:root {
  --bg: #f4f5f7;
  --surface: #ffffff;
  --surface-soft: #f8f9fb;
  --text: #101114;
  --muted: #676c75;
  --line: #e2e5ea;
  --dark: #111318;
  --accent: #1f2937;
  --radius: 22px;
  --shadow: 0 20px 60px rgba(17, 19, 24, .08);
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  font-family: Inter, "Segoe UI", Arial, sans-serif;
  color: var(--text);
  background: var(--bg);
  line-height: 1.72;
}

a {
  color: inherit;
}

img {
  max-width: 100%;
}

.hero {
  min-height: 78vh;
  display: flex;
  align-items: center;
  position: relative;
  overflow: hidden;
  background:
    radial-gradient(circle at 85% 15%, rgba(255, 255, 255, .13), transparent 32%),
    linear-gradient(145deg, #0a0b0e 0%, #161920 70%, #0a0b0e 100%);
  color: #fff;
  padding: 88px 24px;
}

.hero::after {
  content: "";
  position: absolute;
  inset: auto -12% -46% 38%;
  width: 760px;
  height: 760px;
  border: 1px solid rgba(255, 255, 255, .08);
  border-radius: 50%;
  box-shadow: 0 0 0 70px rgba(255, 255, 255, .025), 0 0 0 140px rgba(255, 255, 255, .018);
}

.hero-inner {
  width: min(1180px, 100%);
  margin: 0 auto;
  position: relative;
  z-index: 1;
}

.eyebrow {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  padding: 8px 13px;
  border: 1px solid rgba(255, 255, 255, .16);
  border-radius: 999px;
  color: rgba(255, 255, 255, .76);
  font-size: .78rem;
  font-weight: 700;
  letter-spacing: .12em;
  text-transform: uppercase;
}

.eyebrow::before {
  content: "";
  width: 7px;
  height: 7px;
  background: #fff;
  border-radius: 50%;
}

h1 {
  max-width: 880px;
  margin: 28px 0 22px;
  font-size: clamp(3rem, 7vw, 6.5rem);
  line-height: .98;
  letter-spacing: -.055em;
  font-weight: 750;
}

.hero-subtitle {
  max-width: 760px;
  margin: 0;
  color: rgba(255, 255, 255, .72);
  font-size: clamp(1.08rem, 2vw, 1.35rem);
}

.hero-meta {
  display: flex;
  flex-wrap: wrap;
  gap: 14px;
  margin-top: 38px;
}

.hero-meta span {
  padding: 10px 14px;
  background: rgba(255, 255, 255, .08);
  border: 1px solid rgba(255, 255, 255, .1);
  border-radius: 12px;
  color: rgba(255, 255, 255, .78);
  font-size: .92rem;
}

.layout {
  width: min(1240px, calc(100% - 40px));
  margin: -70px auto 80px;
  position: relative;
  z-index: 2;
  display: grid;
  grid-template-columns: 310px minmax(0, 1fr);
  gap: 28px;
  align-items: start;
}

.toc {
  position: sticky;
  top: 18px;
  max-height: calc(100vh - 36px);
  overflow: auto;
  background: rgba(255, 255, 255, .94);
  backdrop-filter: blur(14px);
  border: 1px solid rgba(255, 255, 255, .9);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 24px;
}

.toc h2 {
  margin: 0 0 16px;
  font-size: 1.05rem;
  letter-spacing: -.02em;
}

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

.toc li+li {
  border-top: 1px solid var(--line);
}

.toc a {
  display: grid;
  grid-template-columns: 36px 1fr;
  gap: 8px;
  align-items: center;
  padding: 10px 0;
  text-decoration: none;
  color: #30343b;
  font-size: .88rem;
  line-height: 1.35;
}

.toc a:hover {
  color: #000;
}

.toc a span {
  color: #9aa0aa;
  font-variant-numeric: tabular-nums;
  font-size: .76rem;
  font-weight: 700;
}

.content {
  min-width: 0;
}

.intro-card {
  background: var(--surface);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: clamp(28px, 5vw, 56px);
  margin-bottom: 28px;
}

.intro-card h2 {
  margin-top: 0;
  font-size: clamp(1.65rem, 3vw, 2.5rem);
  letter-spacing: -.04em;
}

