/* ==========================================================================
   Coding with Dom — design system
   One stylesheet, driven by custom properties. Dark mode redefines a handful
   of tokens and every component follows automatically.
   ========================================================================== */

/* ------------------------------------------------------------------ tokens */

:root {
  /* Light blue brand ramp */
  --brand-50:  #f0f7ff;
  --brand-100: #dceeff;
  --brand-200: #b8dcff;
  --brand-300: #85c4ff;
  --brand-400: #4aa5ff;
  --brand-500: #1b84f3;
  --brand-600: #0a68d4;
  --brand-700: #0a52a8;
  --brand-800: #0d4485;
  --brand-900: #0f3a6e;

  --cyan: #22d3ee;
  --violet: #7c5cff;

  /* Brand blue as *type*. The ramp above is tuned for fills and gradients;
     these two are the variants that clear 4.5:1 against light surfaces, and
     they flip to the light end of the ramp in dark mode. */
  --brand-text: #0a5fc0;
  --brand-text-strong: #0d4485;

  /* Surfaces */
  --page:        #f4f9ff;
  --page-alt:    #eaf3ff;
  --surface:     #ffffff;
  --surface-2:   #f7fbff;
  --surface-3:   #eef6ff;
  --line:        #d7e7fa;
  --line-strong: #bcd8f5;

  /* Ink */
  --ink:        #0c1c30;
  --ink-2:      #26395a;
  --ink-muted:  #546a92;
  --ink-faint:  #5b6f91;
  --on-brand:   #ffffff;

  /* Code surface — dark in both themes, it is a terminal */
  --code-bg:    #0c1728;
  --code-bg-2:  #101f36;
  --code-line:  #1d3151;
  --code-ink:   #d5e5fb;

  /* Spacing scale */
  --s-1: 0.25rem;
  --s-2: 0.5rem;
  --s-3: 0.75rem;
  --s-4: 1rem;
  --s-5: 1.25rem;
  --s-6: 1.5rem;
  --s-8: 2rem;
  --s-10: 2.5rem;
  --s-12: 3rem;
  --s-16: 4rem;
  --s-20: 5rem;
  --s-24: 6rem;

  /* Type scale */
  --t-xs:  0.78rem;
  --t-sm:  0.875rem;
  --t-base: 1rem;
  --t-md:  1.0625rem;
  --t-lg:  1.1875rem;
  --t-xl:  1.5rem;
  --t-2xl: 1.9rem;
  --t-3xl: 2.4rem;
  --t-4xl: clamp(2.4rem, 5.6vw, 4rem);

  --font: ui-sans-serif, system-ui, -apple-system, "Segoe UI", Roboto,
          "Helvetica Neue", Arial, sans-serif;
  --mono: ui-monospace, "SF Mono", "JetBrains Mono", "Fira Code", Menlo,
          Consolas, "Liberation Mono", monospace;

  --radius-sm: 8px;
  --radius: 14px;
  --radius-lg: 20px;
  --radius-xl: 28px;

  --shadow-sm: 0 1px 2px rgb(12 28 48 / 0.05), 0 1px 3px rgb(12 28 48 / 0.04);
  --shadow: 0 1px 2px rgb(12 28 48 / 0.05), 0 10px 24px -12px rgb(12 28 48 / 0.18);
  --shadow-lg: 0 2px 4px rgb(12 28 48 / 0.05), 0 24px 56px -20px rgb(10 82 168 / 0.28);
  --shadow-brand: 0 1px 2px rgb(10 82 168 / 0.3), 0 12px 28px -12px rgb(10 82 168 / 0.55);

  --shell: 78rem;
  --header-h: 68px;

  --ease: cubic-bezier(0.22, 0.61, 0.36, 1);
}

:root[data-theme='dark'] {
  --page:        #070e1b;
  --page-alt:    #0a1526;
  --surface:     #0f1c30;
  --surface-2:   #132339;
  --surface-3:   #172b45;
  --line:        #1f3454;
  --line-strong: #2b4468;

  --ink:       #e9f2ff;
  --ink-2:     #c2d6f0;
  --ink-muted: #8fa8ca;
  --ink-faint: #7b94b5;

  --brand-50:  #10233c;
  --brand-100: #16304f;
  --brand-200: #1d4374;

  --brand-text: #7cc4ff;
  --brand-text-strong: #a5d8ff;

  --code-bg:   #08111f;
  --code-bg-2: #0c1a2d;
  --code-line: #1a2c49;

  --shadow-sm: 0 1px 2px rgb(0 0 0 / 0.4);
  --shadow: 0 1px 2px rgb(0 0 0 / 0.4), 0 12px 28px -14px rgb(0 0 0 / 0.7);
  --shadow-lg: 0 2px 6px rgb(0 0 0 / 0.45), 0 28px 60px -24px rgb(0 0 0 / 0.8);
  --shadow-brand: 0 1px 2px rgb(0 0 0 / 0.5), 0 14px 32px -14px rgb(27 132 243 / 0.5);
}

/* ------------------------------------------------------------------- reset */

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

/* The UA rule for [hidden] is only `display: none`, so any component rule that
   sets `display` beats it — which would leave JS-only controls on screen when
   JavaScript is unavailable. This is the one place !important is correct. */
[hidden] { display: none !important; }

html {
  -webkit-text-size-adjust: 100%;
  scroll-behavior: smooth;
  scroll-padding-top: calc(var(--header-h) + 1.5rem);
}

body {
  margin: 0;
  font-family: var(--font);
  font-size: var(--t-base);
  line-height: 1.65;
  color: var(--ink);
  background: var(--page);
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
  overflow-x: hidden;
}

h1, h2, h3, h4 {
  margin: 0;
  line-height: 1.15;
  letter-spacing: -0.022em;
  font-weight: 750;
}

p { margin: 0; }
ul, ol { margin: 0; padding: 0; }
li { list-style: none; }

a { color: var(--brand-text); text-decoration: none; }
a:hover { color: var(--brand-500); }

img, svg { display: block; max-width: 100%; }
svg { flex: none; }

button, input, textarea, select { font: inherit; color: inherit; }

:focus-visible {
  outline: 3px solid var(--brand-400);
  outline-offset: 2px;
  border-radius: 4px;
}

::selection { background: #b8dcff; color: #0f3a6e; }
:root[data-theme='dark'] ::selection { background: #1d4374; color: #e9f2ff; }

.skip-link {
  position: absolute;
  left: -999px;
  top: 0;
  z-index: 200;
  padding: var(--s-3) var(--s-5);
  background: var(--brand-600);
  color: #fff;
  border-radius: 0 0 var(--radius) 0;
  font-weight: 650;
}
.skip-link:focus { left: 0; color: #fff; }

.visually-hidden {
  position: absolute;
  width: 1px;
  height: 1px;
  margin: -1px;
  padding: 0;
  overflow: hidden;
  clip-path: inset(50%);
  white-space: nowrap;
  border: 0;
}

.shell {
  width: 100%;
  max-width: var(--shell);
  margin-inline: auto;
  padding-inline: var(--s-6);
}

@media (max-width: 640px) {
  .shell { padding-inline: var(--s-5); }
}

/* ----------------------------------------------------------------- header */

.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: color-mix(in srgb, var(--page) 82%, transparent);
  backdrop-filter: saturate(180%) blur(14px);
  -webkit-backdrop-filter: saturate(180%) blur(14px);
  border-bottom: 1px solid transparent;
  transition: border-color 0.25s var(--ease), background 0.25s var(--ease);
}

.site-header.is-stuck {
  border-bottom-color: var(--line);
  background: color-mix(in srgb, var(--page) 92%, transparent);
}

.scroll-progress {
  position: absolute;
  inset: auto 0 -1px 0;
  height: 2px;
  transform-origin: 0 50%;
  transform: scaleX(var(--p, 0));
  background: linear-gradient(90deg, var(--brand-400), var(--cyan), var(--brand-600));
}

.site-header__inner {
  display: flex;
  align-items: center;
  gap: var(--s-6);
  height: var(--header-h);
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: var(--s-3);
  color: var(--ink);
  min-width: 0;
}
.brand:hover { color: var(--ink); }

.brand__mark {
  width: 38px;
  height: 38px;
  flex: none;
  display: block;
  filter: drop-shadow(0 4px 10px rgb(10 82 168 / 0.35));
  transition: transform 0.3s var(--ease);
}
.brand:hover .brand__mark { transform: rotate(-6deg) scale(1.05); }


.brand__name {
  font-weight: 800;
  font-size: 1.18rem;
  letter-spacing: -0.035em;
  white-space: nowrap;
}
.brand__accent { color: var(--brand-500); }

.nav { display: flex; align-items: center; gap: var(--s-1); margin-inline: auto; }

.nav__link {
  position: relative;
  padding: var(--s-2) var(--s-4);
  border-radius: 999px;
  font-size: var(--t-sm);
  font-weight: 620;
  color: var(--ink-2);
  transition: color 0.2s var(--ease), background 0.2s var(--ease);
}
.nav__link:hover { color: var(--brand-text); background: var(--brand-50); }
.nav__link.is-active { color: var(--brand-text); background: var(--brand-100); }

.site-header__actions { display: flex; align-items: center; gap: var(--s-2); flex: none; }

.icon-button {
  display: grid;
  place-items: center;
  width: 38px;
  height: 38px;
  border: 1px solid var(--line);
  border-radius: 11px;
  background: var(--surface);
  color: var(--ink-2);
  cursor: pointer;
  transition: all 0.2s var(--ease);
}
.icon-button svg { width: 18px; height: 18px; }
.icon-button:hover {
  color: var(--brand-text);
  border-color: var(--brand-300);
  background: var(--brand-50);
}

.icon-button__moon { display: none; }
:root[data-theme='dark'] .icon-button__sun { display: none; }
:root[data-theme='dark'] .icon-button__moon { display: block; }

.nav-toggle { display: none; }
.nav-toggle__close { display: none; }

@media (max-width: 900px) {
  .site-header__cta span { display: none; }
  .nav-toggle { display: grid; }

  .nav {
    position: fixed;
    inset: var(--header-h) 0 auto 0;
    flex-direction: column;
    align-items: stretch;
    gap: 0;
    margin: 0;
    padding: var(--s-3);
    background: var(--surface);
    border-bottom: 1px solid var(--line);
    box-shadow: var(--shadow-lg);
    transform: translateY(-8px);
    opacity: 0;
    visibility: hidden;
    transition: all 0.22s var(--ease);
  }
  .nav.is-open { transform: none; opacity: 1; visibility: visible; }
  .nav__link { padding: var(--s-4); border-radius: var(--radius-sm); font-size: var(--t-md); }

  body.nav-open .nav-toggle__open { display: none; }
  body.nav-open .nav-toggle__close { display: block; }
}

/* Below this width the brand subtitle is what has to give, so the icon-only
   controls and the menu toggle all stay on screen. */
@media (max-width: 560px) {
  .site-header__inner { gap: var(--s-3); }
  .brand__name { font-size: 1.05rem; }
}

