/* =============================================================
   GOJIHA · The Subnetting Field Manual
   Aesthetic: Field Engineer's Manual / Technical Drafting Bureau
   ============================================================= */

:root {
  /* Paper & ink */
  --paper:        #f1ebdc;
  --paper-2:      #e8e1cf;
  --paper-3:      #ddd4be;
  --ink:          #161311;
  --ink-2:        #2a241f;
  --ink-soft:     #4a4138;
  --muted:        #7a7367;

  /* Accent ink */
  --vermilion:    #c54023;
  --vermilion-2:  #a8341d;
  --navy:         #1c2a44;
  --navy-2:       #0f1a30;
  --ochre:        #c89d4a;
  --ochre-2:      #b08840;
  --sage:         #6b7d5a;
  --lime:         #c4ff4d;

  /* Type */
  --serif-disp:   "Fraunces", "Times New Roman", serif;
  --serif-body:   "Newsreader", "Times New Roman", serif;
  --mono:         "JetBrains Mono", ui-monospace, "SF Mono", monospace;

  /* Rhythm */
  --measure:      66ch;
  --rule:         1px solid var(--ink);
  --gutter:       clamp(1.25rem, 3vw, 2.5rem);
}

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

html {
  -webkit-text-size-adjust: 100%;
  text-rendering: optimizeLegibility;
  scroll-behavior: smooth;
}

body {
  margin: 0;
  background: var(--paper);
  color: var(--ink);
  font-family: var(--serif-body);
  font-size: 18px;
  line-height: 1.6;
  font-feature-settings: "kern" 1, "liga" 1, "onum" 1, "pnum" 1;
  background-image:
    radial-gradient(1200px 600px at 100% 0%, rgba(196, 64, 35, 0.04), transparent 60%),
    radial-gradient(900px 500px at 0% 100%, rgba(28, 42, 68, 0.05), transparent 60%),
    url("data:image/svg+xml;utf8,<svg xmlns='http://www.w3.org/2000/svg' width='240' height='240'><filter id='n'><feTurbulence type='fractalNoise' baseFrequency='0.85' numOctaves='2' stitchTiles='stitch'/><feColorMatrix values='0 0 0 0 0.08  0 0 0 0 0.07  0 0 0 0 0.06  0 0 0 0.08 0'/></filter><rect width='100%25' height='100%25' filter='url(%23n)'/></svg>");
  background-size: auto, auto, 240px 240px;
  background-attachment: fixed, fixed, fixed;
}

::selection { background: var(--vermilion); color: var(--paper); }

img, svg { max-width: 100%; display: block; }

a {
  color: var(--ink);
  text-decoration: none;
  background-image: linear-gradient(transparent calc(100% - 1px), var(--vermilion) calc(100% - 1px));
  background-size: 0% 100%;
  background-repeat: no-repeat;
  transition: background-size 320ms ease;
}
a:hover, a:focus-visible { background-size: 100% 100%; }
a:focus-visible { outline: 2px solid var(--vermilion); outline-offset: 3px; border-radius: 1px; }

code, .mono {
  font-family: var(--mono);
  font-size: 0.88em;
  letter-spacing: -0.01em;
  color: var(--vermilion);
  background: rgba(196, 64, 35, 0.07);
  padding: 0.08em 0.34em;
  border-radius: 2px;
  font-feature-settings: "tnum" 1, "zero" 1;
}

em { font-style: italic; }

strong { font-weight: 600; color: var(--ink-2); }

abbr[title] { text-decoration: none; border-bottom: 1px dotted var(--muted); }

.skip-link {
  position: absolute; left: -9999px;
  background: var(--ink); color: var(--paper);
  padding: 0.5em 1em; z-index: 999;
}
.skip-link:focus { left: 1rem; top: 1rem; }

/* ---------- Ruler (top nav strip) ---------- */
.ruler {
  position: sticky;
  top: 0;
  z-index: 50;
  display: grid;
  grid-template-columns: auto 1fr auto;
  align-items: center;
  gap: 1.5rem;
  padding: 0.6rem clamp(1rem, 3vw, 2rem);
  background: color-mix(in srgb, var(--paper) 92%, transparent);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--ink);
  font-family: var(--mono);
  font-size: 11px;
  text-transform: uppercase;
  letter-spacing: 0.12em;
}
.ruler__brand { display: inline-flex; align-items: center; gap: 0.5rem; }
.ruler__mark { color: var(--vermilion); font-size: 14px; line-height: 1; transform: translateY(-1px); }
.ruler__imprint { font-weight: 700; letter-spacing: 0.2em; }
.ruler__sep, .ruler__issue { color: var(--ink-soft); }
.ruler__nav { display: flex; gap: 1.1rem; justify-content: center; flex-wrap: wrap; }
.ruler__nav a {
  background: none; padding: 0.2rem 0;
  border-bottom: 1px solid transparent;
  color: var(--ink-soft);
  transition: color 180ms, border-color 180ms;
}
.ruler__nav a:hover, .ruler__nav a:focus-visible {
  background: none; color: var(--ink); border-color: var(--vermilion);
}
.ruler__meta { display: inline-flex; align-items: center; gap: 0.5rem; }
.ruler__coord {
  display: inline-block; padding: 0.2rem 0.5rem;
  border: 1px solid var(--ink); border-radius: 2px;
  font-weight: 700; color: var(--vermilion);
  min-width: 3ch; text-align: center;
}

@media (max-width: 880px) {
  .ruler { grid-template-columns: 1fr auto; gap: 0.6rem; padding: 0.5rem 1rem; font-size: 10px; }
  .ruler__nav { display: none; }
  .ruler__brand { font-size: 10px; }
  .ruler__issue { display: none; }
}

