:root {
  color-scheme: light;
  --bg: #f7f9fc;
  --surface: #ffffff;
  --surface-2: #eef3f9;
  --surface-3: #e5ebf4;
  --text: #172033;
  --muted: #5f6d82;
  --line: #dce3ed;
  --brand: #3157d5;
  --brand-2: #18a7b5;
  --brand-soft: #eaf0ff;
  --green: #16805d;
  --green-soft: #e7f7f1;
  --violet: #7048c8;
  --violet-soft: #f0eafe;
  --orange: #b35b0d;
  --red: #b33131;
  --shadow: 0 18px 45px rgba(31, 48, 82, .09);
  --shadow-sm: 0 8px 24px rgba(31, 48, 82, .08);
  --shadow-lg: 0 30px 80px rgba(22, 39, 76, .18);
  --radius: 22px;
  --radius-sm: 14px;
  --container: 1180px;
  --ease-out: cubic-bezier(.2, .8, .2, 1);
}

:root[data-theme="dark"] {
  color-scheme: dark;
  --bg: #0c1220;
  --surface: #121b2c;
  --surface-2: #172235;
  --surface-3: #223047;
  --text: #edf3ff;
  --muted: #a9b6ca;
  --line: #2b3950;
  --brand: #7f9cff;
  --brand-2: #5ad5dc;
  --brand-soft: #1e2a50;
  --green: #64d2a8;
  --green-soft: #15372f;
  --violet: #bb9cf7;
  --violet-soft: #2f2451;
  --orange: #f0a757;
  --red: #ff8585;
  --shadow: 0 18px 45px rgba(0, 0, 0, .22);
  --shadow-sm: 0 8px 24px rgba(0, 0, 0, .18);
  --shadow-lg: 0 30px 80px rgba(0, 0, 0, .38);
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; scroll-padding-top: 96px; }
body { margin: 0; overflow-x: hidden; font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif; background: var(--bg); color: var(--text); line-height: 1.65; }
::selection { background: color-mix(in srgb, var(--brand) 24%, transparent); }
img { max-width: 100%; height: auto; }
a { color: var(--brand); }
button, input, select { font: inherit; }
button { color: inherit; }
:where(a, button, input, select):focus-visible { outline: 3px solid color-mix(in srgb, var(--brand) 55%, white); outline-offset: 3px; }
.container { width: min(calc(100% - 40px), var(--container)); margin-inline: auto; }
.sr-only { position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px; overflow: hidden; clip: rect(0, 0, 0, 0); white-space: nowrap; border: 0; }
.skip-link { position: fixed; left: 16px; top: 12px; z-index: 1000; background: var(--text); color: var(--bg); padding: 10px 14px; border-radius: 9px; transform: translateY(-160%); transition: transform .2s; }
.skip-link:focus { transform: translateY(0); }

.site-header { position: sticky; top: 0; z-index: 50; background: color-mix(in srgb, var(--bg) 86%, transparent); backdrop-filter: blur(16px); border-bottom: 1px solid color-mix(in srgb, var(--line) 78%, transparent); transition: box-shadow .3s var(--ease-out), background .3s; }
.site-header.scrolled { background: color-mix(in srgb, var(--bg) 94%, transparent); box-shadow: 0 8px 30px rgba(18, 33, 64, .08); }
.nav-wrap { min-height: 88px; display: flex; align-items: center; gap: 24px; }
.brand { display: inline-flex; align-items: center; gap: 11px; color: var(--text); text-decoration: none; flex-shrink: 0; }
.brand img { width: 56px; height: 56px; object-fit: cover; border: 1px solid color-mix(in srgb, var(--brand) 34%, var(--line)); border-radius: 16px; box-shadow: 0 8px 24px rgba(49, 87, 213, .22), inset 0 0 0 1px rgba(255, 255, 255, .07); transition: transform .35s var(--ease-out), box-shadow .35s, filter .35s; }
.brand:hover img { transform: translateY(-1px) rotate(-3deg) scale(1.055); box-shadow: 0 13px 30px rgba(49, 87, 213, .32), 0 0 20px color-mix(in srgb, var(--brand-2) 18%, transparent); filter: saturate(1.08); }
.brand span { display: grid; line-height: 1.08; }
.brand strong { font-size: 1.08rem; letter-spacing: -.02em; }
.brand small { color: var(--muted); margin-top: 4px; font-size: .72rem; letter-spacing: .06em; text-transform: uppercase; }
.main-nav { margin-left: auto; display: flex; align-items: center; gap: 4px; }
.main-nav a { color: var(--muted); text-decoration: none; font-weight: 700; font-size: .92rem; padding: 10px 13px; border-radius: 10px; transition: color .2s, background .2s, transform .2s var(--ease-out); }
.main-nav a:hover { transform: translateY(-1px); }
.main-nav a:hover, .main-nav a.active { background: var(--surface-2); color: var(--text); }
.main-nav .nav-quiz { background: var(--brand); color: white; margin-left: 4px; }
.main-nav .nav-quiz:hover, .main-nav .nav-quiz.active { background: color-mix(in srgb, var(--brand) 86%, black); color: white; }
.theme-toggle, .nav-toggle { width: 42px; height: 42px; border: 1px solid var(--line); background: var(--surface); border-radius: 12px; cursor: pointer; display: grid; place-items: center; transition: transform .22s var(--ease-out), border-color .22s, box-shadow .22s; }
.theme-toggle:hover, .nav-toggle:hover { border-color: var(--brand); transform: translateY(-2px) rotate(3deg); box-shadow: var(--shadow-sm); }
.nav-toggle { display: none; }
.reading-progress { position: fixed; inset: 0 0 auto; height: 3px; z-index: 100; pointer-events: none; background: transparent; }
.reading-progress span { display: block; width: 0; height: 100%; background: linear-gradient(90deg, var(--brand-2), var(--brand), var(--violet)); box-shadow: 0 0 10px color-mix(in srgb, var(--brand) 55%, transparent); }

.hero { position: relative; overflow: hidden; padding: 92px 0 86px; background: radial-gradient(circle at 75% 30%, color-mix(in srgb, var(--brand-2) 17%, transparent), transparent 34%), radial-gradient(circle at 18% 15%, color-mix(in srgb, var(--brand) 14%, transparent), transparent 30%); }
.hero::after { content: ""; position: absolute; inset: auto -8% -200px; height: 310px; background: var(--surface); border-radius: 50% 50% 0 0 / 22% 22% 0 0; opacity: .55; pointer-events: none; }
