:root {
  --ink: #121924;
  --ink-soft: #4c586a;
  --slate: #161d28;
  --slate-deep: #0e141d;
  --slate-line: #2b3644;
  --paper: #f1f4f8;
  --paper-deep: #e4e9f0;
  --white: #ffffff;
  --line: #ccd4e0;
  --ember: #ff6b2c;
  --ember-soft: #ff8b57;
  --azure: #5aa9ff;
  --amber: #f2a63b;
  --violet: #9d8cff;
  --teal: #3ecfbb;
  --mono: ui-monospace, "SFMono-Regular", Consolas, "Liberation Mono", monospace;
  --sans: Inter, ui-sans-serif, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  --serif: Iowan Old Style, "Palatino Linotype", Palatino, Georgia, serif;
  --step--1: clamp(.78rem, .75rem + .12vw, .86rem);
  --step-0: clamp(.98rem, .93rem + .2vw, 1.1rem);
  --step-1: clamp(1.15rem, 1.02rem + .55vw, 1.45rem);
  --step-2: clamp(1.5rem, 1.2rem + 1.25vw, 2.25rem);
  --step-3: clamp(2.2rem, 1.6rem + 2.5vw, 4rem);
  --step-4: clamp(3.5rem, 2.1rem + 5.8vw, 7.5rem);
  --space-1: .5rem;
  --space-2: .85rem;
  --space-3: 1.25rem;
  --space-4: 2rem;
  --space-5: 3.5rem;
  --space-6: clamp(5rem, 9vw, 9rem);
  --radius-sm: .4rem;
  --radius: 1rem;
  --radius-lg: 1.75rem;
  --shadow: 0 18px 55px rgba(18, 25, 36, .14);
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  color: var(--ink);
  background: var(--paper);
  font-family: var(--sans);
  font-size: var(--step-0);
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
}
body::selection { color: var(--white); background: var(--ember); }
a { color: inherit; text-decoration-thickness: .08em; text-underline-offset: .2em; }
a:hover { text-decoration-color: var(--ember); }
img, svg { max-width: 100%; }
button, input { font: inherit; }
button { color: inherit; }
code, pre { font-family: var(--mono); }
code {
  padding: .12em .35em;
  border-radius: .25em;
  color: #294059;
  background: rgba(22, 29, 40, .08);
  font-size: .9em;
}
/* Inline code also appears inside the dark sections, where the default ink is unreadable. */
.hero code, .path code, .challenge code, .setup-trouble code, .finish-line code, footer code {
  color: #ffb287;
  background: rgba(255, 255, 255, .1);
}
kbd {
  padding: .15em .45em;
  border: 1px solid var(--line);
  border-bottom-width: 3px;
  border-radius: .3rem;
  background: var(--white);
  font: .85em var(--mono);
}
dfn { font-style: normal; font-weight: 750; }
:focus-visible { outline: 3px solid var(--ember); outline-offset: 4px; }
[id] { scroll-margin-top: 7rem; }
/* Alias targets so links written as #tutorial-N or #start-here also land correctly. */
.anchor-alias { display: block; height: 0; overflow: hidden; }
.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}
.skip-link {
  position: fixed;
  z-index: 100;
  top: .75rem;
  left: .75rem;
  padding: .7rem 1rem;
  color: var(--white);
  background: var(--slate);
  transform: translateY(-200%);
}
.skip-link:focus { transform: none; }

.site-header {
  position: sticky;
  z-index: 50;
  top: 0;
  display: grid;
  grid-template-columns: 1fr auto 1fr;
  align-items: center;
  min-height: 74px;
  padding: .6rem clamp(1rem, 3vw, 3rem);
  color: var(--white);
  border-bottom: 1px solid rgba(255,255,255,.12);
  background: rgba(22, 29, 40, .94);
  backdrop-filter: blur(12px);
}
.brand {
  display: inline-flex;
  align-items: center;
  gap: .7rem;
  width: max-content;
  color: inherit;
  font-weight: 780;
  line-height: 1.05;
  text-decoration: none;
  letter-spacing: -.02em;
}
.brand small {
  display: block;
  margin-top: .15rem;
  color: #9aa7b8;
  font: 600 .62rem/1.2 var(--mono);
  letter-spacing: .09em;
  text-transform: uppercase;
}
.brand-mark {
  display: grid;
  width: 2.35rem;
  height: 2.35rem;
  place-items: center;
  color: var(--white);
  border-radius: 50% 50% 44% 56%;
  background: var(--ember);
  font: italic 800 1.4rem var(--serif);
  transform: rotate(-6deg);
}
.site-nav { display: flex; gap: clamp(1rem, 2.4vw, 2.4rem); }
.site-nav a {
  color: #cdd6e2;
  font-size: .79rem;
  font-weight: 700;
  text-decoration: none;
