---------- prose ---------- */

.prose > :first-child { margin-top: 0; }
.prose > :last-child { margin-bottom: 0; }
.prose p, .prose ul, .prose ol { margin: 0 0 14px; color: var(--text-soft); }
.prose strong { color: var(--text); font-weight: 600; }
.prose h3 { margin: 28px 0 12px; font-size: 20px; }
.prose h4 { margin: 24px 0 10px; font-size: 17px; }
.prose ul, .prose ol { padding-left: 1.4em; }
.prose li { margin: 6px 0; }
.prose li::marker { color: var(--accent); }
.prose ol > li::marker { font: 600 0.9em var(--mono); }
.prose li > ul, .prose li > ol { margin: 6px 0 0; }

.prose li.task { list-style: none; margin-left: -1.4em; display: flex; gap: 10px; align-items: baseline; }
.prose li.task input { accent-color: var(--good); width: 16px; height: 16px; transform: translateY(2px); }

.prose :not(pre) > code {
    padding: 0.12em 0.4em;
    border-radius: 6px;
    background: rgba(122, 162, 247, 0.1);
    border: 1px solid rgba(122, 162, 247, 0.16);
    color: #c0d1ff;
    font: 0.86em var(--mono);
    word-break: break-word;
}

/* ---------- tables ---------- */

.table-wrap {
    margin: 0 0 16px;
    overflow-x: auto;
    border: 1px solid var(--border);
    border-radius: 10px;
}
.table-wrap table { width: 100%; border-collapse: collapse; font-size: 14.5px; }
.table-wrap th,
.table-wrap td { padding: 10px 14px; text-align: left; vertical-align: top; border-bottom: 1px solid var(--border); }
.table-wrap th { background: var(--surface-3); color: var(--text); font-weight: 600; white-space: nowrap; }
.table-wrap td { color: var(--text-soft); }
.table-wrap tr:last-child td { border-bottom: 0; }
.table-wrap tbody tr:hover td { background: rgba(122, 162, 247, 0.04); }

/* ---------- code ---------- */

.code {
    margin: 0 0 18px;
    border: 1px solid var(--border);
    border-radius: 12px;
    background: var(--code-bg);
    overflow: hidden;
}
.code figcaption {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 6px 8px 6px 14px;
    border-bottom: 1px solid var(--border);
    background: rgba(255, 255, 255, 0.02);
    color: var(--muted);
    font: 500 12px var(--mono);
    letter-spacing: 0.04em;
}
.code figcaption span::before {
    content: '';
    display: inline-block;
    width: 8px;
    height: 8px;
    margin-right: 38px;
    border-radius: 50%;
    background: var(--accent);
    box-shadow: 14px 0 0 var(--accent-2), 28px 0 0 var(--good);
    vertical-align: 1px;
}
.copy {
    padding: 4px 10px;
    border: 1px solid transparent;
    border-radius: 6px;
    background: transparent;
    color: var(--muted);
    font: 500 12px var(--font);
    cursor: pointer;
    transition: color .15s, border-color .15s, background .15s;
}
.copy:hover { color: var(--text); border-color: var(--border-strong); background: var(--surface-2); }
.copy.is-done { color: var(--good); }
.code pre {
    margin: 0;
    padding: 16px 18px;
    overflow-x: auto;
    font: 14px/1.6 var(--mono);
    tab-size: 4;
}
.code code { font: inherit; color: #d5dbe6; font-variant-ligatures: none; }

/* highlight.js tokens */
.hljs-keyword, .hljs-selector-tag, .hljs-built_in.hljs-keyword { color: #bb9af7; }
.hljs-built_in, .hljs-type, .hljs-class .hljs-title, .hljs-title.class_ { color: #2ac3de; }
.hljs-title, .hljs-title.function_, .hljs-function .hljs-title { color: #7aa2f7; }
.hljs-string, .hljs-regexp, .hljs-template-string { color: #9ece6a; }
.hljs-subst { color: #c0caf5; }
.hljs-number, .hljs-literal { color: #ff9e64; }
.hljs-comment, .hljs-quote { color: #6b7894; font-style: italic; }
.hljs-attr, .hljs-attribute, .hljs-property { color: #73daca; }
.hljs-variable, .hljs-template-variable, .hljs-params { color: #e0af68; }
.hljs-tag, .hljs-name { color: #f7768e; }
.hljs-operator, .hljs-punctuation { color: #89ddff; }
.hljs-meta { color: #7dcfff; }

/* ---------- diagrams ---------- */

.diagram {
    margin: 0 0 18px;
    padding: 20px;
    border: 1px solid var(--border);
    border-radius: 12px;
    background:
        radial-gradient(circle at 1px 1px, rgba(255, 255, 255, 0.05) 1px, transparent 0) 0 0 / 18px 18px,
        var(--code-bg);
    overflow-x: auto;
    text-align: center;
}
.diagram pre.mermaid {
    margin: 0;
    color: var(--muted);
    font: 13px/1.5 var(--mono);
    text-align: left;
    white-space: pre;
}
.diagram.is-ready pre.mermaid { text-align: center; white-space: normal; }
.diagram svg { max-width: 100%; height: auto; }