.hero-grid { display: grid; grid-template-columns: 1.1fr .9fr; gap: 70px; align-items: center; position: relative; z-index: 1; }
.eyebrow { margin: 0 0 12px; color: var(--brand); font-weight: 800; text-transform: uppercase; letter-spacing: .11em; font-size: .78rem; }
h1, h2, h3 { line-height: 1.15; margin-top: 0; letter-spacing: -.028em; }
h1 { font-size: clamp(2.65rem, 5vw, 5.2rem); margin-bottom: 22px; }
h2 { font-size: clamp(2rem, 3.3vw, 3.35rem); margin-bottom: 18px; }
h3 { font-size: 1.2rem; }
.lead { font-size: clamp(1.08rem, 1.7vw, 1.27rem); color: var(--muted); max-width: 720px; }
.button-row { display: flex; flex-wrap: wrap; gap: 12px; margin-top: 30px; }
.button-row.centered { justify-content: center; }
.button { position: relative; isolation: isolate; overflow: hidden; display: inline-flex; align-items: center; justify-content: center; min-height: 48px; padding: 12px 20px; border-radius: 12px; border: 1px solid transparent; text-decoration: none; font-weight: 800; cursor: pointer; transition: transform .25s var(--ease-out), box-shadow .25s, background .25s, border-color .25s; }
.button::before { content: ""; position: absolute; inset: -2px; z-index: 0; pointer-events: none; background: linear-gradient(110deg, transparent 25%, rgba(255,255,255,.32) 45%, transparent 65%); transform: translateX(-120%); transition: transform .65s var(--ease-out); }
.button:hover { transform: translateY(-3px) scale(1.015); }
.button:hover::before { transform: translateX(120%); }
.button.primary { background: var(--brand); color: white; box-shadow: 0 10px 24px color-mix(in srgb, var(--brand) 25%, transparent); }
.button.primary:hover { box-shadow: 0 16px 34px color-mix(in srgb, var(--brand) 34%, transparent); }
.button.secondary { background: var(--surface); color: var(--text); border-color: var(--line); }
.button.secondary:hover { border-color: color-mix(in srgb, var(--brand) 50%, var(--line)); box-shadow: var(--shadow-sm); }
.button.large { min-width: 220px; min-height: 54px; }
.hero-facts { display: flex; gap: 24px; list-style: none; padding: 0; margin: 40px 0 0; }
.hero-facts li { display: grid; border-left: 2px solid var(--line); padding-left: 14px; }
.hero-facts strong { font-size: 1.45rem; }
.hero-facts span { color: var(--muted); font-size: .82rem; }
.hero-photo { position: relative; margin: 0; }
.hero-photo-frame { min-height: 500px; aspect-ratio: 4 / 5; position: relative; border-radius: 34px; background: #0d1730; box-shadow: var(--shadow-lg); transform: rotate(.7deg); }
.hero-photo-frame::before { content: ""; position: absolute; inset: 12px -12px -12px 12px; z-index: -1; border-radius: inherit; border: 1px solid color-mix(in srgb, var(--brand) 28%, var(--line)); }
.hero-photo-frame img { width: 100%; height: 100%; display: block; object-fit: cover; object-position: 61% center; border-radius: inherit; filter: saturate(.92) contrast(1.03); transition: transform .8s var(--ease-out), filter .5s; }
.hero-photo:hover .hero-photo-frame img { transform: scale(1.025); filter: saturate(1) contrast(1.04); }
.photo-glow { position: absolute; inset: 0; border-radius: inherit; background: linear-gradient(180deg, transparent 56%, rgba(7, 17, 38, .72)), linear-gradient(90deg, rgba(14, 29, 66, .22), transparent 45%); pointer-events: none; }
.hero-topic-links { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 10px; margin-top: 20px; }
.visual-card { min-width: 0; background: var(--surface); border: 1px solid var(--line); border-radius: 14px; padding: 12px 10px; color: var(--text); font-size: .86rem; font-weight: 800; text-decoration: none; display: flex; align-items: center; justify-content: center; gap: 7px; transition: color .2s, background .2s, border-color .2s, transform .22s var(--ease-out), box-shadow .22s var(--ease-out); }
.visual-card:hover { color: var(--brand); background: var(--brand-soft); border-color: color-mix(in srgb, var(--brand) 42%, var(--line)); transform: translateY(-2px); box-shadow: var(--shadow-sm); }
.visual-card span { font-size: 1.3rem; }

.section { padding: 88px 0; }
.section-muted { background: var(--surface-2); }
.section-heading { max-width: 760px; margin-bottom: 38px; }
.section-heading > p:last-child { color: var(--muted); font-size: 1.06rem; }
.section-heading.compact { max-width: none; }
.feature-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 22px; }
.feature-card { position: relative; overflow: hidden; min-height: 330px; display: flex; flex-direction: column; padding: 28px; background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius); color: var(--text); text-decoration: none; box-shadow: var(--shadow-sm); transition: transform .32s var(--ease-out), box-shadow .32s, border-color .32s; }
.feature-card::before { content: ""; position: absolute; width: 160px; height: 160px; border-radius: 50%; right: -70px; top: -75px; background: var(--card-soft); }
.feature-card::after { content: ""; position: absolute; inset: 0; background: linear-gradient(120deg, transparent 30%, color-mix(in srgb, var(--card-accent) 8%, transparent), transparent 70%); transform: translateX(-100%); transition: transform .7s var(--ease-out); pointer-events: none; }
.feature-card:hover { transform: translateY(-9px); box-shadow: var(--shadow-lg); border-color: var(--card-accent); }
.feature-card:hover::after { transform: translateX(100%); }