  text-transform: uppercase;
  letter-spacing: .09em;
}
.site-nav a:hover { color: var(--ember); }
.header-progress {
  display: flex;
  align-items: center;
  justify-self: end;
  gap: .75rem;
  font: 650 .72rem var(--mono);
  color: #b3bfcd;
}
.header-progress strong { color: var(--ember); }
.progress-track { width: 72px; height: 4px; overflow: hidden; background: #384454; }
.progress-track span { display: block; width: 0; height: 100%; background: var(--ember); transition: width .35s ease; }
.nav-toggle { display: none; border: 0; background: transparent; }

.hero {
  position: relative;
  display: grid;
  grid-template-columns: minmax(0, 1.05fr) minmax(340px, .75fr);
  gap: clamp(2rem, 7vw, 8rem);
  min-height: calc(100vh - 74px);
  padding: clamp(5rem, 10vw, 9rem) clamp(1.25rem, 7vw, 8rem);
  overflow: hidden;
  color: var(--white);
  background: var(--slate);
}
.hero-grid {
  position: absolute;
  inset: 0;
  opacity: .22;
  background-image: linear-gradient(rgba(255,255,255,.08) 1px, transparent 1px), linear-gradient(90deg, rgba(255,255,255,.08) 1px, transparent 1px);
  background-size: 52px 52px;
  mask-image: linear-gradient(to right, #000, transparent 82%);
}
.hero-orbit {
  position: absolute;
  border: 1px solid rgba(255, 107, 44, .3);
  border-radius: 50%;
  pointer-events: none;
}
.orbit-one { width: 42vw; height: 42vw; right: -13vw; top: -18vw; }
.orbit-two { width: 26vw; height: 26vw; right: -4vw; top: -11vw; }
.hero-copy, .hero-art { position: relative; z-index: 1; }
.eyebrow, .kicker, .content-label {
  font: 750 var(--step--1)/1.2 var(--mono);
  text-transform: uppercase;
  letter-spacing: .12em;
}
.eyebrow { display: flex; align-items: center; gap: .8rem; color: #a9b6c6; }
.eyebrow span { width: 2rem; height: 1px; background: var(--ember); }
.hero h1 {
  max-width: 850px;
  margin: .5rem 0 1.5rem;
  font: 700 var(--step-4)/.88 var(--serif);
  letter-spacing: -.065em;
}
.hero h1 em { color: var(--ember); font-weight: 400; }
.hero-deck { max-width: 690px; color: #bfcad8; font-size: var(--step-1); line-height: 1.5; }
.hero-actions { display: flex; flex-wrap: wrap; gap: .8rem; margin-top: 2.2rem; }
.button {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 1rem;
  min-height: 52px;
  padding: .7rem 1.25rem;
  border: 1px solid rgba(255,255,255,.3);
  font-weight: 760;
  font-size: .9rem;
  text-decoration: none;
}
.button-primary { color: var(--white); border-color: var(--ember); background: var(--ember); }
.button-primary:hover { background: var(--ember-soft); }
.button-ghost:hover { border-color: var(--white); }
.hero-facts {
  display: flex;
  gap: 0;
  margin: clamp(3rem, 8vh, 6rem) 0 0;
  padding: 0;
  list-style: none;
}
.hero-facts li {
  display: flex;
  flex-direction: column;
  min-width: 130px;
  padding: 0 1.5rem;
  border-left: 1px solid #384454;
}
.hero-facts li:first-child { padding-left: 0; border-left: 0; }
.hero-facts strong { color: var(--ember); font: 500 var(--step-2)/1 var(--serif); }
.hero-facts span { margin-top: .4rem; color: #8f9cad; font-size: .72rem; }
.hero-art { align-self: center; }
.terminal-window {
  overflow: hidden;
  border: 1px solid rgba(255,255,255,.16);
  border-radius: var(--radius);
  box-shadow: 0 35px 80px rgba(0,0,0,.32);
  background: var(--slate-deep);
  transform: rotate(1.5deg);
}
.terminal-bar {
  display: flex;
  align-items: center;
  gap: .4rem;
  height: 44px;
  padding: 0 1rem;
  border-bottom: 1px solid #232e3b;
  background: #151d27;
}
.terminal-bar span { width: 8px; height: 8px; border-radius: 50%; background: #4a5768; }
.terminal-bar small { margin-left: auto; color: #7d8a9b; font: .62rem var(--mono); }
.terminal-body { min-height: 310px; padding: 2rem; color: #d3dbe6; font: clamp(.72rem, 1.2vw, .9rem)/1.8 var(--mono); }
.terminal-body p { margin: .25rem 0; }
.terminal-body .prompt, .terminal-success { color: var(--ember); }
.terminal-muted { color: #7b8798; }