/* ---------- Cover ---------- */
.cover {
  position: relative;
  min-height: calc(100vh - 46px);
  padding: clamp(2.5rem, 6vw, 6rem) var(--gutter) clamp(3rem, 8vw, 7rem);
  display: grid;
  grid-template-columns: minmax(0, 1.4fr) minmax(0, 0.6fr);
  gap: clamp(2rem, 5vw, 4rem);
  max-width: 1440px;
  margin: 0 auto;
  border-bottom: 2px solid var(--ink);
}

.cover__grid {
  position: absolute; inset: 0; pointer-events: none;
  color: var(--ink);
  padding: 1.5rem;
}
.cover__corner {
  position: absolute; width: 60px; height: 60px;
  color: var(--ink); opacity: 0.7;
}
.cover__corner--tl { top: 0; left: 0; }
.cover__corner--tr { top: 0; right: 0; }
.cover__corner--bl { bottom: 0; left: 0; }
.cover__corner--br { bottom: 0; right: 0; }

.cover__inner {
  position: relative;
  display: flex; flex-direction: column; justify-content: center;
  max-width: 32ch;
  animation: coverIn 900ms cubic-bezier(0.2, 0.7, 0.2, 1) both;
}
@keyframes coverIn {
  from { opacity: 0; transform: translateY(18px); }
  to   { opacity: 1; transform: translateY(0); }
}

.cover__meta {
  display: flex; flex-wrap: wrap; gap: 0.5rem;
  margin-bottom: 1.6rem;
  font-family: var(--mono);
  font-size: 11px;
  text-transform: uppercase;
  letter-spacing: 0.18em;
}
.cover__pill {
  padding: 0.3rem 0.6rem;
  border: 1px solid var(--ink);
  border-radius: 999px;
  background: var(--ink);
  color: var(--paper);
}
.cover__pill--ghost { background: transparent; color: var(--ink); }

.cover__title {
  font-family: var(--serif-disp);
  font-weight: 300;
  font-variation-settings: "opsz" 144, "SOFT" 30, "WONK" 0;
  line-height: 0.85;
  letter-spacing: -0.04em;
  margin: 0 0 1.4rem;
  font-size: clamp(4.5rem, 14vw, 13rem);
  color: var(--ink);
}
.cover__title-line { display: block; }
.cover__title-line--accent {
  font-style: italic;
  font-weight: 400;
  color: var(--vermilion);
  font-variation-settings: "opsz" 144, "SOFT" 100, "WONK" 1;
  margin-left: -0.04em;
}
.cover__title-line--accent em {
  font-style: italic;
  color: var(--ink);
  font-variation-settings: "opsz" 144, "SOFT" 0;
}

.cover__dek {
  font-family: var(--serif-body);
  font-size: clamp(1.05rem, 1.4vw, 1.3rem);
  line-height: 1.45;
  color: var(--ink-soft);
  max-width: 34ch;
  margin: 0 0 2rem;
  font-style: italic;
}
.cover__dek .ink { color: var(--ink); font-style: normal; font-weight: 500; }

.cover__rules {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 1rem;
  margin: 1.4rem 0 2.4rem;
  padding: 1rem 0;
  border-top: var(--rule);
  border-bottom: var(--rule);
  font-family: var(--mono);
}
.cover__rule { display: flex; flex-direction: column; gap: 0.25rem; }
.cover__rule-num {
  font-size: 1.4rem; font-weight: 700; color: var(--vermilion);
  font-feature-settings: "tnum" 1, "ss01" 1;
}
.cover__rule-lbl {
  font-size: 10px; text-transform: uppercase; letter-spacing: 0.15em;
  color: var(--ink-soft);
}

.cover__enter {
  display: inline-flex; align-items: center; gap: 0.8rem;
  padding: 0.9rem 1.4rem;
  background: var(--ink); color: var(--paper);
  border: 1px solid var(--ink);
  font-family: var(--mono); font-size: 12px; text-transform: uppercase;
  letter-spacing: 0.18em; align-self: flex-start;
  transition: background 220ms, color 220ms, transform 220ms;
  background-image: none;
}
.cover__enter svg { width: 36px; height: 12px; transition: transform 220ms; }
.cover__enter:hover { background: var(--vermilion); border-color: var(--vermilion); color: var(--paper); transform: translateY(-1px); }
.cover__enter:hover svg { transform: translateX(4px); }

.cover__toc {
  position: relative;
  padding: 1.6rem 1.4rem;
  border: 1px solid var(--ink);
  background: rgba(255, 255, 255, 0.18);
  align-self: center;
  animation: coverIn 900ms 200ms cubic-bezier(0.2, 0.7, 0.2, 1) both;
}
.cover__toc-title {
  font-family: var(--mono); font-size: 10px;
  text-transform: uppercase; letter-spacing: 0.2em;
  margin: 0 0 0.8rem; padding-bottom: 0.6rem;
  border-bottom: 1px solid var(--ink);
  color: var(--ink-soft);
}
.cover__toc-list { list-style: none; padding: 0; margin: 0; counter-reset: toc; }
.cover__toc-list li { counter-increment: toc; }
.cover__toc-list a {
  display: flex; align-items: baseline; justify-content: space-between;
  padding: 0.45rem 0;
  border-bottom: 1px dotted color-mix(in srgb, var(--ink) 30%, transparent);
  font-family: var(--serif-body);
  font-size: 0.95rem; color: var(--ink);
  background: none;
}
.cover__toc-list li:last-child a { border-bottom: none; }
.cover__toc-list a b {
  font-family: var(--serif-disp); font-style: italic; font-weight: 400;
  margin-right: 0.5rem; color: var(--vermilion);
}
.cover__toc-list a span {
  font-family: var(--mono); font-size: 10px;
  color: var(--ink-soft); letter-spacing: 0.1em;
}
.cover__toc-list a:hover, .cover__toc-list a:focus-visible {
  background: none; color: var(--vermilion);
}