/* ---------------------------------------------------------------- buttons */

.button {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--s-2);
  padding: 0.72rem 1.3rem;
  border: 1px solid transparent;
  border-radius: 12px;
  font-size: var(--t-sm);
  font-weight: 680;
  letter-spacing: -0.01em;
  cursor: pointer;
  white-space: nowrap;
  transition: transform 0.18s var(--ease), box-shadow 0.18s var(--ease),
              background 0.18s var(--ease), border-color 0.18s var(--ease),
              color 0.18s var(--ease), filter 0.18s var(--ease);
}
.button svg { width: 17px; height: 17px; }
.button:active { transform: translateY(0) scale(0.985); }

.button--primary {
  background: linear-gradient(180deg, var(--brand-500), var(--brand-600));
  color: #fff;
  box-shadow: var(--shadow-brand);
}
.button--primary:hover { color: #fff; filter: brightness(1.07); transform: translateY(-2px); }

.button--ghost {
  background: var(--surface);
  border-color: var(--line-strong);
  color: var(--ink);
}
.button--ghost:hover {
  color: var(--brand-text);
  border-color: var(--brand-300);
  background: var(--brand-50);
  transform: translateY(-2px);
}

.button--invert { background: #fff; color: #0a52a8; box-shadow: var(--shadow); }
.button--invert:hover { color: #0d4485; transform: translateY(-2px); }

.button--outline { border-color: rgb(255 255 255 / 0.45); color: #fff; background: transparent; }
.button--outline:hover { color: #fff; background: rgb(255 255 255 / 0.12); transform: translateY(-2px); }

.button--lg { padding: 0.9rem 1.6rem; font-size: var(--t-md); border-radius: 14px; }
.button--sm { padding: 0.5rem 0.9rem; font-size: var(--t-xs); border-radius: 10px; }

/* ------------------------------------------------------------------ pills */

.pill {
  display: inline-flex;
  align-items: center;
  gap: var(--s-2);
  padding: 0.42rem 0.85rem;
  border-radius: 999px;
  font-size: var(--t-xs);
  font-weight: 650;
  border: 1px solid var(--line);
  background: var(--surface);
  color: var(--ink-2);
  transition: all 0.2s var(--ease);
}
.pill svg { width: 15px; height: 15px; }
.pill--parent { color: var(--brand-text); border-color: var(--brand-200); background: var(--brand-50); }
.pill--parent:hover {
  color: var(--brand-text-strong);
  border-color: var(--brand-300);
  transform: translateY(-1px);
  box-shadow: var(--shadow-sm);
}

.eyebrow {
  display: inline-flex;
  align-items: center;
  gap: var(--s-2);
  font-size: var(--t-xs);
  font-weight: 720;
  letter-spacing: 0.09em;
  text-transform: uppercase;
  color: var(--brand-text);
}
.eyebrow svg { width: 15px; height: 15px; }
.eyebrow--inverse { color: rgb(255 255 255 / 0.85); }

/* ----------------------------------------------------------------- aurora */

.aurora {
  position: absolute;
  inset: -20% -10% auto -10%;
  height: 130%;
  pointer-events: none;
  z-index: 0;
  filter: blur(70px);
  opacity: 0.85;
}
.aurora i {
  position: absolute;
  display: block;
  border-radius: 50%;
  animation: drift 22s var(--ease) infinite alternate;
}
.aurora i:nth-child(1) {
  width: 46vw; height: 46vw; left: -6%; top: 2%;
  background: radial-gradient(circle, rgb(74 165 255 / 0.55), transparent 68%);
}
.aurora i:nth-child(2) {
  width: 38vw; height: 38vw; right: 2%; top: -6%;
  background: radial-gradient(circle, rgb(34 211 238 / 0.4), transparent 68%);
  animation-delay: -6s;
}
.aurora i:nth-child(3) {
  width: 34vw; height: 34vw; left: 34%; top: 42%;
  background: radial-gradient(circle, rgb(124 92 255 / 0.3), transparent 68%);
  animation-delay: -12s;
}
.aurora i:nth-child(4) {
  width: 28vw; height: 28vw; right: 18%; bottom: 2%;
  background: radial-gradient(circle, rgb(133 196 255 / 0.5), transparent 68%);
  animation-delay: -3s;
}
.aurora--sm { height: 100%; inset: -40% -10% auto -10%; filter: blur(60px); opacity: 0.55; }

:root[data-theme='dark'] .aurora { opacity: 0.4; }

/* Track colour as type.
   The cards set --track-color/--track-accent/--track-ink inline, and an inline
   custom property beats any stylesheet rule — so a dark-mode override of
   --track-ink would never apply. Components therefore read --track-text, which
   only this stylesheet defines and the theme is free to switch. */
.track-card, .tutorial-card, .video-card, .track-section,
.jump__item, .marquee__item, .tutorial {
  --track-text: var(--track-ink);
}
:root[data-theme='dark'] .track-card,
:root[data-theme='dark'] .tutorial-card,
:root[data-theme='dark'] .video-card,
:root[data-theme='dark'] .track-section,
:root[data-theme='dark'] .jump__item,
:root[data-theme='dark'] .marquee__item,
:root[data-theme='dark'] .tutorial {
  --track-text: var(--track-accent);
}

@keyframes drift {
  from { transform: translate3d(0, 0, 0) scale(1); }
  to   { transform: translate3d(4%, -6%, 0) scale(1.14); }
}

.grid-overlay {
  position: absolute;
  inset: 0;
  z-index: 0;
  pointer-events: none;
  background-image:
    linear-gradient(to right, color-mix(in srgb, var(--brand-300) 26%, transparent) 1px, transparent 1px),
    linear-gradient(to bottom, color-mix(in srgb, var(--brand-300) 26%, transparent) 1px, transparent 1px);
  background-size: 58px 58px;
  mask-image: radial-gradient(ellipse 90% 62% at 50% 30%, #000 20%, transparent 78%);
  -webkit-mask-image: radial-gradient(ellipse 90% 62% at 50% 30%, #000 20%, transparent 78%);
  opacity: 0.5;
}

/* ------------------------------------------------------------------- hero */

.hero { position: relative; overflow: hidden; padding: var(--s-20) 0 0; }

.hero__inner {
  position: relative;
  z-index: 1;
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: var(--s-12);
  align-items: center;
  padding-bottom: var(--s-16);
}

@media (min-width: 1000px) {
  .hero__inner { grid-template-columns: minmax(0, 1.02fr) minmax(0, 1fr); gap: var(--s-16); }
}

.hero__copy { display: grid; grid-template-columns: minmax(0, 1fr); gap: var(--s-6); justify-items: start; }

.hero__title {
  font-size: var(--t-4xl);
  font-weight: 820;
  letter-spacing: -0.035em;
  line-height: 1.04;
}

.hero__gradient {
  background: linear-gradient(100deg, var(--brand-500) 0%, var(--cyan) 48%, var(--violet) 100%);
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
}

.hero__lead {
  font-size: var(--t-lg);
  color: var(--ink-muted);
  max-width: 34rem;
  line-height: 1.62;
}

.hero__actions { display: flex; flex-wrap: wrap; gap: var(--s-3); }

.hero__points { display: grid;
  grid-template-columns: minmax(0, 1fr); gap: var(--s-2); }
.hero__points li {
  display: flex;
  align-items: center;
  gap: var(--s-2);
  font-size: var(--t-sm);
  color: var(--ink-muted);
}
.hero__points svg { width: 16px; height: 16px; color: var(--brand-500); }

.hero__visual { position: relative; }

.hero__badge {
  position: absolute;
  display: flex;
  align-items: center;
  gap: var(--s-3);
  padding: var(--s-3) var(--s-4);
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  box-shadow: var(--shadow-lg);
  animation: float 6s ease-in-out infinite;
}
.hero__badge svg { width: 20px; height: 20px; color: var(--brand-500); }
.hero__badge strong { display: block; font-size: var(--t-sm); font-weight: 700; }
.hero__badge span { font-size: var(--t-xs); color: var(--ink-muted); }
/* Anchored to the window's outer corners. The panel carries extra bottom
   padding and the tab row stops short of the right edge, so these overlap the
   frame and never the code or the tabs. */
.hero__badge--one { left: -34px; bottom: -26px; }
.hero__badge--two { right: -50px; top: 40px; animation-delay: -3s; }

@media (max-width: 1200px) { .hero__badge { display: none; } }

@keyframes float {
  0%, 100% { transform: translateY(0); }
  50% { transform: translateY(-9px); }
}

/* ---------------------------------------------------------------- marquee */

.marquee {
  position: relative;
  z-index: 1;
  overflow: hidden;
  border-block: 1px solid var(--line);
  background: color-mix(in srgb, var(--surface) 70%, transparent);
  padding: var(--s-4) 0;
  mask-image: linear-gradient(90deg, transparent, #000 8%, #000 92%, transparent);
  -webkit-mask-image: linear-gradient(90deg, transparent, #000 8%, #000 92%, transparent);
}
.marquee__track {
  display: flex;
  gap: var(--s-12);
  width: max-content;
  animation: scroll-x 34s linear infinite;
}
.marquee__item {
  display: inline-flex;
  align-items: center;
  gap: var(--s-3);
  font-size: var(--t-sm);
  font-weight: 700;
  letter-spacing: 0.02em;
  text-transform: uppercase;
  color: var(--ink-faint);
}
.marquee__item svg { width: 20px; height: 20px; color: var(--track-text); }

@keyframes scroll-x {
  from { transform: translateX(0); }
  to { transform: translateX(-50%); }
}

/* --------------------------------------------------------------- sections */

.section { padding: var(--s-24) 0; position: relative; }
.section--alt { background: var(--page-alt); }
.section--stats { padding: var(--s-12) 0; }

.section-head { display: grid;
  grid-template-columns: minmax(0, 1fr); gap: var(--s-4); margin-bottom: var(--s-12); max-width: 46rem; }
.section-head--center { justify-items: center; text-align: center; margin-inline: auto; }
.section-head--left { max-width: none; }
.section-head--left .section-head__lead { max-width: 42rem; }

.section-head__title { font-size: var(--t-3xl); }
.section-head__lead { font-size: var(--t-md); color: var(--ink-muted); line-height: 1.62; }
.section-head--left .button { justify-self: start; margin-top: var(--s-2); }

/* ------------------------------------------------------------------ stats */

.stats {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
  gap: var(--s-4);
  padding: var(--s-8);
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow);
}
.stat { display: grid;
  grid-template-columns: minmax(0, 1fr); gap: var(--s-1); text-align: center; }
.stat__value {
  font-size: var(--t-3xl);
  font-weight: 820;
  letter-spacing: -0.04em;
  background: linear-gradient(160deg, var(--brand-500), var(--brand-700));
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
}
.stat__label { font-size: var(--t-xs); color: var(--ink-muted); font-weight: 600; }

/* ------------------------------------------------------------ track cards */

.track-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(min(100%, 270px), 1fr));
  gap: var(--s-5);
}