.accent-blue { --card-accent: var(--brand); --card-soft: var(--brand-soft); }.accent-green { --card-accent: var(--green); --card-soft: var(--green-soft); }.accent-violet { --card-accent: var(--violet); --card-soft: var(--violet-soft); }
.feature-icon { width: 58px; height: 58px; border-radius: 16px; display: grid; place-items: center; font-size: 1.75rem; background: var(--card-soft); margin-bottom: 34px; transition: transform .35s var(--ease-out); }
.feature-card:hover .feature-icon { transform: rotate(-6deg) scale(1.1); }
.card-kicker { color: var(--card-accent); font-weight: 800; text-transform: uppercase; font-size: .72rem; letter-spacing: .08em; margin: 0 0 8px; }
.feature-card h3 { font-size: 1.55rem; margin-bottom: 12px; }
.feature-card p:not(.card-kicker) { color: var(--muted); }
.card-link { margin-top: auto; font-weight: 800; color: var(--card-accent); transition: transform .3s var(--ease-out); }
.feature-card:hover .card-link { transform: translateX(6px); }
.split-grid { display: grid; grid-template-columns: 1.25fr .75fr; gap: 60px; align-items: center; }
.steps { list-style: none; margin: 34px 0 0; padding: 0; display: grid; gap: 24px; }
.steps li { display: grid; grid-template-columns: 58px 1fr; gap: 18px; align-items: start; }
.steps li > span { width: 50px; height: 50px; display: grid; place-items: center; border-radius: 14px; background: var(--surface); color: var(--brand); font-weight: 900; box-shadow: var(--shadow-sm); }
.steps strong { font-size: 1.05rem; }
.steps p { margin: 4px 0 0; color: var(--muted); }
.callout { background: linear-gradient(145deg, var(--brand), #183eaa); color: white; padding: 34px; border-radius: var(--radius); box-shadow: 0 24px 55px rgba(49, 87, 213, .24); }
.callout-icon { font-size: 2rem; }.callout h3 { font-size: 1.7rem; margin: 18px 0 12px; }.callout p { color: rgba(255,255,255,.84); }.callout a { color: white; font-weight: 800; }
.search-field { max-width: 670px; display: flex; gap: 10px; align-items: center; background: var(--surface); border: 1px solid var(--line); border-radius: 15px; padding: 0 16px; box-shadow: var(--shadow-sm); margin-bottom: 26px; }
.search-field input { width: 100%; height: 54px; border: 0; outline: 0; background: transparent; color: var(--text); }
.glossary-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 18px; }
.glossary-card { background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius-sm); padding: 22px; transition: transform .28s var(--ease-out), border-color .28s, box-shadow .28s; }
.glossary-card:hover { transform: translateY(-4px); border-color: color-mix(in srgb, var(--brand) 42%, var(--line)); box-shadow: var(--shadow-sm); }
.glossary-card h3 { margin-bottom: 8px; }.glossary-card p { margin: 0; color: var(--muted); font-size: .93rem; }
.empty-state { color: var(--muted); }

.page-hero { padding: 74px 0; border-bottom: 1px solid var(--line); background: radial-gradient(circle at 85% 20%, var(--hero-soft), transparent 30%), linear-gradient(180deg, var(--surface), var(--bg)); }
.hero-network { --hero-soft: color-mix(in srgb, var(--brand-2) 18%, transparent); }.hero-security { --hero-soft: color-mix(in srgb, var(--green) 18%, transparent); }.hero-media { --hero-soft: color-mix(in srgb, var(--violet) 18%, transparent); }
.page-hero-grid { display: grid; grid-template-columns: 1fr auto; gap: 40px; align-items: center; }
.page-hero h1 { font-size: clamp(2.45rem, 5vw, 4.7rem); max-width: 920px; }
.breadcrumbs { display: flex; align-items: center; gap: 9px; color: var(--muted); font-size: .88rem; margin: 0 0 26px; }.breadcrumbs a { color: var(--muted); }
.chapter-badge { width: 160px; height: 180px; background: var(--surface); border: 1px solid var(--line); border-radius: 32px; box-shadow: var(--shadow); display: grid; place-items: center; align-content: center; }
.chapter-badge span { font-size: 2.6rem; }.chapter-badge strong { font-size: 2.7rem; line-height: 1; margin: 6px 0; }.chapter-badge small { color: var(--muted); text-transform: uppercase; letter-spacing: .12em; font-weight: 800; }
.chapter-layout { display: grid; grid-template-columns: 230px minmax(0, 1fr); gap: 64px; padding-top: 70px; padding-bottom: 90px; }
.toc { position: sticky; top: 108px; align-self: start; display: grid; gap: 3px; border-left: 1px solid var(--line); padding-left: 18px; }
.toc strong { margin-bottom: 10px; font-size: .82rem; text-transform: uppercase; letter-spacing: .08em; }
.toc a { color: var(--muted); text-decoration: none; padding: 7px 8px; border-radius: 8px; font-size: .9rem; transition: color .2s, background .2s, transform .2s var(--ease-out); }.toc a:hover, .toc a.active { color: var(--brand); background: var(--surface-2); transform: translateX(3px); }.toc a.active { font-weight: 800; box-shadow: inset 3px 0 0 var(--brand); }
.chapter-content { min-width: 0; }
.content-section { margin-bottom: 88px; }
.content-section > p:not(.section-number), .content-section > .lead { color: var(--muted); font-size: 1.03rem; }
.content-section h2 { font-size: clamp(1.85rem, 3vw, 3rem); }
.section-number { color: var(--brand); text-transform: uppercase; letter-spacing: .1em; font-size: .75rem; font-weight: 900; margin: 0 0 10px; }
.subheading { margin-top: 34px; }
.info-grid { display: grid; gap: 16px; margin-top: 28px; }.info-grid.three { grid-template-columns: repeat(3, 1fr); }