.terminal-rule { height: 1px; margin: 1.25rem 0; background: #263140; }
.terminal-output { display: flex; justify-content: space-between; color: #b6c2d1; }
.terminal-output b { color: var(--azure); }
.terminal-cursor { color: var(--ember); animation: blink 1.1s steps(2, start) infinite; }
.scribble-note {
  width: max-content;
  margin: 2.5rem 0 0 auto;
  color: var(--ember);
  font: italic 1.05rem/1.35 var(--serif);
  transform: rotate(-4deg);
}
.scribble-note span { display: inline-block; font: 1.5rem var(--sans); transform: rotate(20deg); }
@keyframes blink { 50% { opacity: 0; } }

.section-shell, .toc-shell { padding: var(--space-6) clamp(1.25rem, 7vw, 8rem); }
.section-label {
  display: flex;
  align-items: center;
  gap: .8rem;
  margin-bottom: var(--space-5);
  color: #6b788a;
  font: 700 .7rem var(--mono);
  text-transform: uppercase;
  letter-spacing: .13em;
}
.section-label::after { content: ""; flex: 1; height: 1px; background: var(--line); }
.section-label span { color: var(--ember); }
.toc-shell { background: var(--white); }
.toc-intro {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 4rem;
  align-items: end;
  margin-bottom: var(--space-5);
}
.toc-intro h2, .section-heading h2 {
  margin: 0;
  font: 500 var(--step-3)/1.02 var(--serif);
  letter-spacing: -.045em;
}
.toc-intro p, .section-heading > p:last-child { max-width: 580px; margin: 0; color: var(--ink-soft); }
.toc { border-top: 1px solid var(--ink); }
.toc a {
  display: grid;
  grid-template-columns: 70px 1fr auto;
  gap: 1rem;
  align-items: center;
  min-height: 88px;
  padding: .9rem .25rem;
  border-bottom: 1px solid var(--line);
  text-decoration: none;
  transition: padding .2s ease, background .2s ease;
}
.toc a:hover { padding-right: 1rem; padding-left: 1rem; background: var(--paper); }
.toc-num { color: var(--ember); font: 650 .8rem var(--mono); }
.toc strong { display: block; font: 550 var(--step-1) var(--serif); }
.toc small { display: block; color: #6d7a8c; font: .7rem var(--mono); }
.toc a > span:last-child { color: var(--ember); font-size: 1.4rem; }

.setup { background: var(--paper); }
.section-heading { display: grid; grid-template-columns: minmax(250px, .8fr) 1.2fr; gap: 0 4rem; margin-bottom: var(--space-5); }
.section-heading .kicker { grid-column: 1 / -1; color: var(--ember); }
/* Titles the two halves of setup so the word tiles never read as the numbered steps. */
.block-intro { margin-bottom: 1.5rem; }
.block-intro h3 { margin: 0 0 .3rem; font: 550 var(--step-1) var(--serif); letter-spacing: -.02em; }
.block-intro p { max-width: 620px; margin: 0; color: var(--ink-soft); font-size: .85rem; }
.definition-strip + .block-intro { padding-top: var(--space-4); border-top: 1px solid var(--line); }
.definition-strip {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  margin-bottom: var(--space-5);
  border-top: 1px solid var(--ink);
  border-left: 1px solid var(--line);
}
.definition-strip article { min-height: 175px; padding: 1.25rem; border-right: 1px solid var(--line); border-bottom: 1px solid var(--line); }
.definition-strip span { color: var(--ember); font: 700 .65rem var(--mono); }
.definition-strip h3 { margin: .6rem 0 .25rem; font: 600 1.25rem var(--serif); }
.definition-strip p { margin: 0; color: var(--ink-soft); font-size: .82rem; line-height: 1.5; }
.journey { max-width: 1020px; margin: 0 auto; padding: 0; list-style: none; }
.journey-step { display: grid; grid-template-columns: 60px minmax(0, 1fr); gap: 1.2rem; }
.journey-marker { position: relative; display: flex; justify-content: center; }
.journey-marker::after { content: ""; position: absolute; z-index: 0; top: 46px; bottom: -1px; width: 1px; background: var(--line); }
.journey-step:last-child .journey-marker::after { display: none; }
.journey-marker span {
  position: relative;
  z-index: 1;
  display: grid;
  width: 44px;
  height: 44px;
  place-items: center;
  color: var(--white);
