:root {
  --bg: #081426;
  --bg-soft: #0d1d33;
  --surface: #12243d;
  --surface-2: #172d49;
  --paper: #f4f7fb;
  --paper-soft: #e8eef6;
  --ink: #edf4ff;
  --ink-muted: #aebbd0;
  --navy-text: #0a1930;
  --accent: #ffb000;
  --accent-2: #49c6e5;
  --accent-3: #ff6b57;
  --green: #66d19e;
  --border: rgba(255, 255, 255, 0.13);
  --shadow: 0 24px 70px rgba(0, 0, 0, 0.26);
  --radius: 18px;
  --max: 1220px;
}

* { box-sizing: border-box; }

html {
  scroll-behavior: smooth;
  scroll-padding-top: 84px;
}

body {
  margin: 0;
  color: var(--ink);
  background: var(--bg);
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  font-size: 16px;
  line-height: 1.65;
  transition: background-color 180ms ease, color 180ms ease;
}

body.light {
  --bg: #eaf0f8;
  --bg-soft: #dfe8f4;
  --surface: #ffffff;
  --surface-2: #f3f7fc;
  --ink: #10213a;
  --ink-muted: #53647b;
  --border: rgba(10, 25, 48, 0.15);
  --shadow: 0 22px 60px rgba(21, 42, 72, 0.13);
}

a { color: inherit; }
button, summary { font: inherit; }
button { color: inherit; }

.skip-link {
  position: fixed;
  z-index: 100;
  left: 1rem;
  top: -4rem;
  padding: .75rem 1rem;
  background: var(--accent);
  color: #101820;
  font-weight: 800;
  border-radius: 8px;
}

.skip-link:focus { top: 1rem; }

.site-header {
  position: sticky;
  z-index: 50;
  top: 0;
  display: grid;
  grid-template-columns: auto 1fr auto;
  align-items: center;
  gap: 2rem;
  min-height: 72px;
  padding: .75rem max(1.25rem, calc((100vw - var(--max)) / 2));
  border-bottom: 1px solid var(--border);
  background: color-mix(in srgb, var(--bg) 88%, transparent);
  backdrop-filter: blur(18px);
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: .7rem;
  text-decoration: none;
  font-size: .82rem;
  letter-spacing: .08em;
  white-space: nowrap;
}

.brand strong { color: var(--accent); }

.brand-mark {
  display: grid;
  place-items: center;
  width: 34px;
  height: 34px;
  background: var(--accent);
  color: #111827;
  border-radius: 9px 9px 9px 2px;
  font-size: 1.1rem;
  font-weight: 950;
}

.top-nav {
  display: flex;
  justify-content: center;
  gap: 1.6rem;
}

.top-nav a {
  color: var(--ink-muted);
  text-decoration: none;
  font-size: .82rem;
  font-weight: 700;
  letter-spacing: .04em;
}

.top-nav a:hover, .top-nav a.active { color: var(--accent); }

.header-actions { display: flex; gap: .55rem; }

.icon-button, .print-button {
  min-height: 40px;
  border: 1px solid var(--border);
  background: var(--surface);
  border-radius: 10px;
  cursor: pointer;
}

.icon-button { width: 40px; font-size: 1.2rem; }
.print-button { padding: 0 1rem; font-weight: 750; }
.icon-button:hover, .print-button:hover { border-color: var(--accent); }

.cover {
  position: relative;
  isolation: isolate;
  display: grid;
  grid-template-columns: minmax(0, 1.25fr) minmax(340px, .75fr);
  gap: clamp(2rem, 6vw, 6rem);
  align-items: center;
  min-height: calc(100vh - 72px);
  padding: clamp(4rem, 8vw, 8rem) max(1.25rem, calc((100vw - var(--max)) / 2));
  overflow: hidden;
}

.cover::before {
  content: "";
  position: absolute;
  z-index: -2;
  inset: 8% auto auto 48%;
  width: 42vw;
  height: 42vw;
  border: 1px solid color-mix(in srgb, var(--accent-2) 25%, transparent);
  border-radius: 50%;
  box-shadow: 0 0 90px color-mix(in srgb, var(--accent-2) 10%, transparent), inset 0 0 90px color-mix(in srgb, var(--accent) 6%, transparent);
}