.info-card { background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius-sm); padding: 22px; transition: transform .28s var(--ease-out), box-shadow .28s, border-color .28s; }.info-card:hover { transform: translateY(-4px); box-shadow: var(--shadow-sm); border-color: color-mix(in srgb, var(--brand) 35%, var(--line)); }.info-card > span { font-size: 1.7rem; }.info-card h3 { margin: 16px 0 8px; }.info-card p { margin: 0; color: var(--muted); font-size: .92rem; }
.definition, .note, .warning { margin-top: 28px; border-radius: var(--radius-sm); padding: 20px 22px; }
.definition { background: var(--brand-soft); border-left: 4px solid var(--brand); }.note { background: var(--surface-2); border: 1px solid var(--line); }.warning { background: color-mix(in srgb, #f5a623 11%, var(--surface)); border: 1px solid color-mix(in srgb, #f5a623 35%, var(--line)); }
.definition p, .note p, .warning p { margin: 6px 0 0; color: var(--muted); }
.comparison-table-wrap { overflow-x: auto; margin-top: 28px; border: 1px solid var(--line); border-radius: var(--radius-sm); }
.comparison-table { width: 100%; border-collapse: collapse; background: var(--surface); min-width: 720px; }
.comparison-table th, .comparison-table td { padding: 17px; border-bottom: 1px solid var(--line); text-align: left; vertical-align: top; }.comparison-table th { background: var(--surface-2); font-size: .78rem; text-transform: uppercase; letter-spacing: .05em; }.comparison-table tr:last-child td { border-bottom: 0; }.comparison-table td { color: var(--muted); }.comparison-table td strong { color: var(--text); display: block; }.comparison-table td small { display: block; margin-top: 3px; }
.material-list { display: grid; gap: 12px; margin-top: 28px; }.material-list article { display: grid; grid-template-columns: 82px 1fr; gap: 18px; padding: 18px; background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius-sm); }.material-list h3 { margin-bottom: 6px; }.material-list p { margin: 0; color: var(--muted); }
.level { align-self: start; text-align: center; padding: 6px 8px; border-radius: 999px; font-weight: 900; text-transform: uppercase; font-size: .68rem; }.level-low { background: var(--green-soft); color: var(--green); }.level-mid { background: color-mix(in srgb, #f6b73c 18%, var(--surface)); color: var(--orange); }.level-high { background: color-mix(in srgb, #e35656 14%, var(--surface)); color: var(--red); }

.simulator-card { background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius); padding: 30px; box-shadow: var(--shadow); }
.sim-header { display: flex; justify-content: space-between; gap: 20px; align-items: start; margin-bottom: 26px; }.sim-header h2 { margin-bottom: 8px; }.sim-header p:last-child { color: var(--muted); margin-bottom: 0; }.sim-label { background: var(--green-soft); color: var(--green); padding: 7px 11px; border-radius: 999px; font-size: .72rem; font-weight: 900; white-space: nowrap; }
.sim-grid { display: grid; grid-template-columns: 350px 1fr; gap: 28px; }.sim-controls-panel { background: var(--surface-2); border-radius: var(--radius-sm); padding: 20px; display: grid; gap: 18px; }.sim-controls-panel label, .range-grid label { display: grid; gap: 8px; font-weight: 800; font-size: .9rem; }.sim-controls-panel select, .range-grid select { width: 100%; border: 1px solid var(--line); background: var(--surface); color: var(--text); border-radius: 10px; padding: 10px 12px; }.sim-controls-panel input[type="range"], .range-grid input[type="range"] { width: 100%; accent-color: var(--brand); }.sim-controls-panel output, .range-grid output { color: var(--brand); font-weight: 900; }
.sim-result-list { display: grid; border-top: 1px solid var(--line); padding-top: 12px; }.sim-result-list div { display: flex; justify-content: space-between; gap: 12px; padding: 9px 0; }.sim-result-list span { color: var(--muted); }.quality { padding: 2px 8px; border-radius: 999px; font-size: .8rem; }.quality.excellent, .quality.good { color: var(--green); background: var(--green-soft); }.quality.fair { color: var(--orange); background: color-mix(in srgb, #f6b73c 16%, var(--surface)); }.quality.bad { color: var(--red); background: color-mix(in srgb, #e35656 14%, var(--surface)); }
.signal-stage { min-height: 350px; position: relative; border-radius: var(--radius-sm); overflow: hidden; background: linear-gradient(180deg, #d9ebf8 0 62%, #c9dec7 62%); display: flex; align-items: center; justify-content: space-between; padding: 48px; }
:root[data-theme="dark"] .signal-stage { background: linear-gradient(180deg, #182c43 0 62%, #1d372e 62%); }
.router-node, .device-node { position: relative; z-index: 3; display: grid; place-items: center; gap: 4px; }.router-node span, .device-node span { font-size: 3rem; }.router-node small, .device-node small { background: rgba(255,255,255,.82); color: #172033; padding: 3px 8px; border-radius: 999px; font-weight: 800; }
.wave-lines { position: absolute; left: 82px; top: 50%; width: 48%; height: 170px; transform: translateY(-50%); }.wave-lines i { position: absolute; left: 0; top: 50%; border: 3px solid rgba(49,87,213,.35); border-left: 0; border-top-color: transparent; border-bottom-color: transparent; border-radius: 50%; transform: translateY(-50%); animation: pulse-wave 2.3s infinite; }.wave-lines i:nth-child(1){width:60px;height:70px}.wave-lines i:nth-child(2){width:110px;height:110px;animation-delay:.25s}.wave-lines i:nth-child(3){width:170px;height:145px;animation-delay:.5s}.wave-lines i:nth-child(4){width:240px;height:175px;animation-delay:.75s}
@keyframes pulse-wave { 50% { opacity: .35; } }
