/* ============================================
   KTN – Shared Stylesheet
   TTM4100 Kommunikasjon - Tjenester og nett
   ============================================ */

/* ---------- FONTS ---------- */
@import url('https://fonts.googleapis.com/css2?family=Newsreader:ital,opsz,wght@0,6..72,300;0,6..72,400;0,6..72,500;0,6..72,700;1,6..72,400;1,6..72,500&family=IBM+Plex+Mono:wght@400;500;700&family=IBM+Plex+Sans:wght@400;500;600&display=swap');

/* ---------- VARIABLES ---------- */
:root {
  --paper: #f4f1ea;
  --paper-dark: #e8e3d6;
  --paper-darker: #ddd5c4;
  --ink: #1a1612;
  --ink-soft: #3d3832;
  --ink-faded: #6b6257;
  --ink-ghost: #a39886;
  --rust: #b04428;
  --rust-dark: #8a3420;
  --blue: #2d4a7a;
  --green: #3d6b3a;
  --ochre: #c68a1f;
  --line: #c9c0ae;
  --line-soft: #ddd5c4;
  --serif: 'Newsreader', Georgia, serif;
  --mono: 'IBM Plex Mono', Menlo, monospace;
  --sans: 'IBM Plex Sans', system-ui, sans-serif;
  --packet-hl: #f5eae5;
}

/* ---------- RESET ---------- */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; }

body {
  font-family: var(--serif);
  font-size: 18px;
  line-height: 1.7;
  color: var(--ink);
  background: var(--paper);
  -webkit-font-smoothing: antialiased;
  font-feature-settings: "kern", "liga";
  position: relative;
}

/* Paper texture overlay */
body::before {
  content: "";
  position: fixed;
  inset: 0;
  background-image: url("data:image/svg+xml,%3Csvg viewBox='0 0 200 200' xmlns='http://www.w3.org/2000/svg'%3E%3Cfilter id='n'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='0.85' numOctaves='2' stitchTiles='stitch'/%3E%3CfeColorMatrix values='0 0 0 0 0.42 0 0 0 0 0.38 0 0 0 0 0.33 0 0 0 0.4 0'/%3E%3C/filter%3E%3Crect width='100%25' height='100%25' filter='url(%23n)'/%3E%3C/svg%3E");
  opacity: 0.35;
  pointer-events: none;
  z-index: 1;
  mix-blend-mode: multiply;
}

/* ---------- LAYOUT ---------- */
.container {
  max-width: 820px;
  margin: 0 auto;
  padding: 0 32px;
  position: relative;
  z-index: 2;
}
.container-wide,
.container.wide {
  max-width: 1000px;
  margin: 0 auto;
  padding: 0 32px;
  position: relative;
  z-index: 2;
}

/* ---------- SITE NAV ---------- */
.site-nav {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(244, 241, 234, 0.92);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--line);
  padding: 14px 0;
}
.site-nav .container {
  display: flex;
  align-items: center;
  justify-content: space-between;
}
.site-nav .brand {
  font-family: var(--mono);
  font-size: 13px;
  font-weight: 700;
  letter-spacing: 0.1em;
  color: var(--rust);
  text-decoration: none;
}
.site-nav .brand:hover { color: var(--rust-dark); }
.site-nav .nav-back {
  font-family: var(--sans);
  font-size: 13px;
  font-weight: 500;
  color: var(--ink-faded);
  text-decoration: none;
  display: flex;
  align-items: center;
  gap: 6px;
  transition: color 0.15s;
}
.site-nav .nav-back:hover { color: var(--rust); }

/* ---------- HERO ---------- */
.hero {
  padding: 100px 0 70px;
  border-bottom: 1px solid var(--line);
}
.hero .eyebrow {
  font-family: var(--mono);
  font-size: 12px;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--rust);
  margin-bottom: 28px;
  display: inline-block;
}
.hero h1 {
  font-family: var(--serif);
  font-size: clamp(44px, 7vw, 84px);
  font-weight: 500;
  line-height: 1.02;
  letter-spacing: -0.025em;
  margin-bottom: 28px;
}
.hero h1 em {
  font-style: italic;
  font-weight: 400;
  color: var(--rust);
}
.hero h1 .reg { font-style: normal; }
.hero .subtitle {
  font-family: var(--serif);
  font-style: italic;
  font-size: 22px;
  line-height: 1.45;
  color: var(--ink-soft);
  max-width: 640px;
  margin-bottom: 40px;
}
.hero .sub,
.hero .lede {
  font-size: 22px;
  line-height: 1.5;
  color: var(--ink-soft);
  font-style: italic;
  max-width: 650px;
  margin-bottom: 40px;
}