  border: 5px solid var(--paper);
  border-radius: 50%;
  background: var(--slate);
  font: 700 .78rem var(--mono);
}
.journey-card {
  margin-bottom: 1.4rem;
  padding: clamp(1.4rem, 3vw, 2.7rem);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--white);
  box-shadow: 0 5px 0 rgba(18,25,36,.03);
}
.step-topline { display: flex; flex-wrap: wrap; justify-content: space-between; align-items: center; gap: .5rem 1rem; }
.step-label, .step-state { margin: 0; color: var(--ember); font: 700 .65rem var(--mono); text-transform: uppercase; letter-spacing: .1em; }
.step-state { padding: .35rem .55rem; color: #566375; border-radius: 3rem; background: var(--paper-deep); }
.journey-card h3 { margin: .5rem 0; font: 550 var(--step-2) var(--serif); letter-spacing: -.02em; }
.journey-card h4 { margin: 0; font-size: .9rem; }
.journey-card > p { color: var(--ink-soft); }
.os-grid, .split-code { display: grid; grid-template-columns: 1fr 1fr; gap: 1rem; }
.os-card { padding: 1.25rem; border: 1px solid var(--line); background: #f7f9fc; }
.os-card h4 span { color: var(--ember); }
.os-card ol { margin-bottom: 0; padding-left: 1.2rem; font-size: .83rem; }
.os-card li + li { margin-top: .55rem; }
.command-intro { margin-top: 1.5rem; font-weight: 650; }
.code-block { overflow: hidden; margin: 1rem 0; border-radius: var(--radius-sm); background: var(--slate); }
.code-head { display: flex; justify-content: space-between; align-items: center; min-height: 38px; padding: .4rem .8rem; color: #93a1b3; border-bottom: 1px solid #2e3948; background: #1b2331; font: .62rem var(--mono); text-transform: uppercase; letter-spacing: .08em; }
.code-head button { padding: .25rem .5rem; color: #c2ccd9; border: 1px solid #45525f; border-radius: .2rem; background: transparent; cursor: pointer; }
.code-head button:hover { color: var(--white); border-color: var(--ember); background: var(--ember); }
.os-toggle { display: inline-flex; gap: .2rem; margin-left: auto; margin-right: .65rem; padding: .16rem; border: 1px solid #45525f; border-radius: 999px; }
.os-toggle button { min-width: 4.4rem; border: 0; border-radius: 999px; }
.os-toggle button.is-active { color: var(--white); background: var(--ember); }
.code-block pre[hidden] { display: none; }
.code-block pre { margin: 0; padding: 1rem; overflow-x: auto; color: #e8edf4; font: .8rem/1.7 var(--mono); }
.code-block code { padding: 0; color: inherit; background: none; font-size: inherit; }
.expected { position: relative; margin: 1rem 0; padding: 1.5rem 1.2rem 1rem; border: 1px solid #b8c6d8; border-radius: var(--radius-sm); background: #eef3f9; }
.expected > span { position: absolute; top: -.65rem; left: 1rem; padding: .1rem .5rem; color: #2a4763; background: #d5e2f0; font: 750 .61rem var(--mono); text-transform: uppercase; letter-spacing: .08em; }
.expected pre { margin: 0; overflow-x: auto; color: #2b455f; font: .76rem/1.6 var(--mono); white-space: pre-wrap; }
.expected p { margin: .4rem 0 0; color: #5d6b7d; font-size: .72rem; }
.checkpoint, .callout { display: flex; gap: 1rem; align-items: flex-start; margin-top: 1.25rem; padding: 1rem; border-left: 3px solid var(--azure); background: #eaf2fd; }
.checkpoint > span, .callout-icon { display: grid; flex: 0 0 1.6rem; height: 1.6rem; place-items: center; border-radius: 50%; color: var(--white); background: #2f6fc4; font: 750 .75rem var(--mono); }
.checkpoint strong, .callout strong { font-size: .8rem; }
.checkpoint p, .callout p { margin: 0; font-size: .79rem; }
.callout-warn { border-color: var(--amber); background: #fff3e2; }
.callout-warn .callout-icon { color: var(--slate); background: var(--amber); }
.callout-practice { border-color: var(--violet); background: #efedfd; }
.callout-practice .callout-icon { background: #6f5edb; }
.setup-trouble { max-width: 940px; margin: 2rem auto 0; padding: 1.5rem 2rem; color: var(--white); border-radius: var(--radius); background: var(--slate); }