.track-card {
  position: relative;
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: var(--s-3);
  padding: var(--s-6);
  overflow: hidden;
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius-lg);
  color: var(--ink);
  box-shadow: var(--shadow-sm);
  transition: transform 0.28s var(--ease), box-shadow 0.28s var(--ease),
              border-color 0.28s var(--ease);
}
.track-card:hover {
  color: var(--ink);
  transform: translateY(-5px);
  border-color: color-mix(in srgb, var(--track-color) 45%, transparent);
  box-shadow: 0 2px 6px rgb(12 28 48 / 0.06),
              0 26px 50px -22px color-mix(in srgb, var(--track-color) 65%, transparent);
}

.track-card__glow {
  position: absolute;
  inset: -60% 40% 60% -30%;
  background: radial-gradient(circle, color-mix(in srgb, var(--track-color) 32%, transparent), transparent 66%);
  filter: blur(34px);
  opacity: 0;
  transition: opacity 0.35s var(--ease);
}
.track-card:hover .track-card__glow { opacity: 1; }

.track-card > *:not(.track-card__glow) { position: relative; z-index: 1; }

.track-card__icon {
  display: grid;
  place-items: center;
  width: 46px;
  height: 46px;
  border-radius: 13px;
  color: #fff;
  background: linear-gradient(150deg, var(--track-accent), var(--track-color));
  box-shadow: 0 8px 18px -8px color-mix(in srgb, var(--track-color) 85%, transparent);
}
.track-card__icon svg { width: 24px; height: 24px; }

.track-card__level {
  position: absolute;
  top: 0;
  right: 0;
  font-size: var(--t-xs);
  font-weight: 650;
  color: var(--ink-faint);
  padding: 0.2rem 0.6rem;
  border: 1px solid var(--line);
  border-radius: 999px;
}
.track-card__name { font-size: var(--t-xl); }
.track-card__tagline { color: var(--ink-muted); font-size: var(--t-sm); line-height: 1.55; }

.track-card__meta {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-top: var(--s-2);
  padding-top: var(--s-4);
  border-top: 1px solid var(--line);
  font-size: var(--t-xs);
  font-weight: 650;
  color: var(--ink-faint);
}
.track-card__go { display: inline-flex; align-items: center; gap: var(--s-2); color: var(--track-text); }
.track-card__go svg { width: 15px; height: 15px; transition: transform 0.25s var(--ease); }
.track-card:hover .track-card__go svg { transform: translateX(4px); }

/* ------------------------------------------------------------------ steps */

.steps {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(min(100%, 260px), 1fr));
  gap: var(--s-5);
}
.step {
  position: relative;
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: var(--s-3);
  padding: var(--s-8) var(--s-6) var(--s-6);
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-sm);
}
.step__n {
  position: absolute;
  top: var(--s-4);
  right: var(--s-5);
  font-size: 2.6rem;
  font-weight: 850;
  letter-spacing: -0.05em;
  color: #2f8ae8;
  opacity: 0.32;
  line-height: 1;
}
.step__icon {
  display: grid;
  place-items: center;
  width: 42px;
  height: 42px;
  border-radius: 12px;
  color: var(--brand-text);
  background: var(--brand-50);
  border: 1px solid var(--brand-100);
}
.step__icon svg { width: 21px; height: 21px; }
.step__title { font-size: var(--t-lg); }
.step__body { color: var(--ink-muted); font-size: var(--t-sm); line-height: 1.6; }

/* ------------------------------------------------------------- card grids */

.card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(min(100%, 320px), 1fr));
  gap: var(--s-5);
}
.card-grid--videos {
  grid-template-columns: repeat(auto-fill, minmax(min(100%, 300px), 1fr));
}

/* --------------------------------------------------------- tutorial cards */

.tutorial-card {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-sm);
  overflow: hidden;
  transition: transform 0.26s var(--ease), box-shadow 0.26s var(--ease),
              border-color 0.26s var(--ease);
}
.tutorial-card:hover {
  transform: translateY(-4px);
  border-color: color-mix(in srgb, var(--track-color) 42%, transparent);
  box-shadow: 0 2px 6px rgb(12 28 48 / 0.06),
              0 24px 46px -22px color-mix(in srgb, var(--track-color) 60%, transparent);
}

.tutorial-card__link {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: var(--s-3);
  align-content: start;
  height: 100%;
  padding: var(--s-6);
  color: var(--ink);
  border-top: 3px solid var(--track-color);
}
.tutorial-card__link:hover { color: var(--ink); }

.tutorial-card__top {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--s-3);
  font-size: var(--t-xs);
  font-weight: 650;
  color: var(--ink-faint);
}
.tutorial-card__track { display: inline-flex; align-items: center; gap: var(--s-2); color: var(--track-text); }
.tutorial-card__track svg { width: 17px; height: 17px; }
.tutorial-card__time { display: inline-flex; align-items: center; gap: 5px; }
.tutorial-card__time svg { width: 14px; height: 14px; }

.tutorial-card__title { font-size: var(--t-lg); line-height: 1.28; }
.tutorial-card__summary { font-size: var(--t-sm); color: var(--ink-muted); line-height: 1.58; }

.tutorial-card__foot {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-top: auto;
  padding-top: var(--s-4);
  border-top: 1px solid var(--line);
  font-size: var(--t-xs);
  font-weight: 650;
}
.tutorial-card__level {
  padding: 0.18rem 0.55rem;
  border-radius: 999px;
  background: var(--brand-50);
  color: var(--brand-text);
  border: 1px solid var(--brand-100);
}
.tutorial-card__go { display: inline-flex; align-items: center; gap: 6px; color: var(--track-text); }
.tutorial-card__go svg { width: 15px; height: 15px; transition: transform 0.25s var(--ease); }
.tutorial-card:hover .tutorial-card__go svg { transform: translateX(4px); }

/* ------------------------------------------------------------ video cards */

.video-card {
  display: grid;
  grid-template-rows: auto 1fr;
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius-lg);
  overflow: hidden;
  box-shadow: var(--shadow-sm);
  transition: transform 0.26s var(--ease), box-shadow 0.26s var(--ease),
              border-color 0.26s var(--ease);
}
.video-card:hover {
  transform: translateY(-4px);
  border-color: color-mix(in srgb, var(--track-color) 42%, transparent);
  box-shadow: 0 2px 6px rgb(12 28 48 / 0.06),
              0 24px 46px -22px color-mix(in srgb, var(--track-color) 60%, transparent);
}

.video-card__thumb {
  position: relative;
  display: block;
  aspect-ratio: 16 / 9;
  overflow: hidden;
  background: var(--code-bg);
}
.video-card__img { width: 100%; height: 100%; object-fit: cover; }

.video-card__art {
  position: absolute;
  inset: 0;
  display: grid;
  place-items: center;
  background:
    radial-gradient(120% 90% at 20% 10%, color-mix(in srgb, var(--track-accent) 55%, transparent), transparent 60%),
    linear-gradient(150deg, var(--track-color), color-mix(in srgb, var(--track-color) 40%, var(--code-bg)));
}
.video-card__art::after {
  content: '';
  position: absolute;
  inset: 0;
  background-image:
    linear-gradient(to right, rgb(255 255 255 / 0.09) 1px, transparent 1px),
    linear-gradient(to bottom, rgb(255 255 255 / 0.09) 1px, transparent 1px);
  background-size: 26px 26px;
}
.video-card__art-glyph { color: #fff; opacity: 0.95; }
.video-card__art-glyph svg { width: 54px; height: 54px; }
.video-card__art-index {
  position: absolute;
  left: var(--s-4);
  top: var(--s-3);
  font-size: var(--t-xs);
  font-weight: 800;
  letter-spacing: 0.12em;
  color: rgb(255 255 255 / 0.72);
}

.video-card__play {
  position: absolute;
  inset: 0;
  margin: auto;
  width: 54px;
  height: 54px;
  display: grid;
  place-items: center;
  border-radius: 50%;
  background: rgb(255 255 255 / 0.94);
  color: #ff0033;
  box-shadow: 0 10px 26px rgb(0 0 0 / 0.32);
  opacity: 0;
  transform: scale(0.8);
  transition: all 0.26s var(--ease);
}
.video-card__play svg { width: 26px; height: 26px; margin-left: 2px; }
.video-card__thumb:hover .video-card__play,
.video-card__thumb:focus-visible .video-card__play { opacity: 1; transform: scale(1); }

.video-card__duration {
  position: absolute;
  right: var(--s-3);
  bottom: var(--s-3);
  padding: 0.15rem 0.45rem;
  border-radius: 6px;
  background: rgb(8 17 31 / 0.85);
  color: #fff;
  font-size: var(--t-xs);
  font-weight: 650;
  font-variant-numeric: tabular-nums;
}

.video-card__body { display: grid;
  grid-template-columns: minmax(0, 1fr); gap: var(--s-2); align-content: start; padding: var(--s-5); }
.video-card__series {
  font-size: var(--t-xs);
  font-weight: 700;
  letter-spacing: 0.05em;
  text-transform: uppercase;
  color: var(--track-text);
}
.video-card__title { font-size: var(--t-md); line-height: 1.32; }
.video-card__title a { color: var(--ink); }
.video-card__title a:hover { color: var(--brand-text); }
.video-card__summary { font-size: var(--t-sm); color: var(--ink-muted); line-height: 1.55; }

.video-card__foot {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--s-3);
  margin-top: var(--s-2);
  padding-top: var(--s-3);
  border-top: 1px solid var(--line);
  font-size: var(--t-xs);
}
.video-card__views { color: var(--ink-faint); font-weight: 600; }
.video-card__read { display: inline-flex; align-items: center; gap: 5px; font-weight: 680; }
.video-card__read svg { width: 14px; height: 14px; transition: transform 0.25s var(--ease); }
.video-card__read:hover svg { transform: translateX(3px); }

/* ------------------------------------------------------------------- CTAs */

.cta {
  position: relative;
  overflow: hidden;
  padding: var(--s-16) var(--s-8);
  border-radius: var(--radius-xl);
  background: linear-gradient(135deg, var(--brand-700), var(--brand-500) 55%, var(--cyan) 130%);
  color: #fff;
  box-shadow: var(--shadow-lg);
}
.cta__glow {
  position: absolute;
  inset: -50% -20% auto -20%;
  height: 160%;
  background: radial-gradient(circle at 30% 25%, rgb(255 255 255 / 0.28), transparent 55%);
}
.cta__body { position: relative; display: grid; gap: var(--s-4); justify-items: center; text-align: center; }
.cta__title { font-size: var(--t-3xl); }
.cta__lead { max-width: 44rem; color: rgb(255 255 255 / 0.9); font-size: var(--t-md); }
.cta__actions { display: flex; flex-wrap: wrap; gap: var(--s-3); justify-content: center; margin-top: var(--s-2); }

/* -------------------------------------------------------------- page hero */

.page-hero { position: relative; overflow: hidden; padding: var(--s-20) 0 var(--s-12); }
.page-hero .shell {
  position: relative;
  z-index: 1;
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: var(--s-4);
}
.page-hero--center .shell { justify-items: center; text-align: center; }
.page-hero__title { font-size: clamp(2.1rem, 4.6vw, 3.2rem); letter-spacing: -0.035em; }
.page-hero__title code {
  font-family: var(--mono);
  font-size: 0.82em;
  padding: 0.08em 0.3em;
  border-radius: 8px;
  background: var(--brand-50);
  color: var(--brand-text);
  border: 1px solid var(--brand-100);
}
.page-hero__lead { font-size: var(--t-lg); color: var(--ink-muted); max-width: 46rem; }
.page-hero__actions { display: flex; flex-wrap: wrap; gap: var(--s-3); margin-top: var(--s-2); }