.cover-grid {
  position: absolute;
  z-index: -3;
  inset: 0;
  opacity: .24;
  background-image: linear-gradient(var(--border) 1px, transparent 1px), linear-gradient(90deg, var(--border) 1px, transparent 1px);
  background-size: 50px 50px;
  mask-image: linear-gradient(to right, black, transparent 86%);
}

.eyebrow, .section-kicker {
  margin: 0 0 1rem;
  color: var(--accent);
  font-size: .77rem;
  font-weight: 850;
  letter-spacing: .14em;
  text-transform: uppercase;
}

.eyebrow span {
  display: inline-block;
  margin-right: .3rem;
  padding: .25rem .55rem;
  color: #111827;
  background: var(--accent);
  border-radius: 3px;
}

h1, h2, h3, p { overflow-wrap: anywhere; }

h1 {
  margin: 0;
  max-width: 790px;
  font-size: clamp(3.7rem, 8vw, 7.8rem);
  line-height: .89;
  letter-spacing: -.065em;
  font-weight: 900;
}

h1 em { color: var(--accent); font-style: normal; }

.cover-lead {
  max-width: 680px;
  margin: 2.2rem 0;
  color: var(--ink-muted);
  font-size: clamp(1.05rem, 2vw, 1.3rem);
  line-height: 1.6;
}

.audience-note {
  display: grid;
  grid-template-columns: auto 1fr;
  gap: 1rem;
  max-width: 650px;
  padding: 1rem 0;
  border-top: 1px solid var(--border);
  border-bottom: 1px solid var(--border);
}

.audience-note p { margin: 0; color: var(--ink-muted); }
.note-index { color: var(--accent-2); font-size: .7rem; font-weight: 900; letter-spacing: .15em; }

.cover-actions { display: flex; align-items: center; gap: 1.5rem; margin-top: 2.2rem; }

.primary-button {
  display: inline-flex;
  align-items: center;
  gap: 1rem;
  min-height: 52px;
  padding: 0 1.25rem;
  color: #111827;
  background: var(--accent);
  border-radius: 10px;
  text-decoration: none;
  font-weight: 850;
  box-shadow: 5px 5px 0 color-mix(in srgb, var(--accent-3) 80%, #000 20%);
}

.text-link { color: var(--ink-muted); text-underline-offset: 4px; }

.cover-panel {
  border: 1px solid var(--border);
  background: color-mix(in srgb, var(--surface) 92%, transparent);
  border-radius: 26px 26px 26px 6px;
  box-shadow: var(--shadow);
  overflow: hidden;
}

.qr-card {
  display: grid;
  grid-template-columns: 100px 1fr;
  gap: 1.2rem;
  align-items: center;
  padding: 1.25rem;
  border-bottom: 1px solid var(--border);
  background: var(--paper);
  color: var(--navy-text);
}

.qr-visual {
  display: grid;
  place-items: center;
  width: 100px;
  height: 100px;
  overflow: hidden;
  border-radius: 8px;
  background: #fff;
}

.qr-visual img { display: block; width: 100%; height: 100%; }

.qr-placeholder {
  position: relative;
  display: grid;
  grid-template-columns: 1fr 1fr;
  width: 84px;
  height: 84px;
  padding: 6px;
  gap: 22px;
  background-image: repeating-linear-gradient(45deg, #dfe6ef 0 3px, transparent 3px 7px);
}

.qr-placeholder span { width: 24px; height: 24px; border: 6px solid #0b1a2e; background: white; }
.qr-placeholder span:nth-child(3) { grid-column: 1; }
.qr-placeholder b { position: absolute; inset: 34px 23px auto auto; padding: 2px 5px; color: #0b1a2e; background: #ffb000; font-size: .6rem; }
.qr-label { margin: 0; font-size: .76rem; font-weight: 900; letter-spacing: .12em; text-transform: uppercase; }
.qr-card p:last-child { margin: .25rem 0 0; color: #4e5c70; font-size: .82rem; line-height: 1.35; }

.route-list { margin: 0; padding: 0; list-style: none; }
.route-list li { display: grid; grid-template-columns: auto 1fr; gap: 1rem; padding: 1.25rem 1.5rem; border-bottom: 1px solid var(--border); }
.route-number { color: var(--accent); font-family: ui-monospace, SFMono-Regular, Consolas, monospace; font-weight: 800; }
.route-list strong { display: block; }
.route-list small { display: block; margin-top: .15rem; color: var(--ink-muted); line-height: 1.45; }
.outcome { padding: 1.25rem 1.5rem; background: color-mix(in srgb, var(--accent-2) 8%, transparent); }
.outcome span { color: var(--accent-2); font-size: .7rem; font-weight: 900; letter-spacing: .12em; text-transform: uppercase; }
.outcome p { margin: .35rem 0 0; color: var(--ink-muted); font-size: .9rem; }