/* TOC in hero */
.toc {
  border-top: 1px solid var(--line);
  padding-top: 28px;
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 6px 40px;
  font-family: var(--sans);
  font-size: 14px;
  color: var(--ink-faded);
}
.toc a {
  color: var(--ink-soft);
  text-decoration: none;
  display: flex;
  align-items: baseline;
  gap: 14px;
  padding: 8px 0;
  border-bottom: 1px solid var(--line-soft);
  transition: color 0.15s, padding-left 0.15s;
}
.toc a:hover { color: var(--rust); padding-left: 6px; }
.toc a span:first-child,
.toc .toc-num {
  font-family: var(--mono);
  color: var(--ink-ghost);
  font-size: 12px;
  min-width: 20px;
}

/* "What you'll learn" box in hero */
.hero .learn-box,
.hero .what-youll-learn {
  border-top: 1px solid var(--line);
  padding: 24px 0;
  margin-top: 40px;
  max-width: 680px;
}
.hero .learn-box .label,
.hero .what-youll-learn .label {
  font-family: var(--sans);
  font-size: 11px;
  letter-spacing: 0.2em;
  text-transform: uppercase;
  color: var(--ink-ghost);
  margin-bottom: 12px;
  font-weight: 600;
}
.hero .learn-box ul,
.hero .what-youll-learn ul {
  list-style: none;
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 10px 28px;
}
.hero .learn-box li,
.hero .what-youll-learn li {
  font-size: 16px;
  color: var(--ink-soft);
  padding-left: 20px;
  position: relative;
}
.hero .learn-box li::before,
.hero .what-youll-learn li::before {
  content: '\2733';
  position: absolute;
  left: 0;
  color: var(--rust);
  font-size: 12px;
  top: 3px;
}

/* ---------- SECTIONS ---------- */
section {
  padding: 80px 0;
  border-bottom: 1px solid var(--line);
}
.badge,
.section-badge,
.section-number {
  font-family: var(--mono);
  font-size: 12px;
  letter-spacing: 0.15em;
  text-transform: uppercase;
  color: var(--ink-faded);
  display: inline-block;
  padding: 6px 14px;
  border: 1px solid var(--line);
  border-radius: 2px;
  margin-bottom: 28px;
  background: var(--paper);
}

/* ---------- TYPOGRAPHY ---------- */
h2 {
  font-family: var(--serif);
  font-size: clamp(32px, 4.5vw, 50px);
  font-weight: 500;
  line-height: 1.1;
  letter-spacing: -0.018em;
  margin-bottom: 18px;
}
h2 em { font-style: italic; color: var(--rust); font-weight: 400; }
.section-intro {
  font-family: var(--serif);
  font-style: italic;
  font-size: 20px;
  line-height: 1.5;
  color: var(--ink-soft);
  margin-bottom: 40px;
  max-width: 680px;
}
h3 {
  font-family: var(--serif);
  font-size: 26px;
  font-weight: 500;
  line-height: 1.25;
  margin: 52px 0 16px;
  letter-spacing: -0.01em;
}
h4 {
  font-family: var(--sans);
  font-size: 14px;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--rust);
  margin: 32px 0 12px;
}
p { margin-bottom: 20px; }
p strong, strong { font-weight: 600; color: var(--ink); }
p em, em { font-style: italic; }
a { color: var(--rust); text-decoration: underline; text-decoration-color: var(--line); text-underline-offset: 3px; }
a:hover { text-decoration-color: var(--rust); }

/* Drop cap */
.dropcap::first-letter,
p.lead::first-letter {
  font-family: var(--serif);
  font-size: 5.2em;
  float: left;
  line-height: 0.85;
  padding: 8px 10px 0 0;
  color: var(--rust);
  font-weight: 500;
}