.setup-trouble > div { display: flex; align-items: center; gap: 1rem; }
.setup-trouble > div span { display: grid; width: 2rem; height: 2rem; place-items: center; color: var(--white); border-radius: 50%; background: var(--ember); font-weight: 800; }
.setup-trouble h3 { margin: 0; font: 500 1.35rem var(--serif); }
.setup-trouble details { margin-left: 3rem; border-top: 1px solid #384454; }
.setup-trouble summary { padding: .8rem 0; color: #d5dde8; cursor: pointer; font-size: .83rem; font-weight: 700; }
.setup-trouble details p { color: #a7b3c2; font-size: .78rem; }

.path { color: var(--white); background: var(--slate); }
.path .section-label { color: #8b9aad; }
.path .section-label::after { background: #33404f; }
.path .section-heading > p:last-child { color: #a9b6c6; }
.module-grid { display: grid; grid-template-columns: repeat(6, 1fr); gap: 1rem; }
.module-card {
  position: relative;
  display: flex;
  grid-column: span 2;
  flex-direction: column;
  min-height: 390px;
  padding: 1.5rem;
  overflow: hidden;
  color: var(--slate);
  text-decoration: none;
  transition: transform .25s ease, box-shadow .25s ease;
}
.module-card:nth-child(4) { grid-column: 2 / span 2; }
.module-card:hover { transform: translateY(-7px) rotate(-.4deg); box-shadow: 0 20px 0 rgba(0,0,0,.2); }
.module-card::after { content: ""; position: absolute; right: -50px; bottom: -60px; width: 180px; height: 180px; border: 1px solid rgba(18,25,36,.2); border-radius: 50%; }
.module-card-1 { background: var(--ember); }
.module-card-2 { background: var(--azure); }
.module-card-3 { background: var(--amber); }
.module-card-4 { background: var(--teal); }
.module-card-5 { background: var(--violet); }
.module-index { font: 700 .65rem var(--mono); letter-spacing: .08em; }
.module-icon { position: absolute; top: 1rem; right: 1.2rem; font: 2.2rem var(--serif); }
.module-card h3 { margin: 3rem 0 .7rem; font: 600 2.3rem/.92 var(--serif); letter-spacing: -.05em; }
.module-card p { margin: 0; font-size: .84rem; line-height: 1.5; }
.module-card ul { display: flex; flex-wrap: wrap; gap: .35rem; margin: 1.2rem 0; padding: 0; list-style: none; }
.module-card li { padding: .25rem .5rem; border: 1px solid rgba(18,25,36,.35); border-radius: 3rem; font: 650 .6rem var(--mono); text-transform: uppercase; }
.module-cta { z-index: 1; margin-top: auto; font-size: .73rem; font-weight: 760; }

.lessons { background: var(--white); }
.lesson { border-bottom: 12px solid var(--paper); }
.lesson-hero {
  display: grid;
  grid-template-columns: 150px minmax(300px, 1.2fr) minmax(260px, .7fr);
  gap: clamp(1.5rem, 4vw, 5rem);
  align-items: end;
  padding: var(--space-6) clamp(1.25rem, 7vw, 8rem) var(--space-5);
  border-bottom: 1px solid var(--line);
}
.lesson-number { display: flex; flex-direction: column; color: var(--ember); }
.lesson-number span, .lesson-number small { font: 700 .66rem var(--mono); text-transform: uppercase; letter-spacing: .1em; }
.lesson-number strong { margin: .2rem 0; font: 500 6.5rem/.78 var(--serif); letter-spacing: -.08em; }
.lesson-title .kicker { color: var(--ember); }
.lesson-title h2 { margin: .7rem 0 1rem; font: 600 var(--step-3)/.95 var(--serif); letter-spacing: -.055em; }
.lesson-title h2 em { color: var(--ember); font-weight: 400; }
.lesson-title > p:last-child { max-width: 700px; color: var(--ink-soft); font-size: var(--step-1); }
.lesson-meta { padding-left: 1.5rem; border-left: 1px solid var(--line); }
.lesson-meta p { margin: 1rem 0; color: var(--ink-soft); font-size: .8rem; }
.lesson-meta span { display: block; margin-bottom: .2rem; color: var(--ink); font: 750 .62rem var(--mono); text-transform: uppercase; }
.lesson-body {
  display: grid;
  grid-template-columns: minmax(180px, .26fr) minmax(0, 1fr);
  gap: clamp(2rem, 6vw, 7rem);
  padding: var(--space-5) clamp(1.25rem, 7vw, 8rem) var(--space-6);
}
.lesson-rail { align-self: start; position: sticky; top: 105px; padding: 1.25rem; border-top: 3px solid var(--ember); background: var(--paper); }
