/* ==========================================================================
   VuHM — Problem-first
   Every case opens with the problem, in one large sentence; the work proves it.
   Pure CSS. Order: tokens, base, header, hero, case sheets, principles, contact,
   footer, loader, motion (time-based, then scroll-linked with static fallbacks),
   desktop stacking, Vietnamese, responsive, reduced motion.
   ========================================================================== */

@property --pct { syntax: "<integer>"; inherits: true; initial-value: 0; }

/* ---------- Tokens ---------- */
:root {
  /* ground and surfaces */
  --ink: #0d0e10;
  --surface-1: #131417;
  --surface-2: #181a1e;
  --line: rgba(243, 241, 234, .14);
  --line-strong: rgba(243, 241, 234, .3);
  /* text */
  --text: #f3f1ea;
  --text-2: #a9a79e;            /* secondary text; 7.9:1 on --ink */
  /* the single accent: a highlighter that marks the words carrying the problem */
  --mark: #ffd43b;
  --mark-ink: #16140a;
  /* type */
  --font-display: "Bricolage Grotesque", "Be Vietnam Pro", system-ui, sans-serif;
  --font-text: "Be Vietnam Pro", system-ui, -apple-system, "Segoe UI", sans-serif;
  --fs-display: clamp(2.75rem, 6.6vw, 5.75rem);
  --fs-problem: clamp(1.875rem, min(3.7vw, 6.5vh), 3.5rem);
  --fs-h2: clamp(2rem, 4.2vw, 3.5rem);
  --fs-lead: clamp(1.125rem, 1.6vw, 1.3125rem);
  --fs-body: 1.0625rem;
  --fs-small: .9375rem;
  --fs-label: .875rem;
  /* space (8px base) */
  --s-1: .5rem; --s-2: 1rem; --s-3: 1.5rem; --s-4: 2rem; --s-5: 3rem; --s-6: 5rem; --s-7: 8rem;
  --gutter: clamp(1.25rem, 4vw, 3rem);
  --maxw: 96rem;
  --radius: 1.75rem;
  --radius-m: 1.25rem;
  /* motion */
  --ease-out: cubic-bezier(.16, 1, .3, 1);
  --ease-io: cubic-bezier(.76, 0, .24, 1);
  --hero-delay: .15s;           /* pages without a loader */
  --shadow-sheet: 0 -1.5rem 3rem rgba(0, 0, 0, .5);
}

/* ---------- Base ---------- */
*, *::before, *::after { box-sizing: border-box; }
html {
  color-scheme: dark;
  background: var(--ink);
  scroll-behavior: smooth;
  scrollbar-color: #3b3d42 var(--ink);
  -webkit-text-size-adjust: 100%;
}
body {
  margin: 0;
  background: var(--ink);
  color: var(--text);
  font: 400 var(--fs-body)/1.65 var(--font-text);
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
  overflow-x: clip;
}
::selection { background: var(--mark); color: var(--mark-ink); }
img, video { display: block; max-width: 100%; height: auto; }
a { color: inherit; text-decoration-color: var(--mark); text-underline-offset: .28em; text-decoration-thickness: .08em; }
h1, h2, h3, p, ul, ol, dl, dd, figure { margin: 0; }
ul, ol { padding: 0; list-style: none; }
:focus-visible { outline: 3px solid var(--mark); outