:root {
  --paper: #14110d;
  --paper-dark: #1c1813;
  --ink: #f0e9d8;
  --ink-soft: #b8b0a0;
  --ink-faint: #7a7268;
  --rule: #3a342a;
  --rule-soft: #2a2520;
  --grid: #f0e9d8;
  --grid-soft: #2e2820;
  --accent: #e07b5a;       /* warm terracotta */
  --accent-2: #6db096;     /* sage green */
  --accent-3: #e6b04a;     /* mustard gold */
  --highlight: #5a4a18;    /* dim amber */
  --formula-bg: #221d16;
  --code-bg: #0a0807;
  --code-fg: #f0e9d8;
  --display-font: 'Fraunces', Georgia, serif;
  --body-font: 'Inter', -apple-system, sans-serif;
  --mono: 'JetBrains Mono', 'Courier New', monospace;
}
* { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; }
body {
  font-family: var(--body-font);
  background: var(--paper);
  color: var(--ink);
  line-height: 1.6;
  background-image:
    radial-gradient(circle at 20% 30%, rgba(224,123,90,0.06) 0, transparent 50%),
    radial-gradient(circle at 80% 70%, rgba(109,176,150,0.05) 0, transparent 50%),
    repeating-linear-gradient(0deg, transparent 0, transparent 31px, rgba(240,233,216,0.025) 31px, rgba(240,233,216,0.025) 32px);
}

/* ====== HERO ====== */
.hero {
  min-height: 92vh;
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  padding: 40px 6vw 60px;
  border-bottom: 2px solid var(--ink);
  position: relative;
  overflow: hidden;
}
.hero::before {
  content: "";
  position: absolute;
  inset: 0;
  background-image:
    linear-gradient(var(--grid-soft) 1px, transparent 1px),
    linear-gradient(90deg, var(--grid-soft) 1px, transparent 1px);
  background-size: 80px 80px;
  opacity: 0.4;
  pointer-events: none;
  z-index: 0;
}
.hero-top, .hero-mid, .hero-bot {
  position: relative;
  z-index: 1;
}
.hero-top {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  font-family: var(--mono);
  font-size: 11px;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--ink-soft);
}
.hero-top .meta-block { max-width: 220px; }
.hero-top .meta-block strong { color: var(--ink); display: block; font-weight: 700; }
.hero-mid {
  flex: 1;
  display: flex;
  align-items: center;
  padding: 60px 0;
}
.hero-title {
  font-family: var(--display-font);
  font-weight: 900;
  font-size: clamp(60px, 13vw, 220px);
  line-height: 0.85;
  letter-spacing: -0.04em;
  font-variation-settings: "opsz" 144;
}
.hero-title .word { display: block; }
.hero-title .word-2 {
  font-style: italic;
  color: var(--accent);
  font-weight: 400;
  padding-left: 0.4em;
}
.hero-title .word-3 {
  -webkit-text-stroke: 2px var(--ink);
  color: transparent;
  padding-left: 1.2em;
}
.hero-bot {
  display: grid;
  grid-template-columns: 1.5fr 1fr 1fr;
  gap: 40px;
  align-items: end;
  padding-top: 40px;
  border-top: 1px solid var(--rule);
}
.hero-tagline {
  font-family: var(--display-font);
  font-style: italic;
  font-size: clamp(18px, 2vw, 26px);
  line-height: 1.3;
  color: var(--ink-soft);
  max-width: 520px;
}
.hero-stat {
  font-family: var(--mono);
  font-size: 11px;
  text-transform: uppercase;
  letter-spacing: 0.12em;
  color: var(--ink-faint);
}
.hero-stat .num {
  display: block;
  font-family: var(--display-font);
  font-weight: 900;
  font-size: 56px;
  color: var(--ink);
  line-height: 1;
  margin-bottom: 8px;
  letter-spacing: -0.02em;
}

/* ====== NAVIGATION ====== */
.toc {
  padding: 80px 6vw;
  border-bottom: 2px solid var(--ink);
  background: var(--paper-dark);
}
.toc-label {
  font-family: var(--mono);
  font-size: 11px;
  text-transform: uppercase;
  letter-spacing: 0.15em;
  color: var(--ink-faint);
  margin-bottom: 24px;
}
.toc-heading {
  font-family: var(--display-font);
  font-size: clamp(36px, 5vw, 64px);
  font-weight: 700;
  line-height: 1;
  margin-bottom: 48px;
  letter-spacing: -0.02em;
}
.toc-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 0;
  border-top: 1px solid var(--ink);
}
.toc-item {
  padding: 24px 0;
  border-bottom: 1px solid var(--rule);
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  text-decoration: none;
  color: var(--ink);
  transition: padding 0.3s ease;
  position: relative;
}
.toc-item:nth-child(odd) { border-right: 1px solid var(--rule); padding-right: 32px; }
.toc-item:nth-child(even) { padding-left: 32px; }
.toc-item:hover { padding-left: 16px; background: var(--paper); }
.toc-item:nth-child(odd):hover { padding-left: 16px; padding-right: 32px; }
.toc-item:nth-child(even):hover { padding-left: 48px; }
.toc-item-num {
  font-family: var(--mono);
  font-size: 11px;
  color: var(--accent);
  letter-spacing: 0.1em;
}
.toc-item-name {
  font-family: var(--display-font);
  font-size: 22px;
  font-weight: 500;
  flex: 1;
  margin: 0 24px;
}
.toc-item-arrow {
  font-family: var(--mono);
  font-size: 14px;
  color: var(--ink-faint);
  transition: transform 0.3s ease, color 0.3s ease;
}
.toc-item:hover .toc-item-arrow {
  transform: translateX(8px);
  color: var(--accent);
}

/* ====== SECTIONS ====== */
section.chapter {
  padding: 100px 6vw 80px;
  border-bottom: 2px solid var(--ink);
  position: relative;
}
section.chapter:nth-child(even) { background: var(--paper-dark); }

.chapter-header {
  display: grid;
  grid-template-columns: auto 1fr;
  gap: 40px;
  align-items: end;
  margin-bottom: 64px;
  padding-bottom: 32px;
  border-bottom: 1px solid var(--rule);
}
.chapter-num {
  font-family: var(--display-font);
  font-weight: 900;
  font-style: italic;
  font-size: clamp(80px, 12vw, 180px);
  line-height: 0.8;
  color: var(--accent);
  letter-spacing: -0.04em;
}
.chapter-title-block { padding-bottom: 12px; }
.chapter-kicker {
  font-family: var(--mono);
  font-size: 11px;
  text-transform: uppercase;
  letter-spacing: 0.18em;
  color: var(--ink-faint);
  margin-bottom: 12px;
}
.chapter-title {
  font-family: var(--display-font);
  font-weight: 700;
  font-size: clamp(40px, 6vw, 80px);
  line-height: 0.95;
  letter-spacing: -0.025em;
}

.chapter-intro {
  max-width: 720px;
  font-size: 18px;
  line-height: 1.7;
  margin-bottom: 56px;
  color: var(--ink-soft);
}
.chapter-intro p + p { margin-top: 16px; }

/* ====== SKILL CARDS ====== */
.skill {
  display: grid;
  grid-template-columns: 1fr 1.1fr;
  gap: 0;
  margin-bottom: 56px;
  border: 1px solid var(--ink);
  background: var(--paper);
  position: relative;
}
.skill::before {
  content: "";
  position: absolute;
  top: -1px; left: -1px;
  width: 14px; height: 14px;
  background: var(--accent);
}
.skill-explainer {
  padding: 40px;
  border-right: 1px solid var(--rule);
  background: var(--paper);
}
.skill-tag {
  font-family: var(--mono);
  font-size: 10px;
  text-transform: uppercase;
  letter-spacing: 0.18em;
  color: var(--accent);
  margin-bottom: 14px;
}
.skill-name {
  font-family: var(--display-font);
  font-size: 32px;
  font-weight: 700;
  line-height: 1.05;
  letter-spacing: -0.02em;
  margin-bottom: 18px;
}
.skill-desc { font-size: 15px; line-height: 1.7; color: var(--ink-soft); margin-bottom: 18px; }
.skill-desc strong { color: var(--ink); font-weight: 600; }
.skill-desc + .skill-desc { margin-top: 16px; }
.skill-syntax {
  font-family: var(--mono);
  font-size: 13px;
  background: var(--code-bg);
  color: var(--code-fg);
  padding: 14px 16px;
  border-radius: 2px;
  margin: 18px 0;
  overflow-x: auto;
  white-space: pre;
}
.skill-syntax .arg { color: #ffd166; }
.skill-syntax .fn  { color: #06d6a0; }
.skill-syntax .com { color: #8a847a; font-style: italic; }
.skill-bullets { margin-top: 16px; padding-left: 0; list-style: none; }
.skill-bullets li {
  position: relative;
  padding-left: 22px;
  margin-bottom: 8px;
  font-size: 14px;
  color: var(--ink-soft);
  line-height: 1.6;
}
.skill-bullets li::before {
  content: "→";
  position: absolute;
  left: 0;
  color: var(--accent);
  font-family: var(--mono);
}