.lesson-rail p { margin: 0; color: #677486; font: 700 .62rem var(--mono); text-transform: uppercase; }
.lesson-rail > strong { display: block; margin: .5rem 0; font: 500 2.6rem var(--serif); }
.lesson-rail > strong span { color: #8b96a5; font-size: 1rem; }
.mini-progress { display: flex; gap: 4px; margin-bottom: 1rem; }
.mini-progress span { flex: 1; height: 4px; background: #c7cfdb; }
.mini-progress .active { background: var(--ember); }
.lesson-rail a { display: block; padding: .65rem 0; border-top: 1px solid var(--line); font-size: .7rem; font-weight: 700; text-decoration: none; }
.lesson-content { max-width: 900px; }
.lesson-content > section { margin-bottom: clamp(3.5rem, 7vw, 6rem); }
.content-label { margin: 0 0 .7rem; color: var(--ember); font-size: .66rem; }
.lesson-content h3 { margin: 0 0 1rem; font: 550 var(--step-2) var(--serif); letter-spacing: -.03em; }
.concept > p:not(.content-label) { max-width: 760px; color: var(--ink-soft); }
.flow-diagram { display: flex; align-items: center; justify-content: space-between; gap: .7rem; margin: 2rem 0; padding: 1.2rem; border: 1px dashed #9aa5b4; background: var(--paper); }
.flow-diagram span { padding: .5rem .7rem; text-align: center; background: var(--white); font: 650 .68rem var(--mono); }
.flow-diagram b { color: var(--ember); }
.concept-list { margin: 2rem 0 0; padding: 0; border-top: 1px solid var(--ink); list-style: none; }
.concept-list li { display: grid; grid-template-columns: 180px 1fr; gap: 1rem; padding: .9rem 0; border-bottom: 1px solid var(--line); }
.concept-list strong { font-family: var(--serif); }
.concept-list span { color: var(--ink-soft); font-size: .82rem; }
.lesson-steps { margin: 2rem 0 0; padding: 0; list-style: none; }
.lesson-steps > li { display: grid; grid-template-columns: 42px 1fr; gap: 1rem; padding: 1.8rem 0; border-top: 1px solid var(--line); }
.lesson-steps > li:last-child { border-bottom: 1px solid var(--line); }
.step-num { display: grid; width: 36px; height: 36px; place-items: center; color: var(--white); border-radius: 50%; background: var(--slate); font: 750 .7rem var(--mono); }
.lesson-steps h4 { margin: .15rem 0 .5rem; font: 600 1.2rem var(--serif); }
.lesson-steps p { margin: .6rem 0; color: var(--ink-soft); font-size: .88rem; }
.lesson-steps .code-block { max-width: 720px; }
.lesson-steps .inspect { padding-left: .8rem; border-left: 2px solid var(--azure); font-size: .78rem; }
.expected.compact { max-width: 720px; }
.challenge { display: grid; grid-template-columns: auto 1fr; gap: 1.5rem; padding: clamp(1.5rem, 4vw, 3rem); color: var(--white); background: var(--slate); }
.challenge-mark { display: grid; width: 3rem; height: 3rem; place-items: center; color: var(--white); border-radius: 50%; background: var(--ember); font-size: 1.7rem; }
.challenge .content-label { color: var(--ember); }
.challenge h3 { margin-bottom: .4rem; }
.challenge p:last-child { margin: 0; color: #bfcad8; }
.finish { display: grid; grid-template-columns: 1fr .8fr; gap: 2rem; align-items: start; }
.finish ul { margin: 1.5rem 0 0; padding: 0; list-style: none; }
.finish li { padding: .55rem 0; border-bottom: 1px solid var(--line); font-size: .84rem; }
.finish li span { margin-right: .6rem; color: #c25317; font-weight: 800; }
.troubleshoot { padding: 1.2rem; border: 1px solid var(--line); background: var(--paper); }
.troubleshoot summary { cursor: pointer; font: 650 .85rem var(--serif); }
.troubleshoot p { color: var(--ink-soft); font-size: .75rem; }
.complete-control {
  display: flex;
  gap: 1rem;
  align-items: center;
  padding: 1.3rem;
  border: 2px solid var(--slate);
  cursor: pointer;
}
.complete-control input { position: absolute; width: 1px; height: 1px; opacity: 0; }
.custom-check { display: grid; flex: 0 0 2rem; height: 2rem; place-items: center; border: 2px solid var(--slate); }