.how-to, .part, .transition {
  width: min(var(--max), calc(100% - 2.5rem));
  margin-inline: auto;
}

.how-to { padding: 6rem 0; }

h2 {
  margin: 0;
  font-size: clamp(2.25rem, 5vw, 4.6rem);
  line-height: 1.02;
  letter-spacing: -.045em;
}

.how-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 1px; margin-top: 3rem; background: var(--border); border: 1px solid var(--border); border-radius: var(--radius); overflow: hidden; }
.how-grid article { position: relative; padding: 2rem; background: var(--surface); }
.how-grid article > span { color: var(--accent); font-family: ui-monospace, SFMono-Regular, Consolas, monospace; font-size: .8rem; font-weight: 800; }
.how-grid h3 { margin: 2rem 0 .5rem; font-size: 1.15rem; }
.how-grid p { margin: 0; color: var(--ink-muted); }

.tool-row { display: grid; grid-template-columns: repeat(3, 1fr); gap: 1px; margin-top: 1rem; overflow: hidden; border: 1px solid var(--border); border-radius: 12px; background: var(--border); }
.tool-row div { display: flex; align-items: center; justify-content: space-between; gap: 1rem; padding: .9rem 1rem; background: var(--bg-soft); }
.tool-row span { color: var(--ink-muted); font-size: .72rem; font-weight: 800; text-transform: uppercase; }
.tool-row code { color: var(--accent-2); }

.part { padding: 7rem 0 3rem; }
.part-header { display: grid; grid-template-columns: 120px 1fr 260px; gap: 2rem; align-items: start; margin-bottom: 4rem; }
.part-header > div:nth-child(2) > p:last-child { max-width: 700px; color: var(--ink-muted); font-size: 1.12rem; }
.part-id { display: flex; flex-direction: column; align-items: flex-start; }
.part-id span { padding: .2rem .5rem; color: #111827; background: var(--accent); font-size: .65rem; font-weight: 950; letter-spacing: .13em; }
.part-id strong { font-size: 5rem; line-height: 1; letter-spacing: -.08em; }
.part-goal { padding: 1.2rem; border-top: 3px solid var(--accent); background: var(--surface); }
.part-goal span { color: var(--accent); font-size: .7rem; font-weight: 900; letter-spacing: .12em; text-transform: uppercase; }
.part-goal p { margin: .35rem 0 0; color: var(--ink-muted); font-size: .9rem; }

.syntax-grid { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 1rem; margin: 2rem 0; }
.syntax-card { padding: clamp(1.25rem, 3vw, 2rem); border: 1px solid var(--border); background: var(--surface); border-radius: var(--radius); }
.syntax-card--wide { grid-column: 1 / -1; }
.syntax-card h3 { margin: .25rem 0 .75rem; font-size: 1.35rem; }
.syntax-card > p { color: var(--ink-muted); }
.card-label { color: var(--accent-2); font-size: .7rem; font-weight: 900; letter-spacing: .14em; text-transform: uppercase; }
.mini-code { display: grid; gap: .45rem; margin: 1rem 0; }
.mini-code code, .menu-preview code { display: block; padding: .55rem .75rem; color: #b9e8ff; background: #07111f; border-left: 2px solid var(--accent-2); border-radius: 3px; }
.tip, .warning, .hint { padding: .8rem 1rem; border-left: 3px solid var(--accent-2); background: color-mix(in srgb, var(--accent-2) 7%, transparent); font-size: .9rem; }
.warning { border-color: var(--accent-3); background: color-mix(in srgb, var(--accent-3) 8%, transparent); }

code, pre { font-family: "Cascadia Code", "SFMono-Regular", Consolas, monospace; }
:not(pre) > code { padding: .08rem .28rem; border-radius: 4px; color: color-mix(in srgb, var(--accent-2) 78%, var(--ink)); background: color-mix(in srgb, var(--accent-2) 8%, transparent); font-size: .9em; }