.jump { display: flex; flex-wrap: wrap; gap: var(--s-2); margin-top: var(--s-2); }
.jump__item {
  display: inline-flex;
  align-items: center;
  gap: var(--s-2);
  padding: 0.45rem 0.85rem;
  border-radius: 999px;
  border: 1px solid var(--line);
  background: var(--surface);
  color: var(--ink-2);
  font-size: var(--t-sm);
  font-weight: 640;
  transition: all 0.2s var(--ease);
}
.jump__item svg { width: 17px; height: 17px; color: var(--track-color); }
.jump__item:hover {
  color: var(--ink);
  transform: translateY(-2px);
  border-color: color-mix(in srgb, var(--track-color) 50%, transparent);
  box-shadow: var(--shadow-sm);
}

/* ----------------------------------------------------------- filter bar */

.filter-bar {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: var(--s-4);
  margin-bottom: var(--s-8);
  padding: var(--s-4);
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-sm);
  position: sticky;
  top: calc(var(--header-h) + 8px);
  z-index: 20;
}

.search { position: relative; display: flex; align-items: center; flex: 1 1 15rem; }
.search__icon {
  position: absolute;
  left: var(--s-3);
  display: grid;
  place-items: center;
  color: var(--ink-faint);
  pointer-events: none;
}
.search__icon svg { width: 17px; height: 17px; }
.search input {
  width: 100%;
  padding: 0.6rem 0.9rem 0.6rem 2.4rem;
  border: 1.5px solid var(--line);
  border-radius: 11px;
  background: var(--surface-2);
  font-size: var(--t-sm);
  transition: all 0.18s var(--ease);
}
.search input::placeholder { color: var(--ink-faint); }
.search input:focus {
  outline: none;
  background: var(--surface);
  border-color: var(--brand-400);
  box-shadow: 0 0 0 4px color-mix(in srgb, var(--brand-400) 20%, transparent);
}

.chips { display: flex; flex-wrap: wrap; gap: var(--s-2); }
.chip {
  display: inline-flex;
  align-items: center;
  gap: var(--s-2);
  padding: 0.44rem 0.85rem;
  border: 1px solid var(--line);
  border-radius: 999px;
  background: var(--surface-2);
  color: var(--ink-2);
  font-size: var(--t-sm);
  font-weight: 640;
  cursor: pointer;
  transition: all 0.18s var(--ease);
}
.chip:hover { border-color: var(--brand-300); color: var(--brand-text); background: var(--brand-50); }
.chip.is-active {
  color: #fff;
  border-color: transparent;
  background: var(--chip-color, var(--brand-600));
  box-shadow: 0 6px 14px -8px var(--chip-color, var(--brand-600));
}
.chip__count {
  font-size: var(--t-xs);
  font-weight: 700;
  padding: 0 0.35rem;
  border-radius: 999px;
  background: color-mix(in srgb, currentColor 16%, transparent);
}

.filter-empty {
  padding: var(--s-12) var(--s-6);
  text-align: center;
  color: var(--ink-muted);
  border: 1px dashed var(--line-strong);
  border-radius: var(--radius-lg);
  margin-bottom: var(--s-8);
}

@media (max-width: 720px) {
  .filter-bar { position: static; }
}

/* --------------------------------------------------------- track sections */

.track-sections {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: var(--s-12);
  padding-bottom: var(--s-24);
}

.track-section {
  position: relative;
  padding: var(--s-8);
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius-xl);
  box-shadow: var(--shadow-sm);
  scroll-margin-top: calc(var(--header-h) + 1.5rem);
  overflow: hidden;
}
.track-section::before {
  content: '';
  position: absolute;
  inset: 0 0 auto 0;
  height: 4px;
  background: linear-gradient(90deg, var(--track-color), var(--track-accent));
}

.track-section__head { display: flex; gap: var(--s-5); align-items: flex-start; margin-bottom: var(--s-8); }
.track-section__icon {
  display: grid;
  place-items: center;
  width: 58px;
  height: 58px;
  flex: none;
  border-radius: 16px;
  color: #fff;
  background: linear-gradient(150deg, var(--track-accent), var(--track-color));
  box-shadow: 0 10px 24px -10px color-mix(in srgb, var(--track-color) 85%, transparent);
}
.track-section__icon svg { width: 30px; height: 30px; }
.track-section__level {
  font-size: var(--t-xs);
  font-weight: 700;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--ink-faint);
}
.track-section__name { font-size: var(--t-2xl); margin: var(--s-1) 0 var(--s-2); }
.track-section__blurb { color: var(--ink-muted); max-width: 46rem; line-height: 1.6; }

.track-section__grid { display: grid; grid-template-columns: minmax(0, 1fr); gap: var(--s-8); }
@media (min-width: 900px) {
  .track-section__grid { grid-template-columns: minmax(0, 1.6fr) minmax(0, 1fr); }
}

.track-section__sub {
  display: flex;
  align-items: center;
  gap: var(--s-2);
  font-size: var(--t-xs);
  font-weight: 720;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--ink-faint);
  margin-bottom: var(--s-4);
}
.track-section__sub svg { width: 16px; height: 16px; color: var(--track-color); }

.syllabus { display: grid; grid-template-columns: minmax(0, 1fr); gap: var(--s-2); }
.syllabus__row a {
  display: grid;
  grid-template-columns: auto minmax(0, 1fr) auto auto;
  align-items: center;
  gap: var(--s-4);
  padding: var(--s-4);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--surface-2);
  color: var(--ink);
  transition: all 0.2s var(--ease);
}
.syllabus__row a:hover {
  color: var(--ink);
  transform: translateX(4px);
  border-color: color-mix(in srgb, var(--track-color) 45%, transparent);
  background: var(--surface);
  box-shadow: var(--shadow-sm);
}
.syllabus__n {
  font-family: var(--mono);
  font-size: var(--t-sm);
  font-weight: 700;
  color: var(--track-text);
}
.syllabus__body { display: grid;
  grid-template-columns: minmax(0, 1fr); gap: 2px; min-width: 0; }
.syllabus__title { font-weight: 660; font-size: var(--t-md); }
.syllabus__summary {
  font-size: var(--t-sm);
  color: var(--ink-muted);
  line-height: 1.5;
  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow: hidden;
}
.syllabus__time {
  display: inline-flex;
  align-items: center;
  gap: 5px;
  font-size: var(--t-xs);
  font-weight: 640;
  color: var(--ink-faint);
  white-space: nowrap;
}
.syllabus__time svg { width: 14px; height: 14px; }
.syllabus__go svg { width: 18px; height: 18px; color: var(--ink-faint); }
.syllabus__empty { padding: var(--s-6); color: var(--ink-muted); font-size: var(--t-sm); }

@media (max-width: 620px) {
  .syllabus__row a { grid-template-columns: auto minmax(0, 1fr); gap: var(--s-3); }
  .syllabus__time, .syllabus__go { display: none; }
}

@media (max-width: 560px) {
  .track-section { padding: var(--s-5); }
  .cta { padding: var(--s-10) var(--s-5); }
  .stats { padding: var(--s-5); }
  .about-card, .principle, .step, .parent-card { padding: var(--s-5); }
  .code-block pre, .code-window__panel { padding: var(--s-4); font-size: 0.79rem; }
}

.video-list { display: grid; grid-template-columns: minmax(0, 1fr); gap: var(--s-1); }
.video-list a {
  display: flex;
  align-items: center;
  gap: var(--s-3);
  padding: var(--s-3);
  border-radius: var(--radius-sm);
  color: var(--ink-2);
  font-size: var(--t-sm);
  transition: all 0.18s var(--ease);
}
.video-list a:hover { background: var(--brand-50); color: var(--brand-text); }
.video-list svg { width: 16px; height: 16px; color: var(--track-color); }
.video-list span {
  flex: 1;
  min-width: 0;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}
.video-list em {
  font-style: normal;
  font-size: var(--t-xs);
  font-variant-numeric: tabular-nums;
  color: var(--ink-faint);
}

/* --------------------------------------------------------------- tutorial */

.reading-progress {
  position: fixed;
  inset: 0 0 auto 0;
  height: 3px;
  z-index: 110;
  pointer-events: none;
}
.reading-progress i {
  display: block;
  height: 100%;
  width: 100%;
  transform-origin: 0 50%;
  transform: scaleX(var(--p, 0));
  background: linear-gradient(90deg, var(--brand-400), var(--cyan));
}

.tutorial__hero { position: relative; overflow: hidden; padding: var(--s-12) 0 var(--s-10); }
.tutorial__hero .shell {
  position: relative;
  z-index: 1;
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: var(--s-4);
}

.crumbs {
  display: flex;
  align-items: center;
  gap: var(--s-2);
  font-size: var(--t-sm);
  color: var(--ink-faint);
}
.crumbs svg { width: 14px; height: 14px; }
.crumbs a { color: var(--ink-muted); font-weight: 620; }
.crumbs a:hover { color: var(--brand-text); }

.tutorial__title { font-size: clamp(2rem, 4.4vw, 3rem); max-width: 22ch; }
.tutorial__summary { font-size: var(--t-lg); color: var(--ink-muted); max-width: 46rem; line-height: 1.6; }

.tutorial__meta { display: flex; flex-wrap: wrap; gap: var(--s-2); margin-top: var(--s-2); }
.tutorial__badge {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 0.4rem 0.8rem;
  border-radius: 999px;
  border: 1px solid var(--line);
  background: var(--surface);
  font-size: var(--t-xs);
  font-weight: 650;
  color: var(--ink-2);
}
.tutorial__badge svg { width: 15px; height: 15px; }
.tutorial__badge--track { color: var(--track-text); border-color: color-mix(in srgb, var(--track-color) 35%, transparent); }
.tutorial__badge--video { color: #fff; background: #ff0033; border-color: transparent; }
.tutorial__badge--video:hover { color: #fff; filter: brightness(1.08); }

.tutorial__layout {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: var(--s-10);
  padding-bottom: var(--s-24);
}

@media (min-width: 1000px) {
  .tutorial__layout { grid-template-columns: 15.5rem minmax(0, 1fr); gap: var(--s-12); }
}

.tutorial__toc { display: none; }
@media (min-width: 1000px) { .tutorial__toc { display: block; } }