.cover__seal {
  position: absolute; bottom: 1.5rem; left: 50%;
  transform: translateX(-50%);
  width: 130px; height: 130px;
  color: var(--vermilion);
  pointer-events: none;
  opacity: 0.85;
}

@media (max-width: 880px) {
  .cover {
    grid-template-columns: 1fr;
    min-height: auto;
    padding-top: 2rem;
  }
  .cover__seal { display: none; }
  .cover__rules { grid-template-columns: repeat(2, 1fr); }
}

/* ---------- Article common ---------- */
.article {
  position: relative;
  max-width: 1280px;
  margin: 0 auto;
  padding: clamp(4rem, 9vw, 8rem) var(--gutter);
  border-bottom: 1px solid color-mix(in srgb, var(--ink) 25%, transparent);
}
.article--alt { background: linear-gradient(180deg, transparent 0, rgba(28, 42, 68, 0.025) 50%, transparent 100%); }
.article--instrument {
  background: var(--ink); color: var(--paper);
  border-bottom: 1px solid var(--ink);
}
.article--instrument::before {
  content: ""; position: absolute; inset: 0;
  background-image: url("data:image/svg+xml;utf8,<svg xmlns='http://www.w3.org/2000/svg' width='240' height='240'><filter id='n'><feTurbulence type='fractalNoise' baseFrequency='0.9' numOctaves='2' stitchTiles='stitch'/><feColorMatrix values='0 0 0 0 1  0 0 0 0 0.95  0 0 0 0 0.85  0 0 0 0.06 0'/></filter><rect width='100%25' height='100%25' filter='url(%23n)'/></svg>");
  pointer-events: none; opacity: 0.5;
}
.article--instrument .article__title { color: var(--paper); }
.article--instrument .article__title em { color: var(--lime); }
.article--instrument .article__standfirst { color: color-mix(in srgb, var(--paper) 80%, transparent); }
.article--instrument .article__kicker { color: var(--lime); }
.article--instrument .article__num-roman { color: var(--lime); }
.article--practice { background: linear-gradient(180deg, var(--paper) 0, var(--paper-2) 100%); }

.article__head {
  display: grid;
  grid-template-columns: auto 1fr;
  gap: clamp(1.5rem, 4vw, 3rem);
  align-items: start;
  margin-bottom: clamp(2rem, 5vw, 4rem);
  padding-bottom: clamp(1.5rem, 3vw, 2.5rem);
  border-bottom: 2px solid var(--ink);
}
.article--instrument .article__head { border-bottom-color: var(--paper); }

.article__num {
  display: flex; flex-direction: column; align-items: flex-start;
  font-family: var(--serif-disp);
  line-height: 0.8;
  padding-top: 0.4rem;
}
.article__num-roman {
  font-style: italic; font-weight: 300; font-size: clamp(3.5rem, 7vw, 5.5rem);
  color: var(--vermilion);
  font-variation-settings: "opsz" 144;
}
.article__num-arabic {
  font-family: var(--mono); font-size: 12px;
  letter-spacing: 0.2em; color: var(--ink-soft);
  margin-top: 0.3rem;
}
.article--instrument .article__num-arabic { color: color-mix(in srgb, var(--paper) 60%, transparent); }

.article__kicker {
  font-family: var(--mono); font-size: 11px;
  text-transform: uppercase; letter-spacing: 0.2em;
  color: var(--vermilion);
  margin: 0 0 0.6rem;
}
.article__title {
  font-family: var(--serif-disp);
  font-weight: 300;
  font-size: clamp(2.5rem, 6vw, 5rem);
  line-height: 0.95;
  letter-spacing: -0.025em;
  margin: 0 0 1rem;
  font-variation-settings: "opsz" 144, "SOFT" 30;
}
.article__title em {
  font-style: italic; color: var(--vermilion);
  font-variation-settings: "opsz" 144, "SOFT" 100, "WONK" 1;
}
.article__standfirst {
  font-family: var(--serif-body);
  font-size: clamp(1.1rem, 1.5vw, 1.4rem);
  line-height: 1.45;
  font-style: italic;
  color: var(--ink-soft);
  margin: 0;
  max-width: 60ch;
}

.article__body {
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(0, 1fr);
  gap: clamp(2rem, 5vw, 4rem);
  align-items: start;
  position: relative;
}

.prose p {
  font-size: 1.075rem;
  line-height: 1.65;
  max-width: var(--measure);
  margin: 0 0 1.1rem;
  color: var(--ink-2);
}
.prose strong { color: var(--ink); }

.dropcap::first-letter,
.dropcap .dropcap__letter {
  font-family: var(--serif-disp);
  font-weight: 300;
  font-style: italic;
  font-size: 5.4em;
  line-height: 0.85;
  float: left;
  padding: 0.05em 0.12em 0 0;
  color: var(--vermilion);
  font-variation-settings: "opsz" 144, "SOFT" 100, "WONK" 1;
}

.prose--two-col {
  grid-column: 1 / -1;
  column-count: 2;
  column-gap: 2.5rem;
  column-rule: 1px solid color-mix(in srgb, var(--ink) 20%, transparent);
  max-width: 100%;
}
.prose--two-col p { max-width: none; }