.intro-card p {
  color: var(--muted);
  max-width: 760px;
}

.manual-section {
  display: grid;
  grid-template-columns: 84px minmax(0, 1fr);
  gap: 24px;
  background: var(--surface);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: clamp(28px, 4vw, 48px);
  margin-bottom: 24px;
  scroll-margin-top: 22px;
}

.section-number {
  width: 62px;
  height: 62px;
  display: grid;
  place-items: center;
  border-radius: 18px;
  background: var(--dark);
  color: #fff;
  font-size: .92rem;
  font-weight: 800;
  letter-spacing: .08em;
}

.section-body h2 {
  margin: 0 0 18px;
  font-size: clamp(1.55rem, 3vw, 2.25rem);
  line-height: 1.15;
  letter-spacing: -.04em;
}

.section-body h3 {
  margin: 28px 0 6px;
  font-size: 1.02rem;
}

.section-body p {
  margin: 0 0 16px;
  color: #3f444c;
}

.content-list {
  margin: 14px 0 22px;
  padding-left: 1.3rem;
  color: #3f444c;
}

.content-list li {
  margin: 8px 0;
  padding-left: 5px;
}

.screenshot-placeholder {
  min-height: 280px;
  margin: 28px 0 10px;
  border: 2px dashed #cbd0d8;
  border-radius: 18px;
  background:
    linear-gradient(135deg, rgba(0, 0, 0, .018) 25%, transparent 25%) -12px 0/24px 24px,
    linear-gradient(225deg, rgba(0, 0, 0, .018) 25%, transparent 25%) -12px 0/24px 24px,
    linear-gradient(315deg, rgba(0, 0, 0, .018) 25%, transparent 25%) 0 0/24px 24px,
    linear-gradient(45deg, rgba(0, 0, 0, .018) 25%, #fafbfc 25%) 0 0/24px 24px;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  text-align: center;
  color: #707680;
  padding: 24px;
}

.placeholder-icon {
  width: 54px;
  height: 54px;
  display: grid;
  place-items: center;
  border: 1px solid #cbd0d8;
  border-radius: 15px;
  background: #fff;
  color: #111;
  font-size: 1.8rem;
  margin-bottom: 12px;
}

.screenshot-placeholder strong {
  color: #20242a;
}

.screenshot-placeholder span {
  font-size: .88rem;
}

.image-caption {
  color: #8a9099 !important;
  font-size: .88rem;
  text-align: center;
  font-style: italic;
}

.back-to-top {
  display: inline-block;
  margin-top: 12px;
  color: #6a7079;
  font-size: .82rem;
  text-decoration: none;
}

footer {
  padding: 48px 24px 70px;
  text-align: center;
  color: #777d87;
  font-size: .9rem;
}

@media (max-width: 980px) {
  .layout {
    grid-template-columns: 1fr;
    margin-top: -45px;
  }

  .toc {
    position: static;
    max-height: none;
  }

  .toc ol {
    columns: 2;
    column-gap: 26px;
  }

  .toc li {
    break-inside: avoid;
  }
}

@media (max-width: 680px) {
  .hero {
    min-height: auto;
    padding: 64px 20px 110px;
  }

  .layout {
    width: min(100% - 24px, 1240px);
  }

  .toc ol {
    columns: 1;
  }

  .manual-section {
    grid-template-columns: 1fr;
    padding: 24px 20px;
  }

  .section-number {
    width: 48px;
    height: 48px;
    border-radius: 14px;
  }

  .screenshot-placeholder {
    min-height: 210px;
  }
}

@media print {
  body {
    background: #fff;
  }

  .hero {
    min-height: auto;
    color: #000;
    background: #fff;
    padding: 30px 0 40px;
  }

  .hero::after,
  .toc,
  .back-to-top {
    display: none !important;
  }

  .hero-subtitle,
  .hero-meta span {
    color: #333;
  }

  .hero-meta span {
    border: 1px solid #ddd;
    background: #fff;
  }

  .layout {
    display: block;
    width: 100%;
    margin: 0;
  }

  .intro-card,
  .manual-section {
    box-shadow: none;
    border: 1px solid #ddd;
    break-inside: avoid;
  }
}