.wall { width: 58px; height: 240px; position: absolute; left: 53%; top: 50%; transform: translate(-50%,-50%); z-index: 2; border-radius: 5px; display: grid; place-items: center; box-shadow: 0 10px 22px rgba(0,0,0,.14); }.wall span { transform: rotate(-90deg); color: white; font-size: .7rem; text-transform: uppercase; letter-spacing: .12em; font-weight: 900; }.wall-none { opacity: 0; }.wall-wood { background: repeating-linear-gradient(90deg,#a56b3b 0 10px,#bd8350 10px 20px); }.wall-brick { background: repeating-linear-gradient(0deg,#b95c45 0 17px,#e7b1a3 17px 20px); }.wall-concrete { background: #777f89; }.wall-water { background: rgba(38,151,205,.75); }.wall-metal { background: linear-gradient(90deg,#6d7783,#c3ccd3,#646e78); }
.signal-meter { position: absolute; right: 46px; top: 38px; display: flex; align-items: end; gap: 4px; height: 42px; }.signal-meter b { width: 7px; background: var(--green); border-radius: 3px 3px 0 0; transition: opacity .2s, background .2s; }.signal-meter b:nth-child(1){height:10px}.signal-meter b:nth-child(2){height:20px}.signal-meter b:nth-child(3){height:30px}.signal-meter b:nth-child(4){height:40px}
.checklist { display: grid; gap: 14px; margin-top: 28px; }.checklist article { display: grid; grid-template-columns: 48px 1fr; gap: 17px; padding: 18px; background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius-sm); }.checklist article > span { width: 42px; height: 42px; display: grid; place-items: center; background: var(--brand-soft); color: var(--brand); border-radius: 12px; font-weight: 900; }.checklist h3 { margin-bottom: 5px; }.checklist p { color: var(--muted); margin: 0; }
.versus-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 20px; margin-top: 28px; }.versus-card { padding: 28px; border-radius: var(--radius); border: 1px solid var(--line); background: var(--surface); }.versus-card.copper { border-top: 5px solid #b56f2b; }.versus-card.fiber { border-top: 5px solid var(--brand-2); }.versus-icon { font-size: 2rem; }.versus-card ul { color: var(--muted); padding-left: 20px; }.versus-card li { margin: 8px 0; }
.range-grid { display: grid; grid-template-columns: 1fr 1fr 1fr; gap: 18px; padding: 20px; border-radius: var(--radius-sm); background: var(--surface-2); }.result-compare { display: grid; grid-template-columns: 1fr 1fr; gap: 18px; margin-top: 20px; }.result-compare article { border: 1px solid var(--line); border-radius: var(--radius-sm); padding: 22px; }.result-title { display: flex; gap: 10px; align-items: center; }.result-title span { font-size: 1.5rem; }.result-title h3 { margin: 0; }.result-compare dl { margin: 18px 0 0; }.result-compare dl div { display: flex; justify-content: space-between; gap: 15px; padding: 10px 0; border-top: 1px solid var(--line); }.result-compare dt { color: var(--muted); }.result-compare dd { margin: 0; font-weight: 900; text-align: right; }
.threat-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 16px; margin-top: 28px; }.threat-grid article { padding: 22px; background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius-sm); }.threat-grid article > span { font-size: 1.7rem; }.threat-grid h3 { margin: 13px 0 7px; }.threat-grid p { color: var(--muted); margin: 0; font-size: .92rem; }
.inspection-card { display: grid; grid-template-columns: .9fr 1.1fr; gap: 28px; margin-top: 28px; }.fake-mail { background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius); padding: 24px; box-shadow: var(--shadow-sm); }.mail-head { display: flex; gap: 12px; align-items: center; border-bottom: 1px solid var(--line); padding-bottom: 16px; margin-bottom: 18px; }.avatar { width: 40px; height: 40px; display: grid; place-items: center; border-radius: 50%; background: #0a66c2; color: white; font-weight: 900; }.mail-head div { display: grid; }.mail-head small { color: var(--muted); }.fake-mail button { border: 0; background: #0a66c2; color: white; padding: 11px 16px; border-radius: 8px; font-weight: 800; }.inspection-points { display: grid; gap: 12px; }.inspection-points article { display: grid; grid-template-columns: 34px 1fr; gap: 12px; }.inspection-points b { width: 32px; height: 32px; display: grid; place-items: center; border-radius: 9px; background: color-mix(in srgb, #e35656 14%, var(--surface)); color: var(--red); }.inspection-points h3 { margin-bottom: 4px; }.inspection-points p { margin: 0; color: var(--muted); }
.backup-visual { display: grid; grid-template-columns: 1fr auto 1fr auto 1fr; gap: 18px; align-items: center; margin: 30px 0; }.backup-visual div { min-height: 150px; display: grid; place-items: center; align-content: center; background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius); text-align: center; padding: 20px; }.backup-visual strong { font-size: 3rem; color: var(--brand); }.backup-visual span { color: var(--muted); }.backup-visual i { color: var(--brand); font-style: normal; font-size: 1.6rem; }
.principle-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 16px; margin-top: 26px; }.principle-grid article { padding: 20px; border-left: 4px solid var(--green); background: var(--surface); border-radius: 0 var(--radius-sm) var(--radius-sm) 0; }.principle-grid h3 { margin-bottom: 7px; }.principle-grid p { margin: 0; color: var(--muted); }.rights-row { display: flex; flex-wrap: wrap; gap: 9px; }.rights-row span { background: var(--green-soft); color: var(--green); border-radius: 999px; padding: 8px 13px; font-weight: 800; font-size: .86rem; }