.figure {
  margin: 0;
  padding: 1.6rem;
  border: 1px solid var(--ink);
  background: rgba(255, 255, 255, 0.25);
}
.article--instrument .figure {
  background: var(--paper);
  color: var(--ink);
  border-color: var(--paper);
}
.figure__caption {
  font-family: var(--mono);
  font-size: 11px;
  text-transform: uppercase;
  letter-spacing: 0.15em;
  color: var(--ink-soft);
  margin-bottom: 1.2rem;
  padding-bottom: 0.8rem;
  border-bottom: 1px dashed color-mix(in srgb, var(--ink) 30%, transparent);
}
.figure__num {
  color: var(--vermilion); font-weight: 700; margin-right: 0.6em;
}

.margin-note {
  grid-column: 1 / -1;
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(0, 1fr);
  gap: clamp(2rem, 5vw, 4rem);
  padding: 1.4rem 1.6rem;
  background: rgba(28, 42, 68, 0.04);
  border-left: 4px solid var(--navy);
  align-items: start;
  margin-top: 1rem;
}
.margin-note--alt { border-left-color: var(--vermilion); background: rgba(196, 64, 35, 0.05); }
.margin-note__label {
  font-family: var(--mono); font-size: 10px;
  text-transform: uppercase; letter-spacing: 0.2em;
  color: var(--vermilion); display: block; margin-bottom: 0.4rem;
}
.margin-note p {
  margin: 0; max-width: 56ch;
  font-size: 0.95rem; line-height: 1.55;
  grid-column: 2; color: var(--ink-soft);
}
@media (max-width: 880px) {
  .article__head { grid-template-columns: 1fr; gap: 1rem; }
  .article__body { grid-template-columns: 1fr; }
  .prose--two-col { column-count: 1; }
  .margin-note { grid-template-columns: 1fr; }
  .margin-note p { grid-column: 1; }
}

/* ---------- Bitfield (Article 01) ---------- */
.bitfield {
  display: grid;
  grid-template-columns: repeat(32, 1fr);
  gap: 3px;
  padding: 0.8rem;
  background: var(--ink);
  border-radius: 4px;
}
.bitfield__bit {
  aspect-ratio: 1 / 1;
  display: grid; place-items: center;
  font-family: var(--mono);
  font-size: 11px;
  font-weight: 600;
  color: var(--ink);
  background: var(--paper-2);
  border-radius: 2px;
  transition: transform 160ms, background 160ms, color 160ms;
  position: relative;
  user-select: none;
}
.bitfield__bit--set { background: var(--vermilion); color: var(--paper); }
.bitfield__bit--editable { cursor: pointer; }
.bitfield__bit--editable:hover { transform: translateY(-2px); box-shadow: 0 3px 0 var(--vermilion-2); }
.bitfield__octet-sep {
  width: 2px; align-self: stretch;
  background: var(--paper);
  border-radius: 1px;
}
.bitfield__legend {
  display: flex; flex-wrap: wrap; gap: 1.2rem;
  margin-top: 0.8rem; font-family: var(--mono); font-size: 11px;
  color: var(--ink-soft); text-transform: uppercase; letter-spacing: 0.1em;
}
.bitfield__legend .dot { display: inline-block; width: 10px; height: 10px; border-radius: 2px; margin-right: 0.4em; vertical-align: -1px; }
.dot--ink { background: var(--vermilion); }
.dot--paper { background: var(--paper-2); border: 1px solid var(--ink-soft); }
.dot--vermilion { background: var(--vermilion); border: 1px solid var(--ink-soft); }
@media (max-width: 600px) {
  .bitfield__bit { font-size: 8px; }
}

/* ---------- Mask instrument (Article 02) ---------- */
.mask-instrument { display: grid; gap: 1.4rem; }
.mask-instrument__display {
  display: grid; gap: 0.6rem;
  padding: 1.2rem 1.4rem;
  border: 1px solid var(--ink);
  background: rgba(255, 255, 255, 0.3);
  font-family: var(--mono);
  font-size: 0.95rem;
}
.mask-instrument__row {
  display: grid; grid-template-columns: 18ch 1fr;
  gap: 1rem; align-items: baseline;
  padding: 0.4rem 0;
  border-bottom: 1px dotted color-mix(in srgb, var(--ink) 25%, transparent);
}
.mask-instrument__row:last-child { border-bottom: none; }
.mask-instrument__row--split {
  grid-template-columns: 1fr;
  grid-template-columns: repeat(4, 1fr);
  gap: 1rem;
  margin-top: 0.6rem; padding-top: 0.8rem;
  border-top: 1px solid var(--ink);
}
.mask-instrument__lbl {
  text-transform: uppercase; letter-spacing: 0.12em;
  font-size: 10px; color: var(--ink-soft);
}
.mask-instrument__val { font-weight: 600; color: var(--ink); }
.mask-instrument__val--big {
  font-size: 1.4rem; color: var(--vermilion);
  font-feature-settings: "tnum" 1;
}
.mask-instrument__val--mono {
  font-size: 0.75rem; letter-spacing: 0.05em;
  word-break: break-all;
}
.mask-instrument__dial {
  position: relative; padding: 1rem 0;
}
.mask-instrument__dial input[type=range] {
  -webkit-appearance: none; appearance: none;
  width: 100%; height: 14px;
  background: transparent; cursor: pointer;
}
.mask-instrument__dial input[type=range]::-webkit-slider-runnable-track {
  height: 4px; background: var(--ink); border-radius: 2px;
}
.mask-instrument__dial input[type=range]::-moz-range-track {
  height: 4px; background: var(--ink); border-radius: 2px;
}
.mask-instrument__dial input[type=range]::-webkit-slider-thumb {
  -webkit-appearance: none; appearance: none;
  width: 22px; height: 22px; border-radius: 50%;
  background: var(--vermilion); border: 3px solid var(--paper);
  box-shadow: 0 0 0 1px var(--ink);
  margin-top: -9px;
  transition: transform 160ms;
}
.mask-instrument__dial input[type=range]::-moz-range-thumb {
  width: 22px; height: 22px; border-radius: 50%;
  background: var(--vermilion); border: 3px solid var(--paper);
  box-shadow: 0 0 0 1px var(--ink);
  transition: transform 160ms;
}
.mask-instrument__dial input[type=range]:hover::-webkit-slider-thumb { transform: scale(1.1); }
.mask-instrument__dial input[type=range]:hover::-moz-range-thumb { transform: scale(1.1); }
.mask-instrument__dial input[type=range]:focus-visible { outline: none; }
.mask-instrument__dial input[type=range]:focus-visible::-webkit-slider-thumb {
  box-shadow: 0 0 0 3px color-mix(in srgb, var(--vermilion) 40%, transparent);
}
.mask-instrument__ticks {
  display: grid; grid-template-columns: repeat(33, 1fr);
  margin-top: 0.4rem; height: 18px;
}
.mask-instrument__ticks span {
  font-family: var(--mono); font-size: 9px;
  color: var(--ink-soft); text-align: center;
  position: relative;
}
.mask-instrument__ticks span::before {
  content: ""; display: block;
  width: 1px; height: 6px; background: var(--ink-soft);
  margin: 0 auto 2px;
}
.mask-instrument__ticks span:nth-child(9n+1) { color: var(--vermilion); font-weight: 700; }