.toc {
  position: sticky;
  top: calc(var(--header-h) + var(--s-6));
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: var(--s-3);
}
.toc__title {
  display: flex;
  align-items: center;
  gap: var(--s-2);
  font-size: var(--t-xs);
  font-weight: 720;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--ink-faint);
}
.toc__title svg { width: 15px; height: 15px; }
.toc__list { display: grid;
  grid-template-columns: minmax(0, 1fr); gap: 1px; border-left: 2px solid var(--line); }
.toc__list a {
  display: block;
  padding: 0.4rem var(--s-4);
  margin-left: -2px;
  border-left: 2px solid transparent;
  font-size: var(--t-sm);
  line-height: 1.42;
  color: var(--ink-muted);
  transition: all 0.18s var(--ease);
}
.toc__list a:hover { color: var(--brand-text); border-left-color: var(--brand-300); }
.toc__list a.is-active {
  color: var(--track-text);
  border-left-color: var(--track-color);
  font-weight: 660;
}

.toc__video {
  display: flex;
  align-items: center;
  gap: var(--s-3);
  margin-top: var(--s-4);
  padding: var(--s-4);
  border-radius: var(--radius);
  border: 1px solid var(--line);
  background: var(--surface);
  color: var(--ink);
  transition: all 0.2s var(--ease);
}
.toc__video:hover { color: var(--ink); border-color: var(--brand-300); box-shadow: var(--shadow-sm); transform: translateY(-2px); }
.toc__video svg { width: 20px; height: 20px; color: #ff0033; }
.toc__video strong { display: block; font-size: var(--t-sm); }
.toc__video em { font-style: normal; font-size: var(--t-xs); color: var(--ink-muted); }

/* ------------------------------------------------------------------ prose */

.prose { max-width: 46rem; font-size: var(--t-md); line-height: 1.75; color: var(--ink-2); }
.prose > * + * { margin-top: var(--s-5); }

.prose h2 {
  position: relative;
  font-size: var(--t-2xl);
  margin-top: var(--s-16);
  padding-top: var(--s-2);
  color: var(--ink);
  scroll-margin-top: calc(var(--header-h) + 1.5rem);
}
.prose h3 {
  font-size: var(--t-lg);
  margin-top: var(--s-10);
  color: var(--ink);
  scroll-margin-top: calc(var(--header-h) + 1.5rem);
}
.prose h4 { font-size: var(--t-md); margin-top: var(--s-8); color: var(--ink); }

.heading-anchor {
  position: absolute;
  left: -1.4rem;
  color: var(--brand-text);
  opacity: 0;
  font-weight: 600;
  transition: opacity 0.18s var(--ease);
}
.prose h2:hover .heading-anchor { opacity: 1; }
@media (max-width: 1000px) { .heading-anchor { display: none; } }

.prose strong { color: var(--ink); font-weight: 680; }

.prose ul, .prose ol {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: var(--s-2);
  padding-left: var(--s-6);
}
.prose li { list-style: disc; }
.prose ol li { list-style: decimal; }
.prose li::marker { color: var(--brand-400); }

.prose ul.task-list { padding-left: 0; }
.prose .task { display: flex; gap: var(--s-3); align-items: flex-start; list-style: none; }
.task__box {
  flex: none;
  width: 18px;
  height: 18px;
  margin-top: 4px;
  border: 2px solid var(--line-strong);
  border-radius: 5px;
}
.task.is-done .task__box {
  background: var(--brand-500);
  border-color: var(--brand-500);
}

.prose :not(pre) > code {
  font-family: var(--mono);
  font-size: 0.855em;
  padding: 0.16em 0.4em;
  border-radius: 6px;
  background: var(--brand-50);
  border: 1px solid var(--brand-100);
  color: var(--brand-text-strong);
  word-break: break-word;
}

.prose a { font-weight: 620; text-decoration: underline; text-underline-offset: 3px; text-decoration-thickness: 1.5px; text-decoration-color: var(--brand-300); }
.prose a:hover { text-decoration-color: var(--brand-500); }

.prose hr { border: none; border-top: 1px solid var(--line); margin-block: var(--s-10); }

/* ------------------------------------------------------------------ table */

.table-wrap {
  overflow-x: auto;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--surface);
  box-shadow: var(--shadow-sm);
}
.prose table { width: 100%; border-collapse: collapse; font-size: var(--t-sm); }
.prose th, .prose td { padding: var(--s-3) var(--s-4); text-align: left; vertical-align: top; }
.prose thead th {
  background: var(--surface-3);
  font-weight: 700;
  color: var(--ink);
  font-size: var(--t-xs);
  letter-spacing: 0.05em;
  text-transform: uppercase;
  white-space: nowrap;
}
.prose tbody tr + tr { border-top: 1px solid var(--line); }
.prose tbody tr:hover { background: var(--surface-2); }
.prose td code { white-space: nowrap; }

/* --------------------------------------------------------------- callouts */

.callout {
  --c: var(--brand-500);
  --c-bg: var(--brand-50);
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: var(--s-2);
  padding: var(--s-5);
  border-radius: var(--radius);
  border: 1px solid color-mix(in srgb, var(--c) 28%, transparent);
  border-left: 3px solid var(--c);
  background: var(--c-bg);
}
.callout__title {
  display: flex;
  align-items: center;
  gap: var(--s-2);
  font-weight: 700;
  color: var(--c);
  font-size: var(--t-sm);
  letter-spacing: 0.01em;
}
.callout__icon { width: 18px; height: 18px; flex: none; }
.callout__body { font-size: var(--t-sm); line-height: 1.68; }
.callout__body > * + * { margin-top: var(--s-3); }
.callout__body p { color: var(--ink-2); }
.callout__body ul, .callout__body ol { display: grid; gap: var(--s-1); padding-left: var(--s-5); }
.callout__body li { list-style: disc; }
.callout__body ol li { list-style: decimal; }
.callout__body :not(pre) > code {
  font-family: var(--mono);
  font-size: 0.86em;
  padding: 0.14em 0.36em;
  border-radius: 5px;
  background: color-mix(in srgb, var(--c) 12%, transparent);
  border: 1px solid color-mix(in srgb, var(--c) 22%, transparent);
  color: inherit;
}

.callout--note { --c: #2f7ff0; --c-bg: color-mix(in srgb, #2f7ff0 7%, var(--surface)); }
.callout--tip { --c: #0f9d76; --c-bg: color-mix(in srgb, #0f9d76 8%, var(--surface)); }
.callout--warning { --c: #d97706; --c-bg: color-mix(in srgb, #d97706 9%, var(--surface)); }
.callout--gotcha { --c: #e0484d; --c-bg: color-mix(in srgb, #e0484d 8%, var(--surface)); }
.callout--challenge { --c: var(--violet); --c-bg: color-mix(in srgb, #7c5cff 9%, var(--surface)); }

/* ------------------------------------------------------------- code block */

.code-block {
  border-radius: var(--radius);
  overflow: hidden;
  background: var(--code-bg);
  border: 1px solid var(--code-line);
  box-shadow: var(--shadow);
}
.code-block__bar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0.4rem 0.5rem 0.4rem var(--s-4);
  background: var(--code-bg-2);
  border-bottom: 1px solid var(--code-line);
}
.code-block__lang {
  font-family: var(--mono);
  font-size: var(--t-xs);
  font-weight: 600;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: #7b96ba;
}
.code-block__copy {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 0.28rem 0.6rem;
  border: 1px solid transparent;
  border-radius: 7px;
  background: transparent;
  color: #8aa5c9;
  font-size: var(--t-xs);
  font-weight: 640;
  cursor: pointer;
  transition: all 0.18s var(--ease);
}
.code-block__copy:hover { color: #d5e5fb; background: rgb(255 255 255 / 0.07); border-color: rgb(255 255 255 / 0.12); }
.code-block__copy.is-copied { color: #4ade80; }

.code-block pre {
  margin: 0;
  padding: var(--s-5);
  overflow-x: auto;
  font-family: var(--mono);
  font-size: 0.845rem;
  line-height: 1.72;
  color: var(--code-ink);
  tab-size: 4;
}
.code-block code { font-family: inherit; }

/* -------------------------------------------------------------- code window */

.code-window {
  position: relative;
  border-radius: var(--radius-lg);
  overflow: hidden;
  background: var(--code-bg);
  border: 1px solid var(--code-line);
  box-shadow: var(--shadow-lg), 0 0 0 1px rgb(255 255 255 / 0.04) inset;
}
.code-window__chrome {
  display: flex;
  align-items: center;
  gap: var(--s-4);
  padding: var(--s-3) var(--s-4);
  background: var(--code-bg-2);
  border-bottom: 1px solid var(--code-line);
}
.code-window__dots { display: flex; gap: 6px; flex: none; }
.code-window__dots i { width: 11px; height: 11px; border-radius: 50%; background: #2c4468; }
.code-window__dots i:nth-child(1) { background: #ff5f57; }
.code-window__dots i:nth-child(2) { background: #febc2e; }
.code-window__dots i:nth-child(3) { background: #28c840; }

.code-window__tabs { display: flex; gap: 2px; overflow-x: auto; }
.code-window__tab {
  padding: 0.3rem 0.75rem;
  border: none;
  border-radius: 7px;
  background: transparent;
  color: #7b96ba;
  font-family: var(--mono);
  font-size: var(--t-xs);
  font-weight: 600;
  cursor: pointer;
  white-space: nowrap;
  transition: all 0.18s var(--ease);
}
.code-window__tab:hover { color: #b9d0ec; background: rgb(255 255 255 / 0.05); }
.code-window__tab.is-active { color: #e8f2ff; background: rgb(74 165 255 / 0.18); }

.code-window__body { position: relative; }
.code-window__panel {
  margin: 0;
  padding: var(--s-5) var(--s-6) var(--s-16);
  min-height: 23rem;
  overflow-x: auto;
  font-family: var(--mono);
  font-size: 0.83rem;
  line-height: 1.75;
  color: var(--code-ink);
  tab-size: 4;
}
.code-window__panel code { display: grid; }

.cw-line { display: block; min-height: 1.75em; }
.code-window--animated .code-window__panel.is-active .cw-line {
  opacity: 0;
  animation: line-in 0.42s var(--ease) forwards;
  animation-delay: calc(var(--i) * 55ms + 180ms);
}
@keyframes line-in {
  from { opacity: 0; transform: translateY(6px); }
  to { opacity: 1; transform: none; }
}

/* ------------------------------------------------------- syntax highlighting */

.tok-comment { color: #7291b2; font-style: italic; }
.tok-string { color: #7ee0a8; }
.tok-keyword { color: #6cb8ff; font-weight: 600; }
.tok-constant { color: #f0a674; }
.tok-builtin { color: #67d9e8; }
.tok-number { color: #f2b8c6; }
.tok-function { color: #b9a6ff; }
.tok-operator { color: #8ba7c9; }
.tok-variable { color: #ffb38a; }
.tok-decorator { color: #b9a6ff; }
.tok-symbol { color: #f0a674; }
.tok-tag { color: #ff8fa3; font-weight: 600; }
.tok-lang { color: #ff8fa3; font-weight: 600; }
.tok-type { color: #67d9e8; }
.tok-preprocessor { color: #64809f; }
.tok-doctype { color: #64809f; }
.tok-phptag { color: #ff8fa3; }
.tok-attr { color: #f0a674; }
.tok-atrule { color: #6cb8ff; font-weight: 600; }
.tok-property { color: #67d9e8; }
.tok-selector { color: #b9a6ff; }
.tok-regex { color: #7ee0a8; }
.tok-flag { color: #f0a674; }