/* Inline code */
code, .mono {
  font-family: var(--mono);
  font-size: 0.88em;
  background: var(--paper-dark);
  padding: 2px 6px;
  border-radius: 2px;
  color: var(--rust-dark);
}

ul, ol { margin: 0 0 20px 24px; }
li { margin-bottom: 8px; }

/* ---------- MARGIN NOTES ---------- */
.margin-note {
  border-left: 3px solid var(--ochre);
  padding: 4px 0 4px 20px;
  margin: 28px 0;
  font-style: italic;
  color: var(--ink-soft);
  font-size: 16px;
  line-height: 1.55;
}
.margin-note strong { color: var(--ink-soft); font-style: normal; }

/* ---------- CALLOUTS / BOXES ---------- */
.callout,
.box {
  background: var(--paper-dark);
  border-left: 4px solid var(--rust);
  padding: 24px 28px;
  margin: 32px 0;
  border-radius: 0 2px 2px 0;
}
.callout h4, .box h4 { margin-top: 0; color: var(--rust-dark); }
.callout p:last-child, .box p:last-child { margin-bottom: 0; }
.callout-blue, .box.blue { border-left-color: var(--blue); }
.callout-blue h4, .box.blue h4, .box.blue .label { color: var(--blue); }
.callout-green, .box.green { border-left-color: var(--green); }
.callout-green h4, .box.green h4, .box.green .label { color: var(--green); }
.box.ochre { border-left-color: var(--ochre); }
.box.ochre .label { color: var(--ochre); }
.box .label, .callout .label {
  font-family: var(--mono);
  font-size: 11px;
  letter-spacing: 0.15em;
  text-transform: uppercase;
  color: var(--rust);
  margin-bottom: 10px;
  display: block;
}

.box.insight { border-left-color: var(--blue); }
.box.insight .label { color: var(--blue); }
.box.solution { border-left-color: var(--green); }
.box.solution .label { color: var(--green); }
.box.problem { border-left-color: var(--rust); }
.box.problem .label { color: var(--rust); }

/* Info box variant */
.info-box {
  background: var(--paper-dark);
  border: 1px solid var(--line);
  padding: 24px 28px;
  margin: 32px 0;
  position: relative;
}
.info-box::before {
  content: '';
  position: absolute;
  top: 0; left: 0;
  width: 4px; height: 100%;
  background: var(--rust);
}
.info-box h4 { margin-top: 0; margin-bottom: 12px; }
.info-box p:last-child { margin-bottom: 0; }
.info-box.blue::before { background: var(--blue); }
.info-box.blue h4 { color: var(--blue); }
.info-box.green::before { background: var(--green); }
.info-box.green h4 { color: var(--green); }

/* Problem box */
.problem-box {
  border: 1px solid var(--line);
  background: rgba(176, 68, 40, 0.04);
  padding: 22px 26px;
  margin: 28px 0;
}
.problem-box .label {
  font-family: var(--mono);
  font-size: 11px;
  text-transform: uppercase;
  letter-spacing: 0.15em;
  color: var(--rust);
  margin-bottom: 8px;
}

/* ---------- SVG WRAPPERS ---------- */
.svg-wrap,
.fsm-wrap {
  overflow-x: auto;
}

/* ---------- FIGURES ---------- */
figure {
  margin: 40px 0;
  padding: 24px;
  background: var(--paper-dark);
  border: 1px solid var(--line);
  border-radius: 2px;
}
figure svg { display: block; margin: 0 auto; max-width: 100%; height: auto; }
figcaption {
  font-family: var(--serif);
  font-style: italic;
  font-size: 14px;
  color: var(--ink-faded);
  text-align: center;
  margin-top: 14px;
  line-height: 1.5;
}
figcaption strong { font-style: normal; color: var(--ink-soft); }

/* Figure frame variant */
.fig-frame {
  border: 1px solid var(--line);
  background: var(--paper);
  padding: 28px;
}