.complete-control input:checked + .custom-check { background: var(--slate); }
.complete-control input:checked + .custom-check::after { content: "✓"; color: var(--ember); font-weight: 800; }
.complete-control input:focus-visible + .custom-check { outline: 3px solid var(--ember); outline-offset: 3px; }
.complete-control strong, .complete-control small { display: block; }
.complete-control small { color: var(--ink-soft); font-size: .68rem; }
.lesson.is-complete .lesson-number { color: #9c5a33; }
.lesson-nav { display: grid; grid-template-columns: 1fr 1fr; border-top: 1px solid var(--line); }
.lesson-nav a { padding: 2rem clamp(1.25rem, 7vw, 8rem); text-decoration: none; font: 550 var(--step-1) var(--serif); }
.lesson-nav a + a { text-align: right; border-left: 1px solid var(--line); }
.lesson-nav a:hover { background: var(--paper); }
.lesson-nav span { display: block; margin-bottom: .3rem; color: var(--ember); font: 700 .6rem var(--mono); text-transform: uppercase; letter-spacing: .08em; }

.finish-line {
  display: grid;
  grid-template-columns: auto minmax(0, 1fr) minmax(0, 1fr);
  gap: clamp(2rem, 5vw, 5rem);
  align-items: center;
  color: var(--white);
  background: var(--slate);
}
.finish-line h2 { margin: .5rem 0 1rem; font: 500 var(--step-3)/1 var(--serif); letter-spacing: -.05em; }
.finish-line > div > p:last-child { color: #b3bfcd; }
.finish-line .kicker { color: var(--ember); }
.finish-stamp {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  width: 145px;
  height: 145px;
  color: var(--ember);
  border: 2px solid var(--ember);
  border-radius: 50%;
  transform: rotate(-7deg);
}
.finish-stamp::before { content: "✦"; }
.finish-stamp span, .finish-stamp small { font: 650 .55rem var(--mono); text-transform: uppercase; letter-spacing: .12em; }
.finish-stamp strong { font: 500 2.5rem var(--serif); }
.finish-line aside { padding: 1.5rem; color: var(--ink); border-top: 3px solid var(--ember); background: var(--paper); }
.finish-line aside h3 { margin-top: 0; font: 600 1.3rem var(--serif); }
.finish-line aside > p { font-size: .78rem; }
.finish-line aside p code { color: #294059; background: rgba(22, 29, 40, .08); }
.light-code { background: var(--slate-deep); }
.fine-print { color: var(--ink-soft); }
.glossary { background: var(--paper-deep); }
.glossary dl { display: grid; grid-template-columns: repeat(3, 1fr); margin: 3rem 0 0; border-top: 1px solid var(--ink); border-left: 1px solid var(--line); }
.glossary dl div { min-height: 150px; padding: 1.25rem; border-right: 1px solid var(--line); border-bottom: 1px solid var(--line); }
.glossary dt { margin-bottom: .5rem; font: 600 1.15rem var(--serif); }
.glossary dd { margin: 0; color: var(--ink-soft); font-size: .78rem; line-height: 1.55; }
footer {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 2rem;
  padding: 2rem clamp(1.25rem, 7vw, 8rem);
  color: var(--white);
  border-top: 1px solid #33404f;
  background: var(--slate);
}
footer p { color: #97a4b4; font-size: .7rem; }
footer > a:last-child { font-size: .72rem; font-weight: 700; }

@media (max-width: 980px) {
  .site-header { grid-template-columns: 1fr auto; }
  .header-progress { display: none; }
  .hero { grid-template-columns: 1fr; min-height: auto; }
  .hero-art { max-width: 600px; }
  .module-grid { grid-template-columns: 1fr 1fr; }
  .module-card, .module-card:nth-child(4) { grid-column: auto; }
  .module-card:last-child { grid-column: 1 / -1; min-height: 300px; }
  .lesson-hero { grid-template-columns: 100px 1fr; }
  .lesson-number strong { font-size: 4.8rem; }
  .lesson-meta { grid-column: 2; display: flex; gap: 2rem; padding-left: 0; border: 0; }
  .lesson-body { grid-template-columns: 150px minmax(0, 1fr); gap: 2rem; }
  .finish-line { grid-template-columns: auto minmax(0, 1fr); }
  .finish-line aside { grid-column: 1 / -1; }
  .glossary dl { grid-template-columns: repeat(2, 1fr); }
}

@media (max-width: 720px) {
  [id] { scroll-margin-top: 4.8rem; }