/* -------------------------------------------------------------- tutorial end */

.tutorial__end { margin-top: var(--s-16); }
.tutorial__end-card {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: var(--s-3);
  padding: var(--s-8);
  border-radius: var(--radius-lg);
  background: linear-gradient(140deg, var(--brand-50), var(--surface));
  border: 1px solid var(--brand-100);
}
.tutorial__end-card h2 { font-size: var(--t-xl); margin: 0; color: var(--ink); }
.tutorial__end-card p { color: var(--ink-muted); font-size: var(--t-sm); }
.tutorial__end-actions { display: flex; flex-wrap: wrap; gap: var(--s-3); margin-top: var(--s-2); }

.pager {
  display: grid;
  gap: var(--s-4);
  margin-top: var(--s-8);
  grid-template-columns: minmax(0, 1fr) minmax(0, 1fr);
}
.pager__link {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 4px;
  padding: var(--s-5);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--surface);
  color: var(--ink);
  transition: all 0.2s var(--ease);
}
.pager__link:hover {
  color: var(--ink);
  border-color: var(--brand-300);
  box-shadow: var(--shadow-sm);
  transform: translateY(-2px);
}
.pager__link--next { text-align: right; }
.pager__dir {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  font-size: var(--t-xs);
  font-weight: 700;
  letter-spacing: 0.07em;
  text-transform: uppercase;
  color: var(--ink-faint);
}
.pager__link--next .pager__dir { justify-content: flex-end; }
.pager__dir svg { width: 14px; height: 14px; }
.pager__title { font-weight: 660; font-size: var(--t-sm); line-height: 1.4; }

@media (max-width: 620px) {
  .pager { grid-template-columns: minmax(0, 1fr); }
  .pager__link--next { text-align: left; }
  .pager__link--next .pager__dir { justify-content: flex-start; }
}

/* ------------------------------------------------------------------ about */

.about-grid {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: var(--s-8);
  padding-block: var(--s-4);
  align-items: start;
}
@media (min-width: 860px) { .about-grid { grid-template-columns: 20rem minmax(0, 1fr); gap: var(--s-12); } }
.page-about .section { padding: var(--s-16) 0; }

.about-card {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: var(--s-3);
  justify-items: start;
  align-content: start;
  padding: var(--s-8);
  border-radius: var(--radius-lg);
  background: var(--surface);
  border: 1px solid var(--line);
  box-shadow: var(--shadow);
  position: sticky;
  top: calc(var(--header-h) + var(--s-6));
}
.about-card__avatar {
  display: grid;
  place-items: center;
  width: 64px;
  height: 64px;
  border-radius: 18px;
  color: #fff;
  background: linear-gradient(150deg, var(--brand-400), var(--brand-700));
  box-shadow: var(--shadow-brand);
}
.about-card__avatar svg { width: 30px; height: 30px; }
.about-card h2 { font-size: var(--t-2xl); }
.about-card__role { font-size: var(--t-sm); color: var(--ink-muted); }
.about-card__links { display: flex; flex-wrap: wrap; gap: var(--s-2); margin-top: var(--s-2); }

@media (max-width: 859px) { .about-card { position: static; } }

.about-bio { max-width: none; }

.principles { display: grid; grid-template-columns: repeat(auto-fit, minmax(min(100%, 260px), 1fr)); gap: var(--s-5); }
.principle {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: var(--s-3);
  padding: var(--s-6);
  border-radius: var(--radius-lg);
  background: var(--surface);
  border: 1px solid var(--line);
  box-shadow: var(--shadow-sm);
}
.principle__icon {
  display: grid;
  place-items: center;
  width: 42px;
  height: 42px;
  border-radius: 12px;
  color: var(--brand-text);
  background: var(--brand-50);
  border: 1px solid var(--brand-100);
}
.principle__icon svg { width: 21px; height: 21px; }
.principle h3 { font-size: var(--t-lg); }
.principle p { color: var(--ink-muted); font-size: var(--t-sm); line-height: 1.6; }

.parent-card {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: var(--s-5);
  align-items: center;
  padding: var(--s-8);
  border-radius: var(--radius-xl);
  background: linear-gradient(135deg, var(--brand-700), var(--brand-500));
  color: #fff;
  box-shadow: var(--shadow-lg);
}
@media (min-width: 720px) { .parent-card { grid-template-columns: auto minmax(0, 1fr); gap: var(--s-8); } }
.parent-card__mark {
  display: grid;
  place-items: center;
  width: 76px;
  height: 76px;
  border-radius: 22px;
  background: rgb(255 255 255 / 0.16);
  border: 1px solid rgb(255 255 255 / 0.25);
}
.parent-card__mark svg { width: 38px; height: 38px; }
.parent-card h2 { font-size: var(--t-2xl); margin-bottom: var(--s-2); }
.parent-card p { color: rgb(255 255 255 / 0.9); margin-bottom: var(--s-5); max-width: 44rem; }

.colophon { max-width: 48rem; margin-inline: auto; }

.note-card {
  display: flex;
  gap: var(--s-4);
  align-items: flex-start;
  margin: var(--s-12) 0 var(--s-24);
  padding: var(--s-6);
  border-radius: var(--radius-lg);
  border: 1px dashed var(--line-strong);
  background: var(--surface-2);
}
.note-card > svg { width: 22px; height: 22px; color: var(--brand-500); flex: none; margin-top: 2px; }
.note-card h2 { font-size: var(--t-lg); margin-bottom: var(--s-2); }
.note-card p { color: var(--ink-muted); font-size: var(--t-sm); line-height: 1.6; max-width: 52rem; }
.note-card code {
  font-family: var(--mono);
  font-size: 0.86em;
  padding: 0.12em 0.35em;
  border-radius: 5px;
  background: var(--brand-50);
  border: 1px solid var(--brand-100);
  color: var(--brand-text-strong);
}

/* ----------------------------------------------------------------- footer */

.site-footer {
  margin-top: auto;
  padding: var(--s-16) 0 var(--s-8);
  background: var(--page-alt);
  border-top: 1px solid var(--line);
}
.site-footer__grid { display: grid; grid-template-columns: minmax(0, 1fr); gap: var(--s-10); }
@media (min-width: 860px) {
  .site-footer__grid { grid-template-columns: minmax(0, 1.6fr) repeat(3, minmax(0, 1fr)); gap: var(--s-8); }
}
.site-footer__brand { display: grid;
  grid-template-columns: minmax(0, 1fr); gap: var(--s-4); justify-items: start; }
.site-footer__blurb { color: var(--ink-muted); font-size: var(--t-sm); max-width: 30rem; line-height: 1.6; }
.site-footer__heading {
  font-size: var(--t-xs);
  font-weight: 720;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--ink-faint);
  margin-bottom: var(--s-3);
}
.site-footer__col ul { display: grid;
  grid-template-columns: minmax(0, 1fr); gap: var(--s-2); }
.site-footer__col a { color: var(--ink-muted); font-size: var(--t-sm); }
.site-footer__col a:hover { color: var(--brand-text); }

.site-footer__base {
  display: flex;
  flex-wrap: wrap;
  gap: var(--s-3);
  justify-content: space-between;
  margin-top: var(--s-12);
  padding-top: var(--s-6);
  border-top: 1px solid var(--line);
  font-size: var(--t-xs);
  color: var(--ink-faint);
}

/* ----------------------------------------------------------- scroll reveal */

[data-reveal] {
  opacity: 0;
  transform: translateY(18px);
  transition: opacity 0.6s var(--ease), transform 0.6s var(--ease);
}
[data-reveal].is-visible { opacity: 1; transform: none; }

.is-filtered-out { display: none !important; }

/* ------------------------------------------------------- reduced motion */

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
  [data-reveal] { opacity: 1; transform: none; }
  .code-window--animated .code-window__panel.is-active .cw-line { opacity: 1; }
  .marquee__track { animation: none; }
}

/* --------------------------------------------------------------- printing */

@media print {
  .site-header, .site-footer, .tutorial__toc, .pager, .tutorial__end,
  .aurora, .grid-overlay, .reading-progress, .code-block__copy { display: none !important; }
  body { background: #fff; color: #000; }
  .prose { max-width: none; }
  .code-block { border: 1px solid #ccc; }
  .code-block pre { background: #f6f8fa; color: #111; }
}

/* ==========================================================================
   Search palette, progress tracking, quizzes
   ========================================================================== */

/* -------------------------------------------------------- search trigger */

.search-trigger {
  display: inline-flex;
  align-items: center;
  gap: var(--s-2);
  height: 38px;
  padding: 0 0.6rem 0 0.7rem;
  border: 1px solid var(--line);
  border-radius: 11px;
  background: var(--surface);
  color: var(--ink-muted);
  font-size: var(--t-sm);
  font-weight: 600;
  cursor: pointer;
  transition: all 0.2s var(--ease);
}
.search-trigger svg { width: 17px; height: 17px; }
.search-trigger:hover {
  color: var(--brand-text);
  border-color: var(--brand-300);
  background: var(--brand-50);
}
.search-trigger__kbd,
.palette__esc,
.palette__foot kbd {
  display: inline-flex;
  align-items: center;
  gap: 1px;
  padding: 0.1rem 0.35rem;
  border: 1px solid var(--line-strong);
  border-bottom-width: 2px;
  border-radius: 5px;
  background: var(--surface-2);
  font-family: var(--font);
  font-size: 0.68rem;
  font-weight: 700;
  color: var(--ink-faint);
  line-height: 1.5;
}

@media (max-width: 1080px) {
  .search-trigger__label, .search-trigger__kbd { display: none; }
  .search-trigger { width: 38px; padding: 0; justify-content: center; }
}

/* --------------------------------------------------------------- palette */

.palette {
  position: fixed;
  inset: 0;
  z-index: 200;
  display: grid;
  align-items: start;
  justify-items: center;
  padding: clamp(1rem, 9vh, 7rem) var(--s-4) var(--s-4);
}
body.palette-open { overflow: hidden; }

.palette__backdrop {
  position: absolute;
  inset: 0;
  background: rgb(8 17 31 / 0.5);
  backdrop-filter: blur(3px);
  -webkit-backdrop-filter: blur(3px);
  animation: fade-in 0.16s var(--ease);
}

.palette__panel {
  position: relative;
  width: min(100%, 40rem);
  max-height: min(32rem, 80vh);
  display: grid;
  grid-template-rows: auto minmax(0, 1fr) auto;
  overflow: hidden;
  background: var(--surface);
  border: 1px solid var(--line-strong);
  border-radius: var(--radius-lg);
  box-shadow: 0 24px 70px -20px rgb(8 17 31 / 0.45), 0 2px 8px rgb(8 17 31 / 0.12);
  animation: palette-in 0.18s var(--ease);
}

@keyframes fade-in { from { opacity: 0; } to { opacity: 1; } }
@keyframes palette-in {
  from { opacity: 0; transform: translateY(-8px) scale(0.985); }
  to { opacity: 1; transform: none; }
}