/* ---------- Calculator (Article 03 - dark) ---------- */
.calculator {
  position: relative; z-index: 1;
  display: grid; gap: 1.5rem;
  padding: clamp(1.6rem, 3vw, 2.4rem);
  background: var(--ink-2);
  color: var(--paper);
  border: 1px solid var(--paper);
  box-shadow:
    inset 0 0 0 6px var(--ink-2),
    inset 0 0 0 7px color-mix(in srgb, var(--paper) 30%, transparent),
    0 30px 80px -20px rgba(0,0,0,0.5);
}
.calculator__inputs {
  display: grid;
  grid-template-columns: 1fr auto auto;
  gap: 1rem; align-items: end;
  padding-bottom: 1.2rem;
  border-bottom: 1px solid color-mix(in srgb, var(--paper) 25%, transparent);
}
.calculator__field { display: grid; gap: 0.4rem; }
.calculator__field--narrow { width: 8ch; }
.calculator__field-lbl {
  font-family: var(--mono); font-size: 10px;
  text-transform: uppercase; letter-spacing: 0.18em;
  color: var(--lime);
}
.calculator__field input {
  font-family: var(--mono); font-size: 1.6rem;
  background: transparent; color: var(--paper);
  border: none; border-bottom: 1px solid var(--paper);
  padding: 0.3rem 0; outline: none; width: 100%;
  font-feature-settings: "tnum" 1;
  letter-spacing: 0.05em;
}
.calculator__field input:focus { border-bottom-color: var(--lime); }
.calculator__field--narrow input { color: var(--lime); }
.calculator__btn {
  display: inline-flex; align-items: center; gap: 0.5rem;
  padding: 0.7rem 1rem;
  background: var(--vermilion); color: var(--paper);
  border: 1px solid var(--vermilion);
  font-family: var(--mono); font-size: 11px;
  text-transform: uppercase; letter-spacing: 0.15em;
  cursor: pointer; transition: background 200ms;
}
.calculator__btn:hover { background: var(--vermilion-2); }
.calculator__btn svg { width: 18px; height: 18px; }

.calculator__panel {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 1px;
  background: color-mix(in srgb, var(--paper) 25%, transparent);
  border: 1px solid color-mix(in srgb, var(--paper) 25%, transparent);
}
.calc-cell {
  display: grid; grid-template-rows: auto 1fr; gap: 0.3rem;
  padding: 1rem 1.1rem; background: var(--ink-2);
  min-height: 5.5rem;
}
.calc-cell__lbl {
  font-family: var(--mono); font-size: 9px;
  text-transform: uppercase; letter-spacing: 0.18em;
  color: color-mix(in srgb, var(--paper) 55%, transparent);
}
.calc-cell__val {
  font-family: var(--mono); font-size: 1.05rem;
  color: var(--paper); font-weight: 500;
  font-feature-settings: "tnum" 1;
}
.calc-cell--accent .calc-cell__val { color: var(--lime); }
.calc-cell--vermilion .calc-cell__val { color: var(--vermilion); }
.calc-cell--full { grid-column: 1 / -1; }
.calc-cell--full .calc-cell__val { font-size: 1.2rem; }
.calc-cell--full .calc-cell__val em { color: var(--lime); font-style: normal; }

.calculator__binary {
  display: grid; gap: 0.5rem;
  padding-top: 1rem;
  border-top: 1px solid color-mix(in srgb, var(--paper) 25%, transparent);
}
.calc-binary-row {
  display: grid; grid-template-columns: 8ch 1fr;
  gap: 1rem; align-items: center;
  font-family: var(--mono); font-size: 0.78rem;
  letter-spacing: 0.05em;
}
.calc-binary-row__lbl { color: color-mix(in srgb, var(--paper) 55%, transparent); text-transform: uppercase; font-size: 10px; letter-spacing: 0.18em; }
.calc-binary-row__val { color: var(--paper); word-break: break-all; }
.calc-binary-row__val b { color: var(--lime); }
.calc-binary-row__val u { color: var(--vermilion); text-decoration: none; border-bottom: 1px solid var(--vermilion); padding-bottom: 1px; }

@media (max-width: 720px) {
  .calculator__inputs { grid-template-columns: 1fr 1fr; }
  .calculator__btn { grid-column: 1 / -1; justify-content: center; }
  .calculator__panel { grid-template-columns: 1fr; }
  .calculator__field input { font-size: 1.3rem; }
}