.code-shell { min-width: 0; margin-top: 1.15rem; border: 1px solid #263957; background: #07111f; border-radius: 12px; overflow: hidden; }
.code-shell.compact pre { max-height: 330px; }
.code-toolbar { display: flex; justify-content: space-between; align-items: center; min-height: 44px; padding: .5rem .65rem .5rem 1rem; border-bottom: 1px solid #263957; color: #8799b4; background: #0c192b; font-size: .75rem; }
.copy-button { padding: .4rem .75rem; border: 1px solid #354a69; color: #d9e7fa; background: #13233a; border-radius: 7px; cursor: pointer; font-size: .75rem; font-weight: 800; }
.copy-button:hover, .copy-button:focus-visible { border-color: var(--accent); color: var(--accent); }
pre { margin: 0; padding: 1.2rem; overflow: auto; color: #d8e6f8; font-size: .86rem; line-height: 1.62; tab-size: 4; }
pre code { color: inherit; }

.comparison-strip { margin: 2rem 0 4rem; border: 1px solid var(--border); border-radius: 14px; overflow-x: auto; }
.comparison-strip > div { display: grid; grid-template-columns: 1fr 1.1fr 1.45fr 1.45fr; min-width: 760px; border-bottom: 1px solid var(--border); }
.comparison-strip > div:last-child { border-bottom: 0; }
.comparison-strip span, .comparison-strip b, .comparison-strip code { padding: .8rem 1rem; border-right: 1px solid var(--border); }
.comparison-strip > div:first-child { background: var(--surface-2); }
.comparison-strip b { color: var(--accent); font-size: .8rem; text-transform: uppercase; }
.comparison-strip span { color: var(--ink-muted); font-size: .8rem; font-weight: 800; }

.exercise-list { display: grid; gap: 1.25rem; }
.exercise { display: grid; grid-template-columns: 130px 1fr; border: 1px solid var(--border); background: var(--surface); border-radius: var(--radius); overflow: hidden; }
.exercise-meta { padding: 1.5rem 1.25rem; border-right: 1px solid var(--border); background: var(--surface-2); }
.exercise-number { display: block; color: var(--accent); font-family: ui-monospace, SFMono-Regular, Consolas, monospace; font-size: .82rem; font-weight: 900; }
.difficulty { display: block; margin-top: 1rem; color: var(--ink-muted); font-size: .7rem; line-height: 1.3; }
.exercise-body { padding: 1.5rem 2rem; }
.exercise-body h3 { margin: 0 0 .6rem; font-size: 1.45rem; }
.exercise-body p { margin: 0; color: var(--ink-muted); }
.exercise-body p + p { margin-top: 1rem; }
.expected { display: grid; gap: .5rem; margin-top: 1rem; padding: .9rem; border: 1px dashed var(--border); border-radius: 8px; }
.expected span { color: var(--accent-2); font-size: .68rem; font-weight: 900; letter-spacing: .1em; text-transform: uppercase; }
.checks { display: flex; flex-wrap: wrap; gap: .5rem; margin: 1rem 0 0; padding: 0; list-style: none; }
.checks li { padding: .35rem .65rem; border: 1px solid var(--border); border-radius: 999px; color: var(--ink-muted); font-size: .8rem; }

.solution { grid-column: 1 / -1; border-top: 1px solid var(--border); }
.solution summary { display: flex; justify-content: space-between; align-items: center; gap: 1rem; padding: 1rem 1.5rem; color: var(--accent); cursor: pointer; font-weight: 850; list-style: none; }
.solution summary::-webkit-details-marker { display: none; }
.solution summary::after { content: "+"; display: grid; place-items: center; width: 28px; height: 28px; border: 1px solid var(--border); border-radius: 50%; font-size: 1.1rem; }
.solution[open] summary::after { content: "−"; }
.solution summary small { margin-left: auto; color: var(--ink-muted); font-weight: 500; }
.solution-content { padding: 0 1.5rem 1.5rem; border-top: 1px solid var(--border); }
.solution-content .code-shell { margin-top: 1.5rem; }
.explanation { margin: 1rem 0 0; color: var(--ink-muted); font-size: .92rem; }