.skill-playground {
  padding: 40px;
  background: var(--paper-dark);
  display: flex;
  flex-direction: column;
}
.playground-label {
  font-family: var(--mono);
  font-size: 10px;
  text-transform: uppercase;
  letter-spacing: 0.18em;
  color: var(--ink-faint);
  margin-bottom: 14px;
  display: flex;
  align-items: center;
  gap: 8px;
}
.playground-label::before {
  content: "";
  width: 8px;
  height: 8px;
  background: var(--accent-2);
  border-radius: 50%;
}
.playground-instr {
  font-family: var(--display-font);
  font-style: italic;
  font-size: 18px;
  line-height: 1.4;
  margin-bottom: 20px;
  color: var(--ink);
}

/* ====== MINI SPREADSHEET ====== */
.sheet {
  display: grid;
  border: 1px solid var(--grid);
  background: #1a1612;
  overflow: hidden;
  font-family: var(--mono);
  font-size: 13px;
}
.sheet-row { display: contents; }
.sheet-cell {
  padding: 8px 10px;
  border-right: 1px solid var(--grid-soft);
  border-bottom: 1px solid var(--grid-soft);
  background: #1a1612;
  min-height: 32px;
  display: flex;
  align-items: center;
  position: relative;
  color: var(--ink);
}
.sheet-cell.head {
  background: #2d2620;
  color: var(--ink);
  font-weight: 600;
  text-align: center;
  justify-content: center;
  font-size: 11px;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}
.sheet-cell.row-head {
  background: #2d2620;
  font-weight: 600;
  justify-content: center;
  font-size: 11px;
}
.sheet-cell input {
  width: 100%;
  border: none;
  background: transparent;
  font-family: var(--mono);
  font-size: 13px;
  color: var(--ink);
  outline: none;
}
.sheet-cell input:focus { background: var(--highlight); }
.sheet-cell.formula-cell { background: var(--formula-bg); font-style: italic; color: var(--accent-2); }
.sheet-cell.result {
  background: #1f2e26;
  color: var(--accent-2);
  font-weight: 600;
}
.sheet-cell.input-cell { background: #261e15; }
.sheet-cell.given { background: #211c16; color: var(--ink-soft); }
.sheet-cell.right-edge { border-right: 1px solid var(--grid); }
.sheet-cell.bottom-edge { border-bottom: 1px solid var(--grid); }

/* ====== CONTROLS / BUTTONS ====== */
.btn-row { display: flex; gap: 10px; margin-top: 18px; flex-wrap: wrap; }
.btn {
  font-family: var(--mono);
  font-size: 11px;
  text-transform: uppercase;
  letter-spacing: 0.12em;
  padding: 10px 16px;
  border: 1px solid var(--ink);
  background: var(--paper);
  color: var(--ink);
  cursor: pointer;
  transition: all 0.2s ease;
  font-weight: 500;
}
.btn:hover { background: var(--ink); color: var(--paper); }
.btn.primary { background: var(--accent); border-color: var(--accent); color: #14110d; }
.btn.primary:hover { background: var(--ink); border-color: var(--ink); color: var(--paper); }
.btn.ghost { background: transparent; }

.feedback {
  margin-top: 14px;
  padding: 12px 14px;
  font-size: 13px;
  font-family: var(--mono);
  border-left: 3px solid transparent;
  background: transparent;
  min-height: 24px;
  transition: all 0.2s ease;
}
.feedback.ok { background: #1f2e26; border-color: var(--accent-2); color: var(--accent-2); }
.feedback.bad { background: #2e1a14; border-color: var(--accent); color: var(--accent); }
.feedback.hint { background: #2a2218; border-color: var(--accent-3); color: var(--accent-3); }