/* ---------- Classes (Article 04) ---------- */
.classes {
  grid-column: 1 / -1;
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 1rem;
}
.classes__card {
  display: grid; gap: 1rem;
  padding: 1.4rem;
  background: var(--paper);
  border: 1px solid var(--ink);
  position: relative;
  overflow: hidden;
  transition: transform 240ms, box-shadow 240ms;
}
.classes__card::before {
  content: ""; position: absolute; top: 0; left: 0; right: 0; height: 4px;
}
.classes__card--a::before { background: var(--vermilion); }
.classes__card--b::before { background: var(--navy); }
.classes__card--c::before { background: var(--sage); }
.classes__card--d::before { background: var(--ochre); }
.classes__card--e::before { background: var(--ink-soft); }
.classes__card:hover { transform: translateY(-3px); box-shadow: 0 12px 24px -10px rgba(0,0,0,0.2); }
.classes__card-head { display: flex; align-items: baseline; justify-content: space-between; }
.classes__letter {
  font-family: var(--serif-disp);
  font-weight: 300; font-style: italic;
  font-size: 4.5rem; line-height: 0.85;
  color: var(--ink);
  font-variation-settings: "opsz" 144, "SOFT" 50, "WONK" 1;
}
.classes__card--a .classes__letter { color: var(--vermilion); }
.classes__card--b .classes__letter { color: var(--navy); }
.classes__card--c .classes__letter { color: var(--sage); }
.classes__card--d .classes__letter { color: var(--ochre); }
.classes__card--e .classes__letter { color: var(--ink-soft); }
.classes__bits {
  font-family: var(--mono); font-size: 11px;
  letter-spacing: 0.05em; color: var(--ink-soft);
}
.classes__bits i {
  display: inline-block; width: 0.7em; height: 0.7em;
  background: currentColor; border-radius: 50%;
  margin: 0 0.5px 0 0; vertical-align: 1px; opacity: 0.85;
}
.classes__data {
  margin: 0; display: grid; grid-template-columns: 1fr; gap: 0.4rem;
  font-size: 0.92rem;
  border-top: 1px solid color-mix(in srgb, var(--ink) 20%, transparent);
  padding-top: 0.8rem;
}
.classes__data div { display: grid; grid-template-columns: 9.5ch 1fr; gap: 0.5rem; align-items: baseline; }
.classes__data dt {
  font-family: var(--mono); font-size: 9px;
  text-transform: uppercase; letter-spacing: 0.15em;
  color: var(--ink-soft);
}
.classes__data dd { margin: 0; font-family: var(--mono); font-size: 0.85rem; color: var(--ink); }

/* ---------- Splitter (Article 05) ---------- */
.figure--split { grid-column: 1 / -1; }
.splitter { display: grid; gap: 1.2rem; }
.splitter__controls {
  display: grid; grid-template-columns: 1fr 1fr; gap: 1.4rem;
  align-items: end; padding-bottom: 1rem;
  border-bottom: 1px dashed color-mix(in srgb, var(--ink) 25%, transparent);
}
.splitter__controls label { display: grid; gap: 0.4rem; }
.splitter__controls > label:nth-child(2) {
  grid-template-columns: 1fr 4ch;
  display: grid; gap: 0.4rem 1rem;
  align-items: center;
}
.splitter__controls span {
  font-family: var(--mono); font-size: 10px;
  text-transform: uppercase; letter-spacing: 0.18em;
  color: var(--ink-soft);
}
.splitter__controls input[type=text] {
  font-family: var(--mono); font-size: 1.1rem;
  background: transparent; color: var(--ink);
  border: none; border-bottom: 1px solid var(--ink);
  padding: 0.3rem 0; outline: none; width: 100%;
}
.splitter__controls input[type=text]:focus { border-bottom-color: var(--vermilion); }
.splitter__controls input[type=range] {
  grid-column: 1 / 2;
  -webkit-appearance: none; appearance: none;
  width: 100%; height: 14px; background: transparent;
}
.splitter__controls input[type=range]::-webkit-slider-runnable-track { height: 3px; background: var(--ink); }
.splitter__controls input[type=range]::-moz-range-track { height: 3px; background: var(--ink); }
.splitter__controls input[type=range]::-webkit-slider-thumb {
  -webkit-appearance: none; appearance: none;
  width: 18px; height: 18px; border-radius: 50%;
  background: var(--vermilion); border: 2px solid var(--paper);
  box-shadow: 0 0 0 1px var(--ink); margin-top: -7px;
}
.splitter__controls input[type=range]::-moz-range-thumb {
  width: 18px; height: 18px; border-radius: 50%;
  background: var(--vermilion); border: 2px solid var(--paper);
  box-shadow: 0 0 0 1px var(--ink);
}
.splitter__controls output {
  grid-column: 2 / 3;
  font-family: var(--mono); font-size: 1.4rem;
  font-weight: 700; color: var(--vermilion);
  font-feature-settings: "tnum" 1;
}
.splitter__summary {
  font-family: var(--mono); font-size: 0.85rem;
  color: var(--ink-soft);
  letter-spacing: 0.02em;
}
.splitter__summary b { color: var(--vermilion); font-weight: 700; }
.splitter__bar {
  display: flex; height: 36px;
  border: 1px solid var(--ink);
  overflow: hidden;
  background: var(--paper-2);
}
.splitter__bar > div {
  flex: 1; border-right: 1px solid var(--ink);
  background: color-mix(in srgb, var(--vermilion) 12%, var(--paper-2));
  transition: background 280ms;
}
.splitter__bar > div:nth-child(even) { background: color-mix(in srgb, var(--navy) 10%, var(--paper-2)); }
.splitter__bar > div:last-child { border-right: none; }
.splitter__bar > div:hover { background: var(--vermilion); }
.splitter__list {
  list-style: none; margin: 0; padding: 0;
  display: grid; gap: 0.4rem;
  font-family: var(--mono); font-size: 0.85rem;
  max-height: 320px; overflow: auto;
  border: 1px solid color-mix(in srgb, var(--ink) 25%, transparent);
  padding: 0.6rem;
  background: rgba(255,255,255,0.3);
}
.splitter__list li {
  display: grid; grid-template-columns: 4ch 1fr auto;
  gap: 0.8rem; padding: 0.25rem 0.4rem;
  border-bottom: 1px dotted color-mix(in srgb, var(--ink) 20%, transparent);
}
.splitter__list li:last-child { border-bottom: none; }
.splitter__list li span:first-child { color: var(--ink-soft); }
.splitter__list li span:nth-child(2) { color: var(--ink); font-weight: 500; }
.splitter__list li span:last-child { color: var(--vermilion); font-weight: 700; }