.timeline { display: grid; gap: 18px; margin-top: 28px; position: relative; }.timeline::before { content: ""; position: absolute; left: 23px; top: 12px; bottom: 12px; width: 2px; background: var(--line); }.timeline article { display: grid; grid-template-columns: 48px 1fr; gap: 18px; position: relative; }.timeline article > span { width: 48px; height: 48px; display: grid; place-items: center; border-radius: 50%; background: var(--brand); color: white; font-weight: 900; z-index: 1; }.timeline h3 { margin: 3px 0 5px; }.timeline p { color: var(--muted); margin: 0; }
.flow { display: grid; grid-template-columns: 1fr auto 1fr auto 1fr; gap: 15px; align-items: center; margin: 28px 0; }.flow div { background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius-sm); padding: 20px; text-align: center; display: grid; }.flow span { width: 34px; height: 34px; display: grid; place-items: center; margin: 0 auto 9px; background: var(--brand-soft); color: var(--brand); border-radius: 10px; font-weight: 900; }.flow small { color: var(--muted); margin-top: 4px; }.flow i { font-style: normal; color: var(--brand); }
.evaluation-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 16px; margin-top: 28px; }.evaluation-grid article { background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius-sm); padding: 22px; }.evaluation-grid span { width: 34px; height: 34px; border-radius: 10px; display: grid; place-items: center; background: var(--violet-soft); color: var(--violet); font-weight: 900; }.evaluation-grid h3 { margin: 14px 0 6px; }.evaluation-grid p { margin: 0; color: var(--muted); font-size: .92rem; }
.do-dont { display: grid; grid-template-columns: 1fr 1fr; gap: 18px; margin-top: 28px; }.do-dont article { padding: 24px; border-radius: var(--radius); }.do { background: var(--green-soft); }.dont { background: color-mix(in srgb, #e35656 12%, var(--surface)); }.do h3 { color: var(--green); }.dont h3 { color: var(--red); }.do-dont li { margin: 8px 0; }
.content-image { margin: 30px 0; }.content-image img { display: block; border-radius: var(--radius); border: 1px solid var(--line); box-shadow: var(--shadow-sm); }.content-image figcaption { color: var(--muted); font-size: .85rem; margin-top: 10px; }
.sources-section { border-top: 1px solid var(--line); padding-top: 50px; }.source-list { padding-left: 20px; }.source-list li { margin: 10px 0; }.source-list a { color: var(--brand); }
.chapter-next { border-top: 1px solid var(--line); padding-top: 30px; display: grid; gap: 8px; }.chapter-next > span { color: var(--muted); font-size: .78rem; text-transform: uppercase; letter-spacing: .08em; font-weight: 800; }.chapter-next a { display: flex; justify-content: space-between; align-items: center; color: var(--text); text-decoration: none; font-size: 1.35rem; transition: color .2s, transform .25s var(--ease-out); }.chapter-next a:hover { color: var(--brand); transform: translateX(5px); }.chapter-next b { color: var(--brand); font-size: 1.7rem; transition: transform .25s var(--ease-out); }.chapter-next a:hover b { transform: translateX(5px); }

.quiz-main { min-height: 70vh; }.quiz-hero { padding: 70px 0 40px; text-align: center; }.quiz-hero .breadcrumbs { justify-content: center; }.quiz-hero h1 { font-size: clamp(2.6rem, 5vw, 4.8rem); }.quiz-hero p:last-child { color: var(--muted); max-width: 730px; margin-inline: auto; }
.quiz-section { padding-top: 24px; }.quiz-shell { max-width: 850px; }.quiz-start, .quiz-play, .quiz-result { background: var(--surface); border: 1px solid var(--line); border-radius: 28px; padding: clamp(28px, 5vw, 54px); box-shadow: var(--shadow); }.quiz-start, .quiz-result { text-align: center; }.quiz-start-icon, .result-icon { font-size: 3.2rem; }.quiz-start h2, .quiz-result h2 { margin: 18px 0 12px; }.quiz-start > p, .quiz-result > p { color: var(--muted); }.quiz-meta { display: grid; grid-template-columns: repeat(3, 1fr); border: 1px solid var(--line); border-radius: var(--radius-sm); margin: 28px 0; overflow: hidden; }.quiz-meta div { padding: 18px; display: grid; }.quiz-meta div + div { border-left: 1px solid var(--line); }.quiz-meta strong { font-size: 1.6rem; }.quiz-meta span { color: var(--muted); font-size: .82rem; }
.quiz-topline, .quiz-topline > div { display: flex; align-items: center; justify-content: space-between; gap: 12px; }.topic-pill { background: var(--brand-soft); color: var(--brand); border-radius: 999px; padding: 7px 11px; font-size: .74rem; font-weight: 900; text-transform: uppercase; letter-spacing: .05em; }.quiz-timer { color: var(--muted); font-weight: 800; }.progress-track { height: 8px; background: var(--surface-2); border-radius: 999px; margin: 22px 0 34px; overflow: hidden; }.progress-value { height: 100%; width: 12.5%; background: linear-gradient(90deg, var(--brand-2), var(--brand)); border-radius: inherit; transition: width .25s; }.question-area h2 { font-size: clamp(1.45rem, 3vw, 2.25rem); }.answer-grid { display: grid; gap: 12px; margin-top: 24px; }.answer-button { width: 100%; display: grid; grid-template-columns: 36px 1fr; align-items: center; gap: 12px; text-align: left; background: var(--surface); border: 1px solid var(--line); border-radius: 14px; padding: 14px 16px; cursor: pointer; color: var(--text); transition: border-color .18s, transform .18s, background .18s; }.answer-button:hover:not(:disabled) { border-color: var(--brand); transform: translateX(3px); }.answer-button b { width: 34px; height: 34px; display: grid; place-items: center; border-radius: 9px; background: var(--surface-2); }.answer-button.correct { border-color: var(--green); background: var(--green-soft); }.answer-button.wrong { border-color: var(--red); background: color-mix(in srgb, #e35656 12%, var(--surface)); }.answer-button:disabled { cursor: default; }.quiz-feedback { margin-top: 22px; padding: 18px; border-radius: var(--radius-sm); background: var(--surface-2); border-left: 4px solid var(--brand); }.quiz-feedback p { margin: 5px 0 0; color: var(--muted); }.quiz-actions { display: flex; justify-content: flex-end; margin-top: 24px; }