/* ---------- PACKET HEADER DIAGRAM ---------- */
figure:has(.packet) {
  padding: 0;
  overflow-x: auto;
}
figure:has(.packet) figcaption {
  padding: 12px 16px 16px;
}
.packet {
  display: grid;
  grid-template-columns: repeat(32, 1fr);
  border-top: 1px solid var(--line);
  border-left: 1px solid var(--line);
  font-family: var(--sans);
  background: var(--paper);
  min-width: 480px;
}
.packet .cell {
  border-right: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
  padding: 8px 4px;
  text-align: center;
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 52px;
}
.packet .cell > div {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 2px;
}
.packet .cell > div strong {
  font-family: var(--sans);
  font-size: 12px;
  font-weight: 600;
  line-height: 1.2;
  color: var(--ink);
}
.packet .cell > div small {
  font-family: var(--mono);
  font-size: 10px;
  color: var(--ink-faded);
  line-height: 1.2;
}
.packet .cell.c4  { grid-column: span 4; }
.packet .cell.c8  { grid-column: span 8; }
.packet .cell.c16 { grid-column: span 16; }
.packet .cell.c32 { grid-column: span 32; }
.packet .cell.c3  { grid-column: span 3; }
.packet .cell.c13 { grid-column: span 13; }
.packet .cell.hl  { background: var(--packet-hl); }
.packet .cell.data {
  background: var(--paper-dark);
  font-family: var(--sans);
  font-style: italic;
  font-size: 13px;
  color: var(--ink-faded);
  min-height: 44px;
}

/* ---------- TABLES ---------- */
table {
  width: 100%;
  border-collapse: collapse;
  margin: 28px 0;
  font-size: 16px;
}
th, td {
  padding: 12px 16px;
  text-align: left;
  border-bottom: 1px solid var(--line-soft);
  vertical-align: top;
}
th {
  font-family: var(--sans);
  font-weight: 600;
  font-size: 12px;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--ink-faded);
  background: var(--paper-dark);
  border-bottom: 2px solid var(--line);
}
tbody tr:hover { background: rgba(176, 68, 40, 0.04); }
td.mono-cell,
td.label-col {
  font-family: var(--mono);
  font-size: 14px;
  color: var(--rust-dark);
}

/* Compare table variant */
.compare,
.compare-table {
  background: var(--paper);
  border: 1px solid var(--line);
}
.compare td:first-child,
.compare-table td:first-child {
  font-weight: 500;
  color: var(--ink);
  width: 28%;
}

/* ---------- CODE BLOCKS ---------- */
pre {
  font-family: var(--mono);
  font-size: 13px;
  line-height: 1.55;
  background: #1a1612;
  color: #e8e3d6;
  padding: 20px 24px;
  border-radius: 3px;
  overflow-x: auto;
  margin: 24px 0;
}
pre code { background: none; color: inherit; padding: 0; }
pre .comment, pre .c-cmt { color: #8a7f6b; font-style: italic; }
pre .keyword, pre .kw, pre .c-key { color: #c68a1f; }
pre .value, pre .c-srv { color: #9fb56b; }
pre .c-cli { color: #e8b560; }

#stepper-smtp .stage pre {
  margin: 0;
}
#stepper-smtp pre .smtp-line {
  display: block;
}

/* ---------- DIVIDERS ---------- */
.divider,
.ornament {
  text-align: center;
  color: var(--rust);
  font-size: 18px;
  letter-spacing: 1em;
  margin: 56px 0;
}

/* ---------- QUIZ ---------- */
.quiz {
  background: var(--paper-dark);
  border: 1px solid var(--line);
  border-radius: 3px;
  padding: 28px 32px;
  margin: 40px 0;
}
.quiz .label,
.quiz .q-label,
.quiz .qlabel {
  font-family: var(--mono);
  font-size: 11px;
  letter-spacing: 0.15em;
  text-transform: uppercase;
  color: var(--rust);
  margin-bottom: 10px;
}
.quiz .question,
.quiz .q-text {
  font-family: var(--serif);
  font-size: 19px;
  font-weight: 500;
  margin-bottom: 20px;
  line-height: 1.4;
  color: var(--ink);
}
.quiz .options,
.quiz .opts { display: flex; flex-direction: column; gap: 10px; }
.quiz button.opt,
.quiz button.option {
  font-family: var(--serif);
  font-size: 16px;
  text-align: left;
  background: var(--paper);
  border: 1px solid var(--line);
  padding: 14px 18px;
  cursor: pointer;
  border-radius: 2px;
  color: var(--ink);
  transition: all 0.15s;
  line-height: 1.4;
}
.quiz button.opt:hover,
.quiz button.option:hover { border-color: var(--rust); background: #fff9ee; }
.quiz button.opt.correct,
.quiz button.option.correct {
  background: #e8efe0;
  border-color: var(--green);
  color: var(--green);
}
.quiz button.opt.wrong,
.quiz button.opt.incorrect,
.quiz button.option.incorrect {
  background: #f3e0dc;
  border-color: var(--rust);
  color: var(--rust-dark);
}
.quiz button.opt:disabled,
.quiz button.option:disabled { cursor: default; }
.quiz .explain,
.quiz .feedback,
.quiz .explanation {
  margin-top: 18px;
  padding: 14px 18px;
  background: var(--paper);
  border-left: 3px solid var(--green);
  font-size: 15px;
  font-style: italic;
  color: var(--ink-soft);
  display: none;
}
.quiz .explain.show,
.quiz .feedback.show,
.quiz .explanation.show { display: block; }