@media (max-width: 720px) {
  .splitter__controls { grid-template-columns: 1fr; gap: 1rem; }
  .splitter__list li { grid-template-columns: 3ch 1fr; }
  .splitter__list li span:last-child { grid-column: 1 / -1; padding-left: 3ch; color: var(--ink-soft); font-weight: 400; font-size: 0.75rem; }
}

/* ---------- Cheatsheet (Article 06) ---------- */
.cheatsheet { grid-column: 1 / -1; }
.cheatsheet__table {
  width: 100%; border-collapse: collapse;
  font-family: var(--mono); font-size: 0.86rem;
  background: var(--paper);
}
.cheatsheet__table thead th {
  text-align: left;
  padding: 0.8rem 0.7rem;
  border-bottom: 2px solid var(--ink);
  border-top: 1px solid var(--ink);
  font-size: 10px;
  text-transform: uppercase; letter-spacing: 0.18em;
  color: var(--ink-soft);
  background: var(--paper-2);
}
.cheatsheet__table th.num, .cheatsheet__table td.num { text-align: right; font-feature-settings: "tnum" 1; }
.cheatsheet__table tbody tr {
  border-bottom: 1px solid color-mix(in srgb, var(--ink) 15%, transparent);
  transition: background 180ms;
}
.cheatsheet__table tbody tr:hover { background: rgba(196, 64, 35, 0.05); }
.cheatsheet__table tbody td {
  padding: 0.55rem 0.7rem; vertical-align: baseline;
}
.cheatsheet__table td:first-child { font-weight: 700; color: var(--vermilion); }
.cheatsheet__table td .notable { color: var(--ink-soft); font-style: italic; }

.cheatsheet__table tbody tr td .bar {
  display: inline-block; height: 6px; width: calc(var(--w, 0) * 1%);
  background: var(--vermilion);
  vertical-align: middle; margin-right: 0.6em; border-radius: 1px;
  opacity: 0.85;
}

@media (max-width: 720px) {
  .cheatsheet { overflow-x: auto; }
  .cheatsheet__table { min-width: 640px; }
}

/* ---------- Quiz (Article 07) ---------- */
.quiz {
  grid-column: 1 / -1;
  display: grid; gap: 1.5rem;
  padding: clamp(1.6rem, 3vw, 2.4rem);
  border: 2px solid var(--ink);
  background: var(--paper);
  position: relative;
}
.quiz::after {
  content: "QUIZ"; position: absolute; top: -0.8em; left: 1.5rem;
  background: var(--vermilion); color: var(--paper);
  padding: 0.2em 0.8em;
  font-family: var(--mono); font-size: 12px;
  letter-spacing: 0.25em; font-weight: 700;
}
.quiz__head {
  display: grid; grid-template-columns: 1fr auto auto;
  gap: 1rem; align-items: center;
  padding-bottom: 1rem;
  border-bottom: 1px solid color-mix(in srgb, var(--ink) 25%, transparent);
  font-family: var(--mono); font-size: 0.85rem;
}
.quiz__progress { display: flex; flex-direction: column; gap: 0.2rem; }
.quiz__progress-lbl {
  text-transform: uppercase; letter-spacing: 0.18em;
  font-size: 10px; color: var(--ink-soft);
}
.quiz__progress-num { font-weight: 700; color: var(--vermilion); font-size: 1.1rem; }
.quiz__score { font-weight: 700; color: var(--ink); }
.quiz__reset {
  background: transparent; border: 1px solid var(--ink);
  padding: 0.5rem 0.9rem; font-family: var(--mono); font-size: 11px;
  text-transform: uppercase; letter-spacing: 0.15em;
  cursor: pointer; transition: background 180ms, color 180ms;
}
.quiz__reset:hover { background: var(--ink); color: var(--paper); }