/* ====== EXAMPLE BLOCKS ====== */
.test-file {
  margin-bottom: 80px;
  border: 1px solid var(--rule);
  background: var(--paper-dark);
}
.test-file-header {
  padding: 28px 32px;
  border-bottom: 1px solid var(--rule);
  display: grid;
  grid-template-columns: auto 1fr auto;
  gap: 24px;
  align-items: center;
  background: #0a0807;
  color: var(--ink);
}
.test-file-icon {
  font-family: var(--display-font);
  font-style: italic;
  font-weight: 900;
  font-size: 40px;
  color: var(--accent-3);
  line-height: 1;
}
.test-file-title-block .filename {
  font-family: var(--mono);
  font-size: 11px;
  letter-spacing: 0.1em;
  color: var(--paper-dark);
  margin-bottom: 4px;
}
.test-file-title-block .title {
  font-family: var(--display-font);
  font-size: 26px;
  font-weight: 600;
  line-height: 1.1;
}
.test-file-stat {
  font-family: var(--mono);
  font-size: 10px;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  text-align: right;
  color: var(--paper-dark);
}
.test-file-stat strong { display: block; font-size: 22px; color: var(--paper); font-family: var(--display-font); }

.test-overview {
  padding: 28px 32px;
  border-bottom: 1px solid var(--rule);
  font-size: 15px;
  color: var(--ink-soft);
  line-height: 1.7;
}

.question {
  border-bottom: 1px solid var(--rule);
  padding: 32px;
}
.question:last-child { border-bottom: none; }
.question-tab {
  display: inline-block;
  font-family: var(--mono);
  font-size: 10px;
  letter-spacing: 0.15em;
  text-transform: uppercase;
  background: var(--accent);
  color: #14110d;
  padding: 4px 10px;
  margin-bottom: 12px;
}
.question-title {
  font-family: var(--display-font);
  font-size: 22px;
  font-weight: 600;
  margin-bottom: 8px;
  letter-spacing: -0.01em;
  line-height: 1.2;
}
.question-prompt {
  font-size: 14.5px;
  color: var(--ink-soft);
  margin-bottom: 16px;
  line-height: 1.65;
}
.question-prompt em { color: var(--ink); font-style: normal; font-weight: 600; }

.solution-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 0;
  border: 1px solid var(--rule);
  background: var(--paper-dark);
}
.solution-block { padding: 22px; }
.solution-block + .solution-block { border-left: 1px solid var(--rule); }
.solution-block h4 {
  font-family: var(--mono);
  font-size: 10px;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--accent-2);
  margin-bottom: 14px;
}
.solution-block .formula-display {
  font-family: var(--mono);
  background: var(--code-bg);
  color: var(--code-fg);
  padding: 12px 14px;
  font-size: 13px;
  border-radius: 2px;
  margin-bottom: 14px;
  overflow-x: auto;
  white-space: pre-wrap;
  word-break: break-word;
}
.solution-block ol { padding-left: 18px; }
.solution-block ol li {
  font-size: 13.5px;
  color: var(--ink-soft);
  margin-bottom: 8px;
  line-height: 1.55;
  padding-left: 4px;
}
.solution-block ol li::marker {
  font-family: var(--mono);
  font-weight: 700;
  color: var(--accent);
}
.solution-block p { font-size: 13.5px; color: var(--ink-soft); line-height: 1.6; margin-bottom: 8px; }
.solution-block p strong { color: var(--ink); }

/* ====== UTILITIES ====== */
.muted { color: var(--ink-faint); }
.kbd {
  font-family: var(--mono);
  font-size: 11px;
  background: var(--paper-dark);
  border: 1px solid var(--rule);
  padding: 2px 6px;
  border-radius: 3px;
  color: var(--ink);
  white-space: nowrap;
}
.tag {
  display: inline-block;
  font-family: var(--mono);
  font-size: 10px;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  padding: 3px 8px;
  background: var(--paper-dark);
  border: 1px solid var(--rule);
  margin-right: 6px;
  margin-bottom: 4px;
  color: var(--ink-soft);
}

/* Footer */
.footer {
  padding: 60px 6vw 40px;
  background: #0a0807;
  color: var(--ink);
  text-align: center;
  border-top: 2px solid var(--rule);
}
.footer .credit {
  font-family: var(--mono);
  font-size: 10px;
  text-transform: uppercase;
  letter-spacing: 0.2em;
  color: var(--ink-faint);
  margin-top: 16px;
}
.footer .seal {
  font-family: var(--display-font);
  font-style: italic;
  font-size: 28px;
  font-weight: 400;
  color: var(--accent-3);
}