  .site-header { min-height: 64px; }
  .nav-toggle { display: grid; width: 44px; height: 44px; place-content: center; gap: 7px; cursor: pointer; }
  .nav-toggle span:not(.sr-only) { display: block; width: 22px; height: 2px; background: var(--white); transition: transform .2s ease; }
  .nav-toggle[aria-expanded="true"] span:nth-of-type(2) { transform: translateY(4.5px) rotate(45deg); }
  .nav-toggle[aria-expanded="true"] span:nth-of-type(3) { transform: translateY(-4.5px) rotate(-45deg); }
  .site-nav {
    position: absolute;
    top: 100%;
    right: 0;
    left: 0;
    display: none;
    flex-direction: column;
    gap: 0;
    padding: .5rem 1.25rem 1rem;
    border-top: 1px solid #384454;
    background: var(--slate);
  }
  .site-nav.is-open { display: flex; }
  .site-nav a { padding: .85rem 0; border-bottom: 1px solid #384454; }
  .hero { padding-top: 4rem; }
  .hero h1 { font-size: clamp(3.2rem, 15vw, 5rem); }
  .hero-facts { flex-wrap: wrap; row-gap: 1.5rem; }
  .hero-facts li { min-width: 105px; padding: 0 1rem; }
  .terminal-body { min-height: 260px; padding: 1.2rem; }
  .toc-intro, .section-heading { grid-template-columns: 1fr; gap: 1rem; }
  .toc a { grid-template-columns: 45px 1fr auto; }
  .toc small { margin-top: .3rem; }
  .definition-strip { grid-template-columns: 1fr 1fr; }
  .journey-step { grid-template-columns: 38px minmax(0, 1fr); gap: .5rem; }
  .journey-marker span { width: 34px; height: 34px; border-width: 3px; }
  .journey-marker::after { top: 34px; }
  .journey-card { padding: 1.2rem; }
  .code-head { flex-wrap: wrap; gap: .45rem; }
  .code-head > span { flex-basis: 100%; }
  .os-toggle { margin-left: 0; margin-right: auto; }
  .os-grid, .split-code { grid-template-columns: 1fr; }
  .setup-trouble { padding: 1.2rem; }
  .setup-trouble details { margin-left: 0; }
  .module-grid { grid-template-columns: 1fr; }
  .module-card, .module-card:nth-child(4), .module-card:last-child { grid-column: auto; min-height: 330px; }
  .lesson-hero { grid-template-columns: 70px 1fr; gap: 1rem; }
  .lesson-number strong { font-size: 3.5rem; }
  .lesson-title > p:last-child { font-size: 1rem; }
  .lesson-meta { grid-column: 1 / -1; }
  .lesson-body { display: block; }
  .lesson-rail { position: static; margin-bottom: 3rem; }
  .flow-diagram { flex-wrap: wrap; justify-content: center; }
  .agent-flow b { transform: rotate(90deg); }
  .concept-list li { grid-template-columns: 1fr; gap: .25rem; }
  .finish { grid-template-columns: 1fr; }
  .lesson-nav a { padding: 1.5rem 1rem; font-size: .95rem; }
  .finish-line { grid-template-columns: minmax(0, 1fr); }
  .finish-stamp { width: 110px; height: 110px; }
  .finish-line aside { grid-column: auto; }
  .glossary dl { grid-template-columns: 1fr; }
  footer { flex-direction: column; align-items: flex-start; }
}

@media (max-width: 440px) {
  .hero-actions .button { width: 100%; }
  .hero-facts li { flex: 1; }
  .definition-strip { grid-template-columns: 1fr; }
  .toc a { grid-template-columns: 35px 1fr; }
  .toc a > span:last-child { display: none; }
  .lesson-hero { display: block; }
  .lesson-number { flex-direction: row; align-items: baseline; gap: .5rem; margin-bottom: 1.5rem; }
  .lesson-number strong { font-size: 2.5rem; }
  .lesson-meta { display: block; }
  .lesson-steps > li { grid-template-columns: 1fr; }
  .challenge { grid-template-columns: 1fr; }
  .lesson-nav { grid-template-columns: 1fr; }
  .lesson-nav a + a { border-top: 1px solid var(--line); border-left: 0; }
}

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

@media print {
  .site-header, .hero-art, .hero-orbit, .hero-grid, .complete-control, .lesson-nav, footer { display: none; }
  .hero { min-height: 0; color: var(--ink); background: var(--white); }
  .hero h1 em { color: var(--ink); }
  .hero-deck { color: var(--ink-soft); }
  .lesson-rail { position: static; }
  .code-block { break-inside: avoid; }
  .lesson { break-before: page; }
}