.palette__search {
  display: flex;
  align-items: center;
  gap: var(--s-3);
  padding: var(--s-4) var(--s-5);
  border-bottom: 1px solid var(--line);
}
.palette__search > svg { width: 19px; height: 19px; color: var(--ink-faint); flex: none; }
.palette__input {
  flex: 1;
  min-width: 0;
  border: none;
  outline: none;
  background: none;
  font-size: var(--t-lg);
  color: var(--ink);
}
.palette__input::placeholder { color: var(--ink-faint); }
.palette__input::-webkit-search-cancel-button { display: none; }

.palette__results { overflow-y: auto; padding: var(--s-2); }

.palette__empty {
  padding: var(--s-8) var(--s-5);
  text-align: center;
  color: var(--ink-muted);
  font-size: var(--t-sm);
  line-height: 1.6;
}
.palette__empty em {
  font-style: normal;
  font-weight: 650;
  color: var(--brand-text);
}

.palette__item {
  display: flex;
  align-items: center;
  gap: var(--s-3);
  padding: var(--s-3) var(--s-4);
  border-radius: var(--radius-sm);
  color: var(--ink);
  transition: background 0.12s var(--ease);
}
.palette__item:hover { color: var(--ink); background: var(--surface-3); }
.palette__item.is-active { color: var(--ink); background: var(--brand-100); }

.palette__kind {
  flex: none;
  width: 4.5rem;
  padding: 0.16rem 0;
  border-radius: 999px;
  text-align: center;
  font-size: 0.66rem;
  font-weight: 750;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  border: 1px solid var(--line-strong);
  color: var(--ink-muted);
}
.palette__kind--tutorial { color: var(--brand-text); border-color: var(--brand-200); background: var(--brand-50); }
.palette__kind--video { color: #c62a2f; border-color: #f3c7c8; background: #fff5f5; }
.palette__kind--track { color: #0f7a5f; border-color: #b6e2d4; background: #f0fbf7; }
:root[data-theme='dark'] .palette__kind--video { color: #ff9ea0; border-color: #4a2226; background: #2a1416; }
:root[data-theme='dark'] .palette__kind--track { color: #7fdcbc; border-color: #1c4438; background: #10241d; }

.palette__text { display: grid; grid-template-columns: minmax(0, 1fr); gap: 1px; min-width: 0; }
.palette__title {
  font-weight: 640;
  font-size: var(--t-sm);
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}
.palette__sub {
  font-size: var(--t-xs);
  color: var(--ink-muted);
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}
.palette__mins {
  flex: none;
  font-size: var(--t-xs);
  font-weight: 620;
  color: var(--ink-faint);
  font-variant-numeric: tabular-nums;
}

.palette__foot {
  display: flex;
  align-items: center;
  gap: var(--s-4);
  padding: var(--s-3) var(--s-5);
  border-top: 1px solid var(--line);
  background: var(--surface-2);
  font-size: var(--t-xs);
  color: var(--ink-faint);
}
.palette__foot span { display: inline-flex; align-items: center; gap: 5px; }
.palette__foot-spacer { margin-left: auto; }

@media (max-width: 620px) {
  .palette__foot span:not([data-palette-count]):not(.palette__foot-spacer) { display: none; }
}

/* -------------------------------------------------------- progress ring */

.ring {
  position: relative;
  display: inline-grid;
  place-items: center;
  flex: none;
}
.ring svg { transform: rotate(-90deg); overflow: visible; }
.ring circle { fill: none; stroke-width: 3.2; }
.ring__track { stroke: var(--line); }
.ring__value {
  stroke: var(--track-color, var(--brand-500));
  stroke-linecap: round;
  stroke-dasharray: 97.4;
  stroke-dashoffset: calc(97.4 - 97.4 * var(--value, 0));
  transition: stroke-dashoffset 0.6s var(--ease);
}
.ring.is-complete .ring__value { stroke: #0f9d76; }
.ring__label {
  position: absolute;
  font-size: 0.64rem;
  font-weight: 750;
  color: var(--ink-muted);
  font-variant-numeric: tabular-nums;
}
.ring.is-complete .ring__label { color: #0f9d76; }

.track-section__head .ring { margin-left: auto; align-self: center; }

/* ------------------------------------------------------------- resume */

.resume-wrap { padding-bottom: var(--s-8); }

.resume {
  display: flex;
  align-items: center;
  gap: var(--s-5);
  padding: var(--s-5) var(--s-6);
  border: 1px solid var(--brand-200);
  border-radius: var(--radius-lg);
  background: linear-gradient(120deg, var(--brand-50), var(--surface) 60%);
  color: var(--ink);
  box-shadow: var(--shadow-sm);
  transition: all 0.22s var(--ease);
}
.resume:hover {
  color: var(--ink);
  transform: translateY(-2px);
  border-color: var(--brand-300);
  box-shadow: var(--shadow);
}
.resume__body { display: grid; grid-template-columns: minmax(0, 1fr); gap: 2px; min-width: 0; }
.resume__eyebrow {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  font-size: var(--t-xs);
  font-weight: 720;
  letter-spacing: 0.07em;
  text-transform: uppercase;
  color: var(--brand-text);
}
.resume__eyebrow svg { width: 14px; height: 14px; }
.resume__title {
  font-size: var(--t-lg);
  font-weight: 700;
  letter-spacing: -0.02em;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}
.resume__meta { font-size: var(--t-sm); color: var(--ink-muted); }
.resume__go {
  margin-left: auto;
  display: grid;
  place-items: center;
  width: 40px;
  height: 40px;
  flex: none;
  border-radius: 50%;
  background: var(--brand-500);
  color: #fff;
  box-shadow: var(--shadow-brand);
  transition: transform 0.22s var(--ease);
}
.resume__go svg { width: 19px; height: 19px; }
.resume:hover .resume__go { transform: translateX(3px); }

@media (max-width: 620px) {
  .resume { flex-wrap: wrap; gap: var(--s-4); }
  .resume__go { margin-left: 0; }
}

/* --------------------------------------------------- completion markers */

.tutorial-card { position: relative; }
.tutorial-card__done {
  position: absolute;
  top: var(--s-4);
  right: var(--s-4);
  z-index: 1;
  display: inline-flex;
  align-items: center;
  gap: 4px;
  padding: 0.15rem 0.5rem;
  border-radius: 999px;
  background: #0f9d76;
  color: #fff;
  font-size: 0.66rem;
  font-weight: 750;
  letter-spacing: 0.04em;
  text-transform: uppercase;
}
.tutorial-card__done svg { width: 12px; height: 12px; }
.tutorial-card.is-done .tutorial-card__link { opacity: 0.82; }
.tutorial-card.is-done:hover .tutorial-card__link { opacity: 1; }

.syllabus__tick {
  display: grid;
  place-items: center;
  width: 22px;
  height: 22px;
  border-radius: 50%;
  background: #0f9d76;
  color: #fff;
}
.syllabus__tick svg { width: 13px; height: 13px; }
.syllabus__row.is-done .syllabus__title { color: var(--ink-muted); }

.button.is-done { color: #0f9d76; border-color: #9fdcc8; background: #f0fbf7; }
:root[data-theme='dark'] .button.is-done { color: #7fdcbc; border-color: #1c4438; background: #10241d; }
.button.is-done:hover { color: #0f9d76; }
:root[data-theme='dark'] .button.is-done:hover { color: #7fdcbc; }

.toc__progress {
  display: flex;
  align-items: center;
  gap: var(--s-3);
  margin-top: var(--s-3);
  padding: var(--s-3) var(--s-4);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--surface);
}
.toc__progress strong { display: block; font-size: var(--t-sm); }
.toc__progress em { font-style: normal; font-size: var(--t-xs); color: var(--ink-muted); }

/* ---------------------------------------------------------------- quiz */

.quiz {
  margin-top: var(--s-12);
  padding: var(--s-6);
  border: 1px solid var(--brand-200);
  border-radius: var(--radius-lg);
  background: linear-gradient(150deg, var(--brand-50), var(--surface) 70%);
}
.quiz__head { display: flex; align-items: flex-start; gap: var(--s-3); margin-bottom: var(--s-5); }
.quiz__head > svg { width: 22px; height: 22px; color: var(--brand-text); flex: none; margin-top: 3px; }
.quiz__title { font-size: var(--t-xl); margin: 0; color: var(--ink); }
.quiz__lead { font-size: var(--t-sm); color: var(--ink-muted); margin-top: 2px; line-height: 1.55; }
.quiz__score {
  margin-left: auto;
  flex: none;
  padding: 0.3rem 0.7rem;
  border-radius: 999px;
  border: 1px solid var(--line-strong);
  background: var(--surface);
  font-size: var(--t-sm);
  font-weight: 750;
  font-variant-numeric: tabular-nums;
  color: var(--ink-muted);
}
.quiz__score.is-perfect { color: #0f9d76; border-color: #9fdcc8; background: #f0fbf7; }

.quiz__list { display: grid; grid-template-columns: minmax(0, 1fr); gap: var(--s-6); }

/* `.prose ol li` matches by descendant, so the option lists inherit decimal
   markers from the question list. Out-specify it rather than reaching for
   !important. */
.prose .quiz li, .quiz li { list-style: none; }
.prose .quiz__title { margin: 0; padding: 0; }

.quiz__question { display: grid; grid-template-columns: minmax(0, 1fr); gap: var(--s-3); }

.quiz__prompt {
  display: flex;
  gap: var(--s-3);
  font-weight: 650;
  color: var(--ink);
  font-size: var(--t-md);
  line-height: 1.5;
}
.quiz__prompt-text { min-width: 0; }
.quiz__n {
  flex: none;
  display: grid;
  place-items: center;
  width: 24px;
  height: 24px;
  margin-top: 1px;
  border-radius: 50%;
  /* brand-500 only reaches 3.7:1 against white; small text needs 4.5. */
  background: var(--brand-600);
  color: #fff;
  font-size: var(--t-xs);
  font-weight: 750;
}

.quiz__options { display: grid; grid-template-columns: minmax(0, 1fr); gap: var(--s-2); padding-left: calc(24px + var(--s-3)); }
.quiz__options li { list-style: none; }

.quiz__option {
  width: 100%;
  display: flex;
  align-items: flex-start;
  gap: var(--s-3);
  padding: var(--s-3) var(--s-4);
  border: 1.5px solid var(--line);
  border-radius: var(--radius-sm);
  background: var(--surface);
  color: var(--ink-2);
  text-align: left;
  font-size: var(--t-sm);
  line-height: 1.5;
  cursor: pointer;
  transition: all 0.16s var(--ease);
}
.quiz__option:hover:not(:disabled) {
  border-color: var(--brand-300);
  background: var(--brand-50);
  transform: translateX(2px);
}
.quiz__option:disabled { cursor: default; }

.quiz__marker {
  flex: none;
  display: grid;
  place-items: center;
  width: 20px;
  height: 20px;
  border-radius: 6px;
  border: 1.5px solid var(--line-strong);
  font-size: 0.68rem;
  font-weight: 750;
  color: var(--ink-faint);
}