.quiz__body { display: grid; gap: 1.2rem; }
.quiz__q {
  font-family: var(--serif-disp);
  font-weight: 300; font-size: clamp(1.4rem, 2.4vw, 1.9rem);
  line-height: 1.2; margin: 0;
  color: var(--ink);
  font-variation-settings: "opsz" 144, "SOFT" 50;
}
.quiz__q code, .quiz__q .mono {
  font-size: 0.7em; vertical-align: middle;
  background: var(--ink); color: var(--lime);
  padding: 0.15em 0.5em;
}
.quiz__choices {
  display: grid; gap: 0.6rem;
  list-style: none; padding: 0; margin: 0;
}
.quiz__choice {
  display: grid; grid-template-columns: 2.4ch 1fr;
  gap: 0.8rem; align-items: center;
  padding: 0.9rem 1.1rem;
  border: 1px solid var(--ink);
  background: var(--paper);
  font-family: var(--mono); font-size: 0.95rem;
  cursor: pointer; text-align: left;
  transition: background 180ms, color 180ms, transform 160ms;
  width: 100%;
}
.quiz__choice__key {
  font-weight: 700; color: var(--ink-soft);
  border-right: 1px solid color-mix(in srgb, var(--ink) 30%, transparent);
  padding-right: 0.6rem;
}
.quiz__choice:hover { background: var(--ink); color: var(--paper); }
.quiz__choice:hover .quiz__choice__key { color: var(--lime); border-color: color-mix(in srgb, var(--paper) 40%, transparent); }
.quiz__choice--picked { background: var(--ink); color: var(--paper); }
.quiz__choice--picked .quiz__choice__key { color: var(--lime); border-color: color-mix(in srgb, var(--paper) 40%, transparent); }
.quiz__choice--correct { background: var(--sage); color: var(--paper); border-color: var(--sage); }
.quiz__choice--correct .quiz__choice__key { color: var(--paper); border-color: color-mix(in srgb, var(--paper) 50%, transparent); }
.quiz__choice--wrong { background: var(--vermilion); color: var(--paper); border-color: var(--vermilion); }
.quiz__choice--wrong .quiz__choice__key { color: var(--paper); border-color: color-mix(in srgb, var(--paper) 50%, transparent); }
.quiz__choice:disabled { cursor: default; }

.quiz__feedback {
  padding: 0.9rem 1.1rem;
  font-family: var(--mono); font-size: 0.85rem;
  border-left: 4px solid var(--vermilion);
  background: rgba(196, 64, 35, 0.05);
  color: var(--ink);
}
.quiz__feedback--ok { border-left-color: var(--sage); background: rgba(107, 125, 90, 0.08); }
.quiz__feedback b { color: var(--vermilion); }
.quiz__feedback--ok b { color: var(--sage); }

.quiz__actions { display: flex; justify-content: space-between; gap: 1rem; }
.quiz__btn {
  padding: 0.7rem 1.2rem;
  background: var(--ink); color: var(--paper);
  border: 1px solid var(--ink);
  font-family: var(--mono); font-size: 11px;
  text-transform: uppercase; letter-spacing: 0.15em;
  cursor: pointer; transition: background 180ms;
}
.quiz__btn:hover { background: var(--vermilion); border-color: var(--vermilion); }
.quiz__btn--ghost { background: transparent; color: var(--ink); }
.quiz__btn--ghost:hover { background: var(--ink); color: var(--paper); }

.quiz__final {
  display: grid; gap: 1rem; padding: 2rem;
  text-align: center;
  border: 1px solid var(--ink);
  background: var(--paper-2);
}
.quiz__final-score {
  font-family: var(--serif-disp); font-style: italic; font-weight: 300;
  font-size: clamp(3rem, 8vw, 5.5rem); color: var(--vermilion);
  font-variation-settings: "opsz" 144, "SOFT" 100, "WONK" 1;
  line-height: 1;
}
.quiz__final-msg {
  font-family: var(--serif-disp); font-style: italic;
  font-size: 1.4rem; color: var(--ink); margin: 0;
  font-variation-settings: "opsz" 144, "SOFT" 50;
}

/* ---------- Colophon ---------- */
.colophon {
  background: var(--ink);
  color: var(--paper);
  padding: clamp(3rem, 6vw, 5rem) var(--gutter) 0;
  position: relative;
  background-image: url("data:image/svg+xml;utf8,<svg xmlns='http://www.w3.org/2000/svg' width='240' height='240'><filter id='n'><feTurbulence type='fractalNoise' baseFrequency='0.85' numOctaves='2' stitchTiles='stitch'/><feColorMatrix values='0 0 0 0 1  0 0 0 0 0.95  0 0 0 0 0.85  0 0 0 0.04 0'/></filter><rect width='100%25' height='100%25' filter='url(%23n)'/></svg>");
}
.colophon__inner {
  max-width: 1280px; margin: 0 auto;
  display: grid; grid-template-columns: repeat(3, 1fr);
  gap: clamp(2rem, 4vw, 3rem);
  padding-bottom: 3rem;
}
.colophon__h {
  font-family: var(--mono); font-size: 11px;
  text-transform: uppercase; letter-spacing: 0.2em;
  color: var(--lime); margin: 0 0 1rem;
  padding-bottom: 0.5rem; border-bottom: 1px solid color-mix(in srgb, var(--paper) 25%, transparent);
}
.colophon__col p { font-size: 0.95rem; line-height: 1.6; color: color-mix(in srgb, var(--paper) 80%, transparent); margin: 0; }
.colophon__col a { color: var(--paper); background-image: linear-gradient(transparent calc(100% - 1px), var(--lime) calc(100% - 1px)); }
.colophon__col a:hover, .colophon__col a:focus-visible { color: var(--lime); }
.colophon__refs { list-style: none; padding: 0; margin: 0; display: grid; gap: 0.5rem; font-family: var(--mono); font-size: 0.85rem; }
.colophon__rule {
  display: grid; grid-template-columns: 1fr 1fr 1fr;
  align-items: center; text-align: center;
  padding: 1.2rem 0;
  border-top: 1px solid color-mix(in srgb, var(--paper) 25%, transparent);
  font-family: var(--mono); font-size: 10px;
  text-transform: uppercase; letter-spacing: 0.3em;
  color: color-mix(in srgb, var(--paper) 60%, transparent);
}
.colophon__rule span:last-child { color: var(--vermilion); }
@media (max-width: 720px) {
  .colophon__inner { grid-template-columns: 1fr; }
}

/* ---------- Print ---------- */
@media print {
  .ruler, .cover__corner, .cover__seal, .calculator__btn { display: none; }
  body { background: white; }
  .article { page-break-inside: avoid; }
}