.checkpoint { display: grid; grid-template-columns: auto 1fr auto; gap: 1.5rem; align-items: center; margin-top: 2rem; padding: 1.25rem 1.5rem; border: 1px solid color-mix(in srgb, var(--green) 45%, transparent); background: color-mix(in srgb, var(--green) 7%, transparent); border-radius: 14px; }
.checkpoint > div { display: flex; align-items: center; gap: .65rem; }
.checkpoint > div span { display: grid; place-items: center; width: 28px; height: 28px; color: #092418; background: var(--green); border-radius: 50%; font-weight: 950; }
.checkpoint p { margin: 0; color: var(--ink-muted); }
.complete-button { padding: .6rem .9rem; border: 1px solid var(--green); color: var(--green); background: transparent; border-radius: 8px; cursor: pointer; font-weight: 800; }
.complete-button.is-complete { color: #092418; background: var(--green); }

.parallel-visual { margin-bottom: 2rem; padding: 1.5rem; border: 1px solid var(--border); background: #07111f; border-radius: var(--radius); overflow-x: auto; }
.parallel-label { display: flex; justify-content: space-between; gap: 1rem; min-width: 680px; margin-bottom: 1rem; }
.parallel-label span { color: var(--accent-2); font-size: .7rem; font-weight: 900; letter-spacing: .12em; text-transform: uppercase; }
.parallel-label strong { color: #aebbd0; font-size: .85rem; }
.array-row { display: grid; grid-template-columns: 110px repeat(3, 1fr); min-width: 680px; }
.array-row b, .array-row code { padding: .75rem 1rem; border-top: 1px solid #263957; border-right: 1px solid #263957; }
.array-row b { color: var(--accent); }
.array-row code { color: #d8e6f8; }
.array-row code.active { color: #07111f; background: var(--accent-2); }

.concept-flow { display: grid; grid-template-columns: .65fr auto 1.35fr; gap: 1.5rem; align-items: center; margin-bottom: 2rem; padding: 1.5rem; border: 1px solid var(--border); background: var(--surface); border-radius: var(--radius); }
.flow-main { padding: 1.2rem; border: 2px solid var(--accent); text-align: center; }
.flow-main span { display: block; color: var(--accent); font-family: ui-monospace, SFMono-Regular, Consolas, monospace; font-weight: 900; }
.flow-main small { color: var(--ink-muted); }
.concept-flow > span { color: var(--accent); font-size: 2rem; }
.flow-methods { display: grid; grid-template-columns: repeat(2, 1fr); gap: .5rem; }
.flow-methods code { padding: .65rem; text-align: center; border: 1px solid var(--border); background: var(--bg-soft); }

.exercise--final { border-color: color-mix(in srgb, var(--accent) 55%, transparent); }
.menu-preview { display: grid; grid-template-columns: repeat(3, 1fr); gap: .35rem; margin-top: 1rem; }
.test-cases { margin-top: 1.5rem; padding: 1rem 1.25rem; border: 1px solid var(--border); border-radius: 10px; }
.test-cases h4 { margin: 0; color: var(--accent); }
.test-cases ol { margin-bottom: 0; color: var(--ink-muted); }

.transition { display: grid; grid-template-columns: 140px 1fr 1fr; gap: 2.5rem; align-items: center; margin-top: 7rem; margin-bottom: 7rem; padding: clamp(1.5rem, 5vw, 3.5rem); color: #0b192d; background: var(--accent); border-radius: 26px 26px 26px 6px; box-shadow: 10px 10px 0 var(--accent-3); }
.transition .section-kicker { color: #5b4000; }
.transition h2 { font-size: clamp(2rem, 4vw, 3.5rem); }
.transition p { color: #4e3d18; }
.transition-number { display: flex; flex-direction: column; font-size: 5rem; font-weight: 950; line-height: .9; }
.transition-number span { font-size: 2rem; }
.before-after { display: grid; grid-template-columns: 1fr auto 1fr; gap: .8rem; align-items: center; }
.before-after > div { display: grid; gap: .35rem; }
.before-after span { font-size: .7rem; font-weight: 900; text-transform: uppercase; }
.before-after code { padding: .4rem; color: #d8e6f8; background: #07111f; border-radius: 3px; font-size: .75rem; }

footer { display: flex; justify-content: space-between; align-items: center; gap: 2rem; padding: 2rem max(1.25rem, calc((100vw - var(--max)) / 2)); border-top: 1px solid var(--border); color: var(--ink-muted); font-size: .85rem; }
footer a:last-child { color: var(--accent); }

.toast { position: fixed; z-index: 100; right: 1.25rem; bottom: 1.25rem; max-width: min(360px, calc(100vw - 2.5rem)); padding: .8rem 1rem; color: #07111f; background: var(--green); border-radius: 10px; box-shadow: var(--shadow); font-weight: 800; transform: translateY(140%); transition: transform 180ms ease; }
.toast.show { transform: translateY(0); }