.result-score { width: 170px; height: 170px; border-radius: 50%; display: grid; place-items: center; align-content: center; margin: 26px auto; background: var(--brand-soft); border: 10px solid color-mix(in srgb, var(--brand) 18%, var(--surface)); }.result-score strong { font-size: 3.3rem; line-height: 1; color: var(--brand); }.result-score span { color: var(--muted); font-size: .82rem; }.result-stats { display: grid; grid-template-columns: repeat(3, 1fr); border: 1px solid var(--line); border-radius: var(--radius-sm); overflow: hidden; }.result-stats div { padding: 17px; display: grid; }.result-stats div + div { border-left: 1px solid var(--line); }.result-stats span { color: var(--muted); font-size: .78rem; }.mini-links { display: grid; grid-template-columns: repeat(3, 1fr); gap: 16px; margin-top: 30px; }.mini-links a { display: grid; background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius-sm); padding: 22px; color: var(--text); text-decoration: none; transition: transform .28s var(--ease-out), border-color .28s, box-shadow .28s; }.mini-links a:hover { transform: translateY(-5px); border-color: var(--brand); box-shadow: var(--shadow-sm); }.mini-links span { font-size: 1.5rem; }.mini-links strong { margin: 8px 0 3px; }.mini-links small { color: var(--muted); }

.reveal-ready { opacity: 0; transform: translateY(28px); transition: opacity .7s var(--ease-out), transform .7s var(--ease-out); }
.reveal-ready.revealed { opacity: 1; transform: translateY(0); }
.back-to-top { position: fixed; right: 22px; bottom: 22px; z-index: 45; width: 46px; height: 46px; display: grid; place-items: center; border: 1px solid color-mix(in srgb, var(--brand) 35%, var(--line)); border-radius: 14px; background: color-mix(in srgb, var(--surface) 92%, transparent); color: var(--brand); box-shadow: var(--shadow); backdrop-filter: blur(12px); cursor: pointer; opacity: 0; visibility: hidden; transform: translateY(14px); transition: opacity .25s, visibility .25s, transform .25s var(--ease-out), background .25s; }
.back-to-top.visible { opacity: 1; visibility: visible; transform: translateY(0); }
.back-to-top:hover { background: var(--brand); color: white; transform: translateY(-3px); }

.site-footer { background: #09101d; color: #e8effb; padding: 64px 0 20px; }.footer-grid { display: grid; grid-template-columns: 1.4fr .7fr 1fr; gap: 56px; }.footer-brand { color: white; margin-bottom: 18px; }.footer-brand img { width: 42px; height: 42px; border-radius: 13px; }.site-footer p { color: #9eacc0; }.site-footer h2 { font-size: .82rem; text-transform: uppercase; letter-spacing: .1em; color: #dce7f6; margin-bottom: 16px; }.site-footer > .container a:not(.brand) { color: #aebbd0; text-decoration: none; display: block; margin: 8px 0; }.site-footer > .container a:hover { color: white; }.footer-note { font-size: .82rem; }.footer-bottom { border-top: 1px solid #243147; margin-top: 40px; padding-top: 18px; display: flex; justify-content: space-between; color: #8392a8; font-size: .82rem; }.footer-bottom a { display: inline !important; margin: 0 !important; }
.student-credits-trigger { appearance: none; border: 0; border-radius: 5px; padding: 2px 3px; margin: -2px -3px; background: transparent; color: #aebbd0; cursor: pointer; font: inherit; text-decoration: underline dotted; text-decoration-color: color-mix(in srgb, #aebbd0 60%, transparent); text-underline-offset: 4px; transition: color .2s, background .2s; }
.student-credits-trigger:hover { color: white; background: rgba(127, 156, 255, .1); }
.dialog-open { overflow: hidden; }
.student-credits-dialog { width: min(calc(100% - 32px), 620px); max-height: min(760px, calc(100dvh - 32px)); padding: 0; border: 1px solid color-mix(in srgb, var(--brand) 35%, var(--line)); border-radius: 26px; background: transparent; color: var(--text); box-shadow: 0 38px 100px rgba(0, 0, 0, .42); overflow: hidden; }
.student-credits-dialog::backdrop { background: rgba(3, 8, 20, .72); backdrop-filter: blur(8px); }
.student-credits-dialog[open] { animation: student-dialog-in .34s var(--ease-out); }
.student-credits-card { position: relative; overflow: auto; max-height: min(760px, calc(100dvh - 32px)); padding: clamp(28px, 6vw, 48px); background: radial-gradient(circle at 90% 4%, color-mix(in srgb, var(--brand-2) 18%, transparent), transparent 34%), var(--surface); }
.student-credits-card::before { content: ""; position: absolute; inset: 0 auto 0 0; width: 4px; background: linear-gradient(var(--brand-2), var(--brand), var(--violet)); }
.student-credits-close { position: absolute; top: 18px; right: 18px; width: 42px; height: 42px; border: 1px solid var(--line); border-radius: 12px; background: color-mix(in srgb, var(--surface) 88%, transparent); color: var(--muted); cursor: pointer; font-size: 1.6rem; line-height: 1; transition: transform .22s var(--ease-out), color .22s, border-color .22s, background .22s; }