/* ---------- STEPPER ---------- */
.stepper {
  background: var(--paper-dark);
  border: 1px solid var(--line);
  border-radius: 3px;
  padding: 28px 32px;
  margin: 40px 0;
}
.stepper .label,
.stepper .s-label {
  font-family: var(--mono);
  font-size: 11px;
  letter-spacing: 0.15em;
  text-transform: uppercase;
  color: var(--rust);
  margin-bottom: 14px;
}
.stepper .stage {
  background: var(--paper);
  border: 1px solid var(--line);
  border-radius: 2px;
  padding: 20px 24px;
  min-height: 120px;
}
.stepper .stage h5 {
  font-family: var(--serif);
  font-size: 20px;
  font-weight: 500;
  margin-bottom: 12px;
  color: var(--rust);
}
.stepper .stage p {
  font-size: 16px;
  margin-bottom: 0;
  line-height: 1.55;
}
.step-desc {
  font-family: var(--serif);
  font-size: 17px;
  font-style: italic;
  color: var(--ink-soft);
  min-height: 52px;
  margin-top: 14px;
  line-height: 1.5;
}
.stepper-controls,
.stepper .controls {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-top: 18px;
  padding-top: 16px;
  border-top: 1px solid var(--line);
  gap: 12px;
}
.stepper-controls button,
.stepper button {
  font-family: var(--sans);
  font-size: 13px;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  padding: 10px 20px;
  background: var(--ink);
  color: var(--paper);
  border: none;
  cursor: pointer;
  border-radius: 2px;
  transition: background 0.15s;
}
.stepper-controls button:hover:not(:disabled),
.stepper button:hover:not(:disabled) { background: var(--rust); }
.stepper-controls button:disabled,
.stepper button:disabled { opacity: 0.3; cursor: not-allowed; }
.stepper-controls .counter,
.stepper .progress {
  font-family: var(--mono);
  font-size: 13px;
  color: var(--ink-faded);
}

/* ---------- SLIDER / INTERACTIVE ---------- */
.slider-box {
  background: var(--paper-dark);
  border: 1px solid var(--line);
  border-radius: 3px;
  padding: 28px 32px;
  margin: 40px 0;
}
.slider-box .label,
.slider-box .s-label {
  font-family: var(--mono);
  font-size: 11px;
  letter-spacing: 0.15em;
  text-transform: uppercase;
  color: var(--rust);
  margin-bottom: 14px;
}
.slider-box label {
  font-family: var(--sans);
  font-size: 13px;
  font-weight: 600;
  display: block;
  margin: 18px 0 8px;
  color: var(--ink-soft);
}
.slider-box input[type=range] {
  width: 100%;
  accent-color: var(--rust);
}
.slider-box .readout {
  font-family: var(--mono);
  font-size: 15px;
  margin-top: 14px;
  padding: 14px 18px;
  background: var(--paper);
  border-left: 3px solid var(--rust);
  color: var(--ink-soft);
}
.slider-box .readout strong { color: var(--rust); font-weight: 700; }

/* CIDR / address display */
.addr-display {
  font-family: var(--mono);
  font-size: 15px;
  background: #1a1612;
  color: var(--paper);
  padding: 14px 18px;
  border-radius: 3px;
  margin: 12px 0;
  overflow-x: auto;
  white-space: nowrap;
}
.addr-display .net { color: #f5d76e; }
.addr-display .host { color: #8ab0ff; }