/* ---------- table of contents ---------- */

.toc > h2 { margin: 36px 0 16px; font-size: 24px; }
.toc__group { margin-bottom: 24px; }
.toc__group h3 {
    display: flex;
    align-items: center;
    gap: 12px;
    margin: 0 0 8px;
    font-size: 18px;
}
.toc__block {
    display: inline-grid;
    place-items: center;
    width: 30px;
    height: 30px;
    border-radius: 9px;
    background: var(--surface-3);
    border: 1px solid var(--border-strong);
    color: var(--accent-2);
    font: 600 14px var(--mono);
}
.toc__meta { margin-left: auto; color: var(--muted); font: 500 13px var(--mono); }
.toc__intro { margin: 0 0 10px 42px; color: var(--muted); font-size: 14px; }
.toc__list { margin: 0; padding: 0; list-style: none; }
.toc__item {
    display: flex;
    align-items: center;
    gap: 14px;
    margin: 0 0 8px 42px;
    padding: 12px 16px;
    border: 1px solid var(--border);
    border-radius: 12px;
    background: var(--surface);
    color: var(--text);
    transition: border-color .15s, background .15s, transform .15s;
}
.toc__item:hover {
    text-decoration: none;
    border-color: rgba(122, 162, 247, 0.5);
    background: var(--surface-2);
    transform: translateX(3px);
}
.toc__item .q-num { font-size: 13px; }
.toc__title { flex: 1; font-weight: 500; }
.toc__item .chips { flex-shrink: 0; }

/* ---------- side navigation ---------- */

.side-nav {
    position: fixed;
    top: 50%;
    z-index: 15;
    display: grid;
    place-items: center;
    width: 52px;
    height: 52px;
    margin-top: -26px;
    border: 1px solid var(--border-strong);
    border-radius: 50%;
    background: rgba(24, 32, 43, 0.85);
    backdrop-filter: blur(8px);
    -webkit-backdrop-filter: blur(8px);
    color: var(--text-soft);
    box-shadow: 0 8px 24px rgba(0, 0, 0, 0.35);
    transition: color .15s, border-color .15s, background .15s, transform .15s;
}
.side-nav.prev { left: max(16px, calc(50% - var(--content) / 2 - 110px)); }
.side-nav.next { right: max(16px, calc(50% - var(--content) / 2 - 110px)); }
.side-nav svg { width: 24px; height: 24px; fill: none; stroke: currentColor; stroke-width: 2.2; stroke-linecap: round; stroke-linejoin: round; }
.side-nav:hover {
    text-decoration: none;
    color: #fff;
    border-color: var(--accent);
    background: rgba(122, 162, 247, 0.18);
    transform: scale(1.06);
}
.side-nav.disabled { display: none; }

.side-nav__tip {
    position: absolute;
    top: 50%;
    width: max-content;
    max-width: 240px;
    padding: 8px 12px;
    border: 1px solid var(--border-strong);
    border-radius: 10px;
    background: var(--surface-3);
    color: var(--text);
    font-size: 13.5px;
    line-height: 1.4;
    text-align: left;
    opacity: 0;
    pointer-events: none;
    transform: translateY(-50%);
    transition: opacity .15s;
}
.side-nav__tip small { display: block; color: var(--muted); font-size: 11px; letter-spacing: 0.06em; text-transform: uppercase; }
.side-nav.prev .side-nav__tip { left: 64px; }
.side-nav.next .side-nav__tip { right: 64px; }
.side-nav:hover .side-nav__tip,
.side-nav:focus-visible .side-nav__tip { opacity: 1; }

/* ---------- bottom pager ---------- */

.pager { display: grid; grid-template-columns: 1fr 1fr; gap: 12px; margin-top: 32px; }
.pager__card {
    display: flex;
    flex-direction: column;
    gap: 2px;
    padding: 14px 18px;
    border: 1px solid var(--border);
    border-radius: 12px;
    background: var(--surface);
    color: var(--text);
    transition: border-color .15s, background .15s;
}
.pager__card small { color: var(--muted); font-size: 12px; }
.pager__card span { font-weight: 500; }
.pager__card.next { text-align: right; }
.pager__card:hover { text-decoration: none; border-color: rgba(122, 162, 247, 0.5); background: var(--surface-2); }
.pager__card.empty { border: 0; background: none; }

:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }

/* ---------- responsive ---------- */

@media (max-width: 1100px) {
    .side-nav {
        top: auto;
        bottom: 16px;
        margin-top: 0;
    }
    .side-nav.prev { left: 16px; }
    .side-nav.next { right: 16px; }
    .side-nav__tip { display: none; }
    .content { padding-bottom: 100px; }
}

@media (max-width: 640px) {
    .topbar__brand { font-size: 14px; }
    .content { padding-top: 24px; }
    .card { padding: 20px 18px; border-radius: 12px; }
    .toc__intro, .toc__item { margin-left: 0; }
    .toc__item { flex-wrap: wrap; gap: 8px 12px; }
    .toc__item .chips { width: 100%; }
    .code pre { font-size: 13px; padding: 14px; }
    .pager { grid-template-columns: 1fr; }
    .pager__card.empty { display: none; }
}

@media (prefers-reduced-motion: reduce) {
    * { transition: none !important; }
}

@media print {
    :root { color-scheme: light; }
    body { background: #fff; color: #000; }
    .topbar, .side-nav, .pager, .copy { display: none !important; }
    .card { box-shadow: none; background: #fff; border-color: #ccc; }
    .prose p, .prose ul, .prose ol, .table-wrap td { color: #222; }
}