.quiz__option.is-correct,
.quiz__option.is-answer {
  border-color: #0f9d76;
  background: #f0fbf7;
  color: #0b6b52;
}
.quiz__option.is-correct .quiz__marker,
.quiz__option.is-answer .quiz__marker {
  border-color: #0f9d76;
  background: #0f9d76;
  color: #fff;
}
.quiz__option.is-wrong {
  border-color: #e0484d;
  background: #fff5f5;
  color: #a8262b;
}
.quiz__option.is-wrong .quiz__marker { border-color: #e0484d; background: #e0484d; color: #fff; }

:root[data-theme='dark'] .quiz__option.is-correct,
:root[data-theme='dark'] .quiz__option.is-answer { background: #10241d; color: #7fdcbc; }
:root[data-theme='dark'] .quiz__option.is-wrong { background: #2a1416; color: #ff9ea0; }
:root[data-theme='dark'] .quiz__score.is-perfect { background: #10241d; color: #7fdcbc; border-color: #1c4438; }

.quiz__answer {
  margin-left: calc(24px + var(--s-3));
  font-size: var(--t-sm);
  color: var(--ink-muted);
}
.quiz__answer summary {
  cursor: pointer;
  font-weight: 640;
  color: var(--brand-text);
  list-style: none;
  padding: var(--s-1) 0;
}
.quiz__answer summary::-webkit-details-marker { display: none; }
.quiz__answer summary::before { content: '▸ '; }
.quiz__answer[open] summary::before { content: '▾ '; }
.quiz__answer[open] summary { margin-bottom: var(--s-2); }
.quiz__answer p { line-height: 1.6; }
.quiz__answer p + p { margin-top: var(--s-2); }
.quiz__question.is-answered .quiz__answer summary { color: var(--ink-faint); }

/* ------------------------------------------------------------ back to top */

.to-top {
  position: fixed;
  right: var(--s-6);
  bottom: var(--s-6);
  z-index: 90;
  display: grid;
  place-items: center;
  width: 42px;
  height: 42px;
  border: 1px solid var(--line);
  border-radius: 50%;
  background: var(--surface);
  color: var(--ink-2);
  cursor: pointer;
  box-shadow: var(--shadow);
  opacity: 0;
  visibility: hidden;
  transform: translateY(8px);
  transition: all 0.24s var(--ease);
}
.to-top svg { width: 19px; height: 19px; transform: rotate(180deg); }
.to-top:hover { color: var(--brand-text); border-color: var(--brand-300); background: var(--brand-50); }
body.is-scrolled .to-top { opacity: 1; visibility: visible; transform: none; }

@media (max-width: 620px) { .to-top { right: var(--s-4); bottom: var(--s-4); } }

@media print {
  .palette, .to-top, .quiz, .resume-wrap { display: none !important; }
}

/* ==========================================================================
   Articles — short-form answers
   ========================================================================== */

.answer-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(min(100%, 300px), 1fr));
  gap: var(--s-4);
  padding-bottom: var(--s-24);
}

.answer-card {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  box-shadow: var(--shadow-sm);
  transition: transform 0.22s var(--ease), box-shadow 0.22s var(--ease),
              border-color 0.22s var(--ease);
}
.answer-card:hover {
  transform: translateY(-3px);
  border-color: color-mix(in srgb, var(--track-color) 45%, transparent);
  box-shadow: 0 2px 6px rgb(12 28 48 / 0.06),
              0 18px 36px -18px color-mix(in srgb, var(--track-color) 60%, transparent);
}

.answer-card__link {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: var(--s-2);
  align-content: start;
  height: 100%;
  padding: var(--s-5);
  color: var(--ink);
}
.answer-card__link:hover { color: var(--ink); }

.answer-card__track {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  font-size: var(--t-xs);
  font-weight: 700;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  color: var(--track-text);
}
.answer-card__track svg { width: 15px; height: 15px; }

.answer-card__title { font-size: var(--t-md); line-height: 1.34; }
.answer-card__summary {
  font-size: var(--t-sm);
  color: var(--ink-muted);
  line-height: 1.55;
}
.answer-card__foot {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-top: auto;
  padding-top: var(--s-3);
  border-top: 1px solid var(--line);
  font-size: var(--t-xs);
  font-weight: 640;
  color: var(--ink-faint);
}
.answer-card__foot > span { display: inline-flex; align-items: center; gap: 5px; }
.answer-card__foot svg { width: 13px; height: 13px; }
.answer-card__go { color: var(--track-text); }
.answer-card__go svg { transition: transform 0.22s var(--ease); }
.answer-card:hover .answer-card__go svg { transform: translateX(3px); }

/* ------------------------------------------------------- article page */

.answer__hero { position: relative; overflow: hidden; padding: var(--s-10) 0 var(--s-8); }
.answer__hero .shell {
  position: relative;
  z-index: 1;
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: var(--s-4);
}

.answer__title {
  font-size: clamp(1.85rem, 3.8vw, 2.7rem);
  max-width: 24ch;
  letter-spacing: -0.03em;
}

.answer__meta { display: flex; flex-wrap: wrap; gap: var(--s-2); }
.answer__badge {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 0.38rem 0.78rem;
  border-radius: 999px;
  border: 1px solid var(--line);
  background: var(--surface);
  font-size: var(--t-xs);
  font-weight: 650;
  color: var(--ink-2);
}
.answer__badge svg { width: 15px; height: 15px; }
.answer__badge--track {
  color: var(--track-text);
  border-color: color-mix(in srgb, var(--track-color) 35%, transparent);
}
.answer__badge--lesson { color: var(--brand-text); border-color: var(--brand-200); background: var(--brand-50); }
.answer__badge--lesson:hover { color: var(--brand-text-strong); border-color: var(--brand-300); }

.answer__layout {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: var(--s-10);
  padding-bottom: var(--s-24);
}
@media (min-width: 1040px) {
  .answer__layout { grid-template-columns: minmax(0, 1fr) 16rem; gap: var(--s-12); }
}

.answer__aside { display: none; }
@media (min-width: 1040px) {
  .answer__aside {
    display: grid;
    grid-template-columns: minmax(0, 1fr);
    gap: var(--s-5);
    align-content: start;
    position: sticky;
    top: calc(var(--header-h) + var(--s-6));
  }
}
.answer__aside .toc { position: static; }

.answer__cta {
  padding: var(--s-5);
  border-radius: var(--radius);
  border: 1px solid var(--line);
  background: var(--surface);
}
.answer__cta h2 { font-size: var(--t-md); margin-bottom: var(--s-1); }
.answer__cta p { font-size: var(--t-sm); color: var(--ink-muted); margin-bottom: var(--s-4); line-height: 1.5; }

/* The short answer, up top */
.answer__lead {
  padding: var(--s-5) var(--s-6);
  border-radius: var(--radius);
  border: 1px solid color-mix(in srgb, var(--track-color) 30%, transparent);
  border-left: 3px solid var(--track-color);
  background: color-mix(in srgb, var(--track-color) 7%, var(--surface));
}
.answer__lead-label {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  margin-bottom: var(--s-2);
  font-size: var(--t-xs);
  font-weight: 750;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--track-text);
}
.answer__lead-label svg { width: 14px; height: 14px; }
.answer__lead p { font-size: var(--t-lg); line-height: 1.6; color: var(--ink); }
.prose .answer__lead { margin-top: 0; }

.answer__lesson {
  display: flex;
  gap: var(--s-4);
  align-items: flex-start;
  margin-top: var(--s-12);
  padding: var(--s-6);
  border-radius: var(--radius-lg);
  border: 1px solid var(--brand-200);
  background: linear-gradient(140deg, var(--brand-50), var(--surface) 70%);
}
.answer__lesson > svg { width: 22px; height: 22px; color: var(--brand-text); flex: none; margin-top: 2px; }
.answer__lesson h2 { font-size: var(--t-lg); margin: 0 0 var(--s-2); }
.prose .answer__lesson h2 { margin-top: 0; padding-top: 0; }
.answer__lesson p { font-size: var(--t-sm); color: var(--ink-muted); margin-bottom: var(--s-4); }

/* ------------------------------------------------------------- related */

.related { margin-top: var(--s-12); }
.related__heading {
  display: flex;
  align-items: center;
  gap: var(--s-2);
  font-size: var(--t-xs) !important;
  font-weight: 720;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--ink-faint);
  margin-bottom: var(--s-4) !important;
}
.prose .related__heading { margin-top: 0; padding-top: 0; }
.related__heading svg { width: 15px; height: 15px; }

.related__list {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: var(--s-2);
  padding-left: 0 !important;
}
.related__list li { list-style: none !important; }
.related__list a {
  display: flex;
  align-items: center;
  gap: var(--s-4);
  padding: var(--s-3) var(--s-4);
  border: 1px solid var(--line);
  border-radius: var(--radius-sm);
  background: var(--surface);
  color: var(--ink);
  text-decoration: none;
  transition: all 0.18s var(--ease);
}
.related__list a:hover {
  color: var(--ink);
  transform: translateX(3px);
  border-color: var(--brand-300);
  background: var(--brand-50);
}
.related__title { flex: 1; min-width: 0; font-size: var(--t-sm); font-weight: 620; }
.related__meta {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  flex: none;
  font-size: var(--t-xs);
  color: var(--ink-faint);
}
.related__meta svg { width: 12px; height: 12px; }

@media (min-width: 40rem) {
  .related__list { grid-template-columns: repeat(2, minmax(0, 1fr)); }
}

/* ------------------------------------------------ track page additions */

.track-section__sub--spaced { margin-top: var(--s-6); }

.answer-list {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 1px;
}
.answer-list li { list-style: none; }
.answer-list a {
  display: block;
  padding: var(--s-2) var(--s-3);
  border-radius: var(--radius-sm);
  font-size: var(--t-sm);
  line-height: 1.45;
  color: var(--ink-2);
  transition: all 0.16s var(--ease);
}
.answer-list a:hover { color: var(--track-text); background: var(--surface-3); }

.track-section__more {
  display: inline-flex;
  align-items: center;
  gap: 5px;
  margin-top: var(--s-3);
  padding: var(--s-2) var(--s-3);
  font-size: var(--t-xs);
  font-weight: 680;
  color: var(--track-text);
}
.track-section__more svg { width: 14px; height: 14px; transition: transform 0.2s var(--ease); }
.track-section__more:hover svg { transform: translateX(3px); }

/* --------------------------------------------------- palette additions */

.palette__kind--article {
  color: #7440e0;
  border-color: #d8c9f7;
  background: #f7f3ff;
}
:root[data-theme='dark'] .palette__kind--article {
  color: #c9b4ff;
  border-color: #2f2350;
  background: #1a1430;
}

@media print {
  .answer__aside, .related, .answer__lesson { display: none !important; }
}

/* 107 cards on one page: skip layout and paint for off-screen ones. The
   contain-intrinsic-size keeps the scrollbar honest while they are skipped. */
.answer-grid > .answer-card {
  content-visibility: auto;
  contain-intrinsic-size: auto 190px;
}
.answer-grid--home { padding-bottom: 0; }
.answer-grid--home > .answer-card { content-visibility: visible; }