/* Stats grid */
.stats {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 12px;
  margin-top: 14px;
}
.stats div {
  background: var(--paper-dark);
  padding: 12px;
  text-align: center;
  border-radius: 2px;
}
.stats .k {
  font-family: var(--mono);
  font-size: 11px;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--ink-faded);
  margin-bottom: 4px;
}
.stats .v {
  font-family: var(--mono);
  font-size: 18px;
  color: var(--rust);
  font-weight: 700;
}

/* Simulator */
.simulator {
  border: 1px solid var(--line);
  background: var(--paper);
  padding: 32px;
  margin: 40px 0;
}
.simulator h4 { margin-top: 0; color: var(--blue); font-size: 12px; }
.sim-controls {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 20px 28px;
  margin-bottom: 20px;
  align-items: start;
}
.sim-control {
  display: flex;
  flex-direction: column;
  align-items: stretch;
  gap: 10px;
  min-width: 0;
}
.sim-control label {
  display: block;
  font-family: var(--sans);
  font-size: 14px;
  font-weight: 600;
  color: var(--ink-soft);
  line-height: 1.4;
}
.sim-control label .val {
  font-family: var(--mono);
  font-weight: 700;
  color: var(--ink);
  white-space: nowrap;
}
.simulator input[type="range"] {
  width: 100%;
  max-width: 100%;
  accent-color: var(--rust);
  cursor: pointer;
  height: 1.25rem;
}
.sim-results {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 14px 20px;
  margin-bottom: 22px;
  max-width: 520px;
}
.sim-result-block {
  background: var(--paper-dark);
  border: 1px solid var(--line);
  border-radius: 3px;
  padding: 14px 18px;
  border-left: 3px solid var(--line);
}
.sim-result-block.cs {
  border-left-color: var(--rust);
}
.sim-result-block.p2p {
  border-left-color: var(--green);
}
.sim-result-block .lbl {
  font-family: var(--mono);
  font-size: 11px;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--ink-faded);
  margin-bottom: 6px;
}
.sim-result-block .num {
  font-family: var(--mono);
  font-size: 22px;
  font-weight: 700;
  line-height: 1.2;
  color: var(--ink);
}
.sim-result-block.cs .num {
  color: var(--rust);
}
.sim-result-block.p2p .num {
  color: var(--green);
}
#sim-chart {
  width: 100%;
  max-width: 600px;
  height: auto;
  display: block;
  margin: 8px auto 0;
}

/* ---------- REVEAL ---------- */
.reveal {
  margin: 28px 0;
  border: 1px dashed var(--line);
  border-radius: 3px;
  padding: 20px 24px;
  background: rgba(255,255,255,0.4);
}
.reveal .q {
  font-style: italic;
  color: var(--ink-soft);
  margin-bottom: 12px;
}
.reveal button {
  font-family: var(--mono);
  font-size: 12px;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  padding: 8px 16px;
  background: transparent;
  border: 1px solid var(--rust);
  color: var(--rust);
  cursor: pointer;
  border-radius: 2px;
}
.reveal button:hover { background: var(--rust); color: var(--paper); }
.reveal .answer {
  margin-top: 16px;
  display: none;
  font-size: 16px;
  color: var(--ink);
  padding-top: 16px;
  border-top: 1px solid var(--line-soft);
}
.reveal .answer.show { display: block; }

/* ---------- FOOTER ---------- */
footer {
  padding: 80px 0 60px;
  text-align: center;
}
footer .ornament { margin: 0 0 24px; }
footer p {
  font-style: italic;
  color: var(--ink-faded);
  font-size: 15px;
  margin-bottom: 8px;
}