@media (max-width: 960px) {
  .site-header { grid-template-columns: 1fr auto; }
  .top-nav { display: none; }
  .cover { grid-template-columns: 1fr; min-height: auto; }
  .cover-panel { max-width: 680px; }
  .part-header { grid-template-columns: 90px 1fr; }
  .part-goal { grid-column: 2; }
  .checkpoint { grid-template-columns: 1fr; }
  .transition { grid-template-columns: 90px 1fr; }
  .before-after { grid-column: 1 / -1; }
}

@media (max-width: 700px) {
  html { scroll-padding-top: 68px; }
  .site-header { min-height: 64px; gap: .75rem; }
  .brand { font-size: .72rem; }
  .brand-mark { width: 30px; height: 30px; }
  .print-button { display: none; }
  .cover { padding-top: 3.5rem; }
  h1 { font-size: clamp(3.25rem, 17vw, 5.2rem); }
  .cover-actions { align-items: flex-start; flex-direction: column; }
  .qr-card { grid-template-columns: 82px 1fr; }
  .qr-visual { width: 82px; height: 82px; }
  .qr-placeholder { transform: scale(.8); }
  .how-grid, .tool-row, .syntax-grid { grid-template-columns: 1fr; }
  .syntax-card--wide { grid-column: auto; }
  .tool-row div { align-items: flex-start; flex-direction: column; gap: .3rem; }
  .part { padding-top: 5rem; }
  .part-header { grid-template-columns: 1fr; gap: 1rem; }
  .part-id { flex-direction: row; align-items: end; gap: .4rem; }
  .part-id strong { font-size: 3.5rem; }
  .part-goal { grid-column: auto; }
  .exercise { grid-template-columns: 1fr; }
  .exercise-meta { display: flex; justify-content: space-between; align-items: center; padding: .8rem 1rem; border-right: 0; border-bottom: 1px solid var(--border); }
  .difficulty { margin: 0; }
  .exercise-body { padding: 1.25rem; }
  .solution summary { align-items: flex-start; padding: 1rem; }
  .solution summary small { display: none; }
  .solution-content { padding: 0 1rem 1rem; }
  pre { font-size: .78rem; }
  .concept-flow { grid-template-columns: 1fr; }
  .concept-flow > span { transform: rotate(90deg); text-align: center; }
  .flow-methods { grid-template-columns: 1fr; }
  .menu-preview { grid-template-columns: 1fr 1fr; }
  .transition { grid-template-columns: 1fr; }
  .transition-number { flex-direction: row; align-items: center; gap: .5rem; }
  .before-after { grid-column: auto; grid-template-columns: 1fr; }
  .before-after > span { transform: rotate(90deg); text-align: center; }
  footer { align-items: flex-start; flex-direction: column; }
}

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { scroll-behavior: auto !important; transition: none !important; }
}

@media print {
  :root { --ink: #111827; --ink-muted: #40506a; --surface: #fff; --surface-2: #f3f6fa; --border: #cbd5e1; }
  body { color: #111827; background: #fff; font-size: 10pt; }
  .site-header, .copy-button, .complete-button, .toast, footer { display: none !important; }
  .cover { min-height: 100vh; grid-template-columns: 1.2fr .8fr; padding: 2cm 1.5cm; break-after: page; }
  .cover-grid { opacity: .08; }
  .cover::before { display: none; }
  h1 { font-size: 55pt; }
  .cover-lead, .audience-note p, .route-list small, .outcome p { color: #40506a; }
  .cover-panel { border: 1px solid #aab5c4; box-shadow: none; }
  .how-to, .part, .transition { width: auto; margin-inline: 1.5cm; }
  .how-to { padding: 1cm 0; }
  .part { padding-top: 1.2cm; }
  .exercise, .syntax-card, .checkpoint { break-inside: avoid; }
  .solution:not([open]) { display: none; }
  .solution[open] summary { display: none; }
  .code-shell { border-color: #bdc7d4; background: #f5f7fa; }
  .code-toolbar { color: #40506a; background: #e8edf3; border-color: #bdc7d4; }
  pre { color: #111827; white-space: pre-wrap; }
  .transition { margin-block: 1.5cm; box-shadow: none; }
}