.student-credits-close:hover { transform: rotate(6deg) scale(1.05); color: var(--text); border-color: var(--brand); background: var(--surface-2); }
.student-credits-kicker { margin: 0 56px 8px 0; color: var(--brand); font-weight: 900; font-size: .73rem; letter-spacing: .11em; text-transform: uppercase; }
.student-credits-dialog h2 { margin: 0 52px 12px 0; font-size: clamp(2rem, 6vw, 3.2rem); }
.student-credits-intro { max-width: 510px; margin: 0 0 26px; color: var(--muted); }
.student-name-list { display: grid; grid-template-columns: repeat(4, minmax(0, 1fr)); gap: 10px; margin: 0; padding: 0; list-style: none; }
.student-name-list li { min-height: 46px; display: grid; place-items: center; padding: 9px 12px; border: 1px solid color-mix(in srgb, var(--brand) 30%, var(--line)); border-radius: 13px; background: var(--brand-soft); color: var(--brand); font-weight: 850; text-align: center; }
.student-name-list li.placeholder { border-style: dashed; background: var(--surface-2); color: var(--muted); font-weight: 700; }
.student-consent-note { display: flex; gap: 9px; align-items: flex-start; margin: 24px 0 0; padding-top: 18px; border-top: 1px solid var(--line); color: var(--muted) !important; font-size: .82rem; }
.student-consent-note span { color: var(--green); font-size: .68rem; margin-top: 5px; }
@keyframes student-dialog-in { from { opacity: 0; transform: translateY(18px) scale(.97); } to { opacity: 1; transform: translateY(0) scale(1); } }

@media (max-width: 980px) {
  .main-nav { position: fixed; inset: 89px 20px auto; background: var(--surface); border: 1px solid var(--line); border-radius: 18px; padding: 12px; box-shadow: var(--shadow); display: none; flex-direction: column; align-items: stretch; }
  .main-nav.open { display: flex; }.main-nav .nav-quiz { margin-left: 0; text-align: center; }.nav-toggle { display: grid; margin-left: auto; }.theme-toggle { flex-shrink: 0; }
  .hero-grid { grid-template-columns: 1fr; }.hero-copy { max-width: 780px; }.hero-photo { width: min(100%, 860px); }.hero-photo-frame { min-height: 430px; aspect-ratio: 16 / 9; transform: rotate(.3deg); }.feature-grid, .glossary-grid { grid-template-columns: 1fr 1fr; }.split-grid { grid-template-columns: 1fr; }
  .chapter-layout { grid-template-columns: 1fr; gap: 36px; }.toc { position: static; display: flex; flex-wrap: wrap; border-left: 0; border-bottom: 1px solid var(--line); padding: 0 0 18px; }.toc strong { flex-basis: 100%; }.toc a { background: var(--surface-2); }
  .sim-grid, .inspection-card { grid-template-columns: 1fr; }.signal-stage { min-height: 300px; }.range-grid { grid-template-columns: 1fr 1fr; }.range-grid label:last-child { grid-column: 1 / -1; }
}

@media (max-width: 720px) {
  .container { width: min(calc(100% - 28px), var(--container)); }.nav-wrap { min-height: 76px; }.main-nav { inset: 77px 14px auto; }.site-header .brand img { width: 50px; height: 50px; border-radius: 14px; }.brand small { display: none; }
  .hero { padding: 62px 0; }.hero-copy, .hero-photo { width: 100%; min-width: 0; }.hero-photo-frame { width: 100%; min-height: 0; aspect-ratio: 4 / 3; border-radius: 24px; transform: none; }.hero-photo-frame::before { inset: 8px -8px -8px 8px; }.hero-photo-frame img { object-position: 64% center; }.hero-topic-links { gap: 7px; margin-top: 16px; }.visual-card { padding: 9px 7px; font-size: .72rem; gap: 5px; }.visual-card span { font-size: 1rem; }.hero-facts { gap: 12px; flex-wrap: wrap; }.hero-facts li { min-width: 120px; }
  .section { padding: 64px 0; }.feature-grid, .glossary-grid, .info-grid.three, .threat-grid, .evaluation-grid, .mini-links { grid-template-columns: 1fr; }.feature-card { min-height: 285px; }
  .page-hero { padding: 48px 0; }.page-hero-grid { grid-template-columns: 1fr; }.chapter-badge { display: none; }.chapter-layout { padding-top: 44px; padding-bottom: 64px; }.content-section { margin-bottom: 64px; }
  .material-list article { grid-template-columns: 1fr; }.level { width: max-content; }.versus-grid, .result-compare, .principle-grid, .do-dont { grid-template-columns: 1fr; }.range-grid { grid-template-columns: 1fr; }.range-grid label:last-child { grid-column: auto; }
  .signal-stage { padding: 28px 20px; }.wall { left: 52%; height: 200px; }.router-node span, .device-node span { font-size: 2.3rem; }.wave-lines { left: 45px; transform: translateY(-50%) scale(.75); transform-origin: left center; }.signal-meter { right: 18px; top: 20px; }
  .backup-visual, .flow { grid-template-columns: 1fr; }.backup-visual i, .flow i { transform: rotate(90deg); text-align: center; }.result-stats, .quiz-meta { grid-template-columns: 1fr; }.result-stats div + div, .quiz-meta div + div { border-left: 0; border-top: 1px solid var(--line); }
  .quiz-start, .quiz-play, .quiz-result { border-radius: 20px; }.quiz-topline { align-items: flex-start; }.quiz-topline > div { align-items: flex-start; flex-direction: column; }.answer-button { grid-template-columns: 32px 1fr; }
  .footer-grid { grid-template-columns: 1fr; gap: 30px; }.footer-bottom { flex-direction: column; gap: 8px; }.back-to-top { right: 14px; bottom: 14px; }
  .student-name-list { grid-template-columns: repeat(2, minmax(0, 1fr)); }
}

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { scroll-behavior: auto !important; animation-duration: .01ms !important; animation-iteration-count: 1 !important; transition-duration: .01ms !important; }
  .reveal-ready { opacity: 1; transform: none; }
}