/* ---------- WINDOW VISUALISATION (GBN / SR) ---------- */
.window-vis {
  display: flex;
  gap: 0;
  margin-top: 12px;
}
.window-vis .cell {
  width: 48px;
  height: 48px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-family: var(--mono);
  font-size: 14px;
  font-weight: 600;
  border: 1.5px solid var(--line);
  border-right: none;
  color: var(--paper);
}
.window-vis .cell:last-child {
  border-right: 1.5px solid var(--line);
}
.window-vis .cell.acked {
  background: var(--green);
  border-color: var(--green);
}
.window-vis .cell.sent {
  background: var(--rust);
  border-color: var(--rust);
}
.window-vis .cell.usable {
  background: var(--ochre);
  border-color: var(--ochre);
}
.window-vis .cell.blocked {
  background: var(--paper-darker);
  border-color: var(--line);
  color: var(--ink-ghost);
}

/* ---------- PROTOCOL TIMELINE ---------- */
.proto-timeline {
  margin: 32px 0;
  border-left: 3px solid var(--line);
  padding-left: 28px;
}
.proto-step {
  position: relative;
  margin-bottom: 28px;
}
.proto-step::before {
  content: '';
  position: absolute;
  left: -35px;
  top: 6px;
  width: 11px;
  height: 11px;
  border-radius: 50%;
  background: var(--rust);
  border: 2px solid var(--paper);
}
.proto-step:last-child { margin-bottom: 0; }
.proto-name {
  font-family: var(--mono);
  font-size: 14px;
  font-weight: 700;
  color: var(--rust);
  margin-bottom: 2px;
}
.proto-channel {
  font-family: var(--sans);
  font-size: 12px;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--ink-ghost);
  margin-bottom: 6px;
}
.proto-step p {
  font-size: 15px;
  color: var(--ink-soft);
  margin-bottom: 0;
}

/* ---------- ANIMATIONS ---------- */
@keyframes fadeUp {
  from { opacity: 0; transform: translateY(12px); }
  to   { opacity: 1; transform: translateY(0); }
}

/* ---------- RESPONSIVE ---------- */
@media (max-width: 768px) {
  body { font-size: 17px; }
  .container,
  .container-wide,
  .container.wide { padding: 0 20px; }
  .hero { padding: 60px 0 40px; }
  .hero h1 { font-size: 42px !important; }
  .hero .learn-box ul,
  .hero .what-youll-learn ul { grid-template-columns: 1fr; }
  .toc { grid-template-columns: 1fr; }
  section { padding: 60px 0; }
  h2 { font-size: 30px !important; }
  h3 { font-size: 22px; }
  .callout, .box, .info-box, .quiz, .stepper, .slider-box { padding: 20px; }
  figure { padding: 16px; overflow-x: auto; }
  pre { font-size: 12px; }
  .stats { grid-template-columns: 1fr; }
  .sim-controls { grid-template-columns: 1fr; }
  .sim-results {
    grid-template-columns: 1fr;
    max-width: none;
  }
  p.lead::first-letter,
  .dropcap::first-letter { font-size: 4em; }
  .subpage-list { grid-template-columns: 1fr; }
  .window-vis .cell { width: 36px; height: 36px; font-size: 12px; }
  .window-vis { overflow-x: auto; }
  figure:has(.packet) { padding: 0; }
  .packet .cell { min-height: 44px; padding: 6px 3px; }
}