/* ====== Responsive ====== */
@media (max-width: 900px) {
  .skill { grid-template-columns: 1fr; }
  .skill-explainer { border-right: none; border-bottom: 1px solid var(--rule); }
  .toc-grid { grid-template-columns: 1fr; }
  .toc-item:nth-child(odd) { border-right: none; padding-right: 0; }
  .toc-item:nth-child(even) { padding-left: 0; }
  .solution-grid { grid-template-columns: 1fr; }
  .solution-block + .solution-block { border-left: none; border-top: 1px solid var(--rule); }
  .chapter-header { grid-template-columns: 1fr; gap: 12px; }
  .hero-bot { grid-template-columns: 1fr; gap: 24px; }
  .test-file-header { grid-template-columns: 1fr; gap: 12px; text-align: left; }
  .test-file-stat { text-align: left; }
}

/* Form select dark styling */
select { color-scheme: dark; }
select option { background: var(--paper-dark); color: var(--ink); }

/* ====== EXAMPLE TWEAKS ====== */
.test-num {
  font-family: var(--display-font);
  font-style: italic;
  font-weight: 900;
  font-size: 44px;
  color: var(--accent-3);
  line-height: 1;
}
.test-file-header h3 {
  font-family: var(--display-font);
  font-size: 24px;
  font-weight: 600;
  letter-spacing: -0.01em;
  line-height: 1.15;
}
.test-file-header .filename {
  font-family: var(--mono);
  font-size: 11px;
  letter-spacing: 0.1em;
  color: var(--ink-faint);
  margin-bottom: 4px;
  text-transform: uppercase;
}
.test-file .overview {
  padding: 24px 32px;
  border-bottom: 1px solid var(--rule);
  font-size: 15px;
  color: var(--ink-soft);
  line-height: 1.7;
  font-style: italic;
}
.test-file .question {
  border-bottom: 1px solid var(--rule);
  padding: 28px 32px;
}
.test-file .question:last-child { border-bottom: none; }
.test-file .q-label {
  font-family: var(--mono);
  font-size: 11px;
  letter-spacing: 0.15em;
  text-transform: uppercase;
  color: var(--accent);
  margin-bottom: 10px;
  font-weight: 600;
}
.test-file .question > p {
  font-size: 14.5px;
  color: var(--ink-soft);
  margin-bottom: 16px;
  line-height: 1.65;
}
.formula-display {
  font-family: var(--mono);
  background: var(--code-bg);
  color: var(--accent-3);
  padding: 12px 14px;
  font-size: 13px;
  border: 1px solid var(--rule);
  margin: 10px 0;
  overflow-x: auto;
  white-space: pre-wrap;
  word-break: break-word;
  line-height: 1.5;
}

/* ====== GLOSSARY (Part 3) ====== */
.glossary {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
  gap: 0;
  border-top: 1px solid var(--rule);
  border-left: 1px solid var(--rule);
}
.gloss-card {
  padding: 24px 26px;
  border-right: 1px solid var(--rule);
  border-bottom: 1px solid var(--rule);
  background: var(--paper);
  transition: background 0.2s ease;
}
.gloss-card:hover { background: var(--paper-dark); }
.gloss-term {
  font-family: var(--display-font);
  font-weight: 700;
  font-size: 26px;
  color: var(--accent);
  letter-spacing: -0.01em;
  line-height: 1.1;
}
.gloss-expand {
  font-family: var(--mono);
  font-size: 11px;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--ink-faint);
  margin: 6px 0 14px;
}
.gloss-formula {
  font-family: var(--mono);
  font-size: 12px;
  background: var(--code-bg);
  color: var(--accent-3);
  padding: 8px 10px;
  border: 1px solid var(--rule);
  margin-bottom: 12px;
  overflow-x: auto;
  white-space: pre-wrap;
  word-break: break-word;
}
.gloss-desc {
  font-size: 13.5px;
  color: var(--ink-soft);
  line-height: 1.65;
}
.gloss-desc strong { color: var(--ink); font-weight: 600; }