/* ---------- PAGE NAVIGATION (prev/next) ---------- */
.page-nav {
  border-top: 1px solid var(--line);
  background: var(--paper-dark);
  padding: 40px 0 56px;
  display: flex;
  flex-wrap: wrap;
  align-items: stretch;
  gap: 14px 18px;
  justify-content: space-between;
}
.page-nav > .container {
  display: flex;
  flex-wrap: wrap;
  align-items: stretch;
  gap: 14px 18px;
  justify-content: space-between;
  flex: 1 1 100%;
  min-width: 0;
}
.page-nav .container > a,
.page-nav > a {
  display: flex;
  flex-direction: row;
  align-items: baseline;
  gap: 14px 18px;
  flex: 1 1 300px;
  min-width: 0;
  max-width: 100%;
  padding: 16px 20px;
  border: 1px solid var(--line);
  border-radius: 3px;
  text-decoration: none;
  color: inherit;
  transition: border-color 0.15s, background 0.15s, box-shadow 0.15s;
}
.page-nav a.next {
  flex-direction: row-reverse;
}
.page-nav .container > a:only-child,
.page-nav > a:only-child {
  flex: 0 1 min(100%, 34rem);
}
.page-nav .container > a:only-child.next,
.page-nav > a:only-child.next {
  margin-left: auto;
}
.page-nav .container > a:only-child.prev,
.page-nav > a:only-child.prev {
  margin-right: auto;
}
.page-nav .container > a:hover,
.page-nav > a:hover {
  border-color: var(--rust);
  background: var(--paper);
  box-shadow: 0 1px 0 rgba(26, 22, 18, 0.04);
}
.page-nav .nav-label {
  flex: 0 0 auto;
  font-family: var(--mono);
  font-size: 11px;
  letter-spacing: 0.15em;
  text-transform: uppercase;
  color: var(--ink-ghost);
}
.page-nav .nav-title {
  flex: 1;
  min-width: 0;
  font-family: var(--serif);
  font-size: 18px;
  font-weight: 500;
  line-height: 1.35;
  color: var(--ink);
}
.page-nav a.next .nav-title {
  text-align: right;
}
@media (max-width: 768px) {
  .page-nav { padding: 28px 0 40px; }
  .page-nav > .container { flex-direction: column; }
  .page-nav .container > a,
  .page-nav > a {
    flex: 1 1 auto;
    width: 100%;
    max-width: none;
    flex-direction: column;
    align-items: flex-start;
    gap: 6px;
  }
  .page-nav .container > a:only-child,
  .page-nav > a:only-child {
    margin-left: 0;
    margin-right: 0;
  }
  .page-nav a.next {
    align-items: flex-end;
  }
  .page-nav a.next .nav-title {
    text-align: right;
  }
}

/* ---------- CHAPTER TOC (mini-innholdsfortegnelse) ---------- */
.chapter-toc {
  padding: 28px 0;
  border-bottom: 1px solid var(--line);
  background: var(--paper-dark);
}
.chapter-toc .chapter-toc-list {
  display: flex;
  gap: 32px;
  list-style: none;
  margin: 0;
  padding: 0;
  flex-wrap: wrap;
}
.chapter-toc .chapter-toc-list li {
  margin: 0;
  display: flex;
  align-items: baseline;
  gap: 10px;
}
.chapter-toc .chapter-toc-list .toc-num {
  font-family: var(--mono);
  font-size: 12px;
  color: var(--ink-ghost);
  font-weight: 600;
}
.chapter-toc .chapter-toc-list a {
  font-family: var(--sans);
  font-size: 15px;
  font-weight: 500;
  color: var(--ink-soft);
  text-decoration: none;
  transition: color 0.15s;
}
.chapter-toc .chapter-toc-list a:hover {
  color: var(--rust);
}
@media (max-width: 768px) {
  .chapter-toc .chapter-toc-list {
    flex-direction: column;
    gap: 12px;
  }
}

/* ---------- SUBPAGE LIST (chapter overview) ---------- */
.subpage-list {
  display: grid;
  grid-template-columns: 1fr;
  gap: 0;
}
.subpage-card {
  display: grid;
  grid-template-columns: 50px 1fr auto;
  align-items: center;
  gap: 20px;
  padding: 24px 0;
  border-bottom: 1px solid var(--line-soft);
  text-decoration: none;
  color: inherit;
  transition: background 0.15s, padding 0.15s;
}
.subpage-card:first-child {
  border-top: 1px solid var(--line-soft);
}
.subpage-card:hover {
  background: var(--paper-dark);
  padding-left: 16px;
  padding-right: 16px;
  margin-left: -16px;
  margin-right: -16px;
  border-radius: 4px;
}
.subpage-card .sp-icon {
  font-family: var(--mono);
  font-size: 13px;
  color: var(--rust);
  font-weight: 600;
}
.subpage-card .sp-info { min-width: 0; }
.subpage-card .sp-title {
  font-family: var(--serif);
  font-size: 20px;
  font-weight: 500;
  line-height: 1.3;
  margin-bottom: 4px;
}
.subpage-card .sp-desc {
  font-size: 14px;
  color: var(--ink-faded);
  font-style: italic;
  line-height: 1.45;
}
.subpage-card .sp-arrow {
  font-family: var(--mono);
  font-size: 18px;
  color: var(--ink-ghost);
  transition: color 0.15s, transform 0.15s;
}
.subpage-card:hover .sp-arrow {
  color: var(--rust);
  transform: translateX(4px);
}