/* ====== PLAYBOOK (Part 4) ====== */
.playbook {
  border-top: 1px solid var(--rule);
}
.play {
  padding: 36px 0;
  border-bottom: 1px solid var(--rule);
}
.play:last-child { border-bottom: none; }
.play-header {
  display: grid;
  grid-template-columns: auto 1fr;
  gap: 24px;
  align-items: baseline;
  margin-bottom: 18px;
}
.play-num {
  font-family: var(--display-font);
  font-style: italic;
  font-weight: 900;
  font-size: 56px;
  color: var(--accent-2);
  line-height: 1;
  width: 60px;
}
.play-title {
  font-family: var(--display-font);
  font-size: 28px;
  font-weight: 600;
  letter-spacing: -0.015em;
  line-height: 1.15;
}
.play-prompt {
  margin-left: 84px;
  font-size: 15px;
  color: var(--ink-soft);
  line-height: 1.7;
  font-style: italic;
  margin-bottom: 18px;
  max-width: 760px;
}
.play .solution-block,
.play .solution-grid {
  margin-left: 84px;
}
@media (max-width: 700px) {
  .play-prompt, .play .solution-block, .play .solution-grid { margin-left: 0; }
  .play-num { font-size: 44px; }
}

/* ====== CHALLENGES (Part 5) ====== */
.challenges {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(380px, 1fr));
  gap: 0;
  border-top: 1px solid var(--rule);
  border-left: 1px solid var(--rule);
}
.challenge {
  padding: 28px 26px 24px;
  border-right: 1px solid var(--rule);
  border-bottom: 1px solid var(--rule);
  background: var(--paper);
  display: flex;
  flex-direction: column;
}
.ch-num {
  font-family: var(--mono);
  font-size: 10px;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--accent-3);
  font-weight: 600;
  margin-bottom: 8px;
}
.ch-title {
  font-family: var(--display-font);
  font-size: 22px;
  font-weight: 600;
  letter-spacing: -0.01em;
  line-height: 1.2;
  margin-bottom: 12px;
}
.ch-prompt {
  font-size: 14px;
  color: var(--ink-soft);
  line-height: 1.65;
  margin-bottom: 18px;
}
.ch-prompt em { color: var(--ink); font-style: normal; font-weight: 600; }
.ch-input-row {
  display: flex;
  align-items: stretch;
  border: 1px solid var(--rule);
  background: var(--code-bg);
  margin-bottom: 0;
}
.ch-prefix {
  font-family: var(--mono);
  font-size: 14px;
  font-weight: 700;
  color: var(--accent);
  padding: 12px 14px;
  border-right: 1px solid var(--rule);
  background: #050403;
  display: flex;
  align-items: center;
}
.ch-input {
  flex: 1;
  background: transparent;
  border: none;
  outline: none;
  font-family: var(--mono);
  font-size: 13px;
  color: var(--ink);
  padding: 12px 14px;
}
.ch-input::placeholder { color: var(--ink-faint); font-style: italic; }
.ch-input:focus { background: rgba(224,123,90,0.08); }
.challenge .btn-row { margin-top: 14px; }
.challenge .feedback { margin-top: 12px; font-size: 12px; word-break: break-all; }
@media (max-width: 700px) {
  .glossary, .challenges { grid-template-columns: 1fr; }
}

/* ====== TAB BAR ====== */
.tab-bar {
  position: sticky;
  top: 0;
  z-index: 100;
  background: var(--paper-dark);
  border-bottom: 2px solid var(--ink);
  box-shadow: 0 4px 24px rgba(0,0,0,0.5);
}
.tab-bar-inner {
  display: flex;
  align-items: center;
  gap: 0;
  padding: 0 6vw;
}
.tab-bar-label {
  font-family: var(--mono);
  font-size: 10px;
  text-transform: uppercase;
  letter-spacing: 0.18em;
  color: var(--ink-faint);
  margin-right: 20px;
  white-space: nowrap;
}
.tab-btn {
  font-family: var(--mono);
  font-size: 11px;
  text-transform: uppercase;
  letter-spacing: 0.12em;
  padding: 18px 28px;
  border: none;
  border-bottom: 3px solid transparent;
  background: transparent;
  color: var(--ink-soft);
  cursor: pointer;
  transition: all 0.2s ease;
  display: flex;
  align-items: center;
  gap: 8px;
  margin-bottom: -2px;
  font-weight: 500;
}
.tab-btn:hover { color: var(--ink); background: rgba(240,233,216,0.04); }
.tab-btn.active { color: var(--ink); border-bottom-color: var(--accent); }
.tab-icon { font-size: 14px; }
.wfm-only { display: none; }
body.wfm-active .wfm-only { display: block; }
.wfm-only { animation: fadeIn 0.3s ease; }
@keyframes fadeIn { from { opacity: 0; transform: translateY(8px); } to { opacity: 1; transform: translateY(0); } }
/* TOC items for WFM hidden by default */
.toc-item.wfm-only { display: none; }
body.wfm-active .toc-item.wfm-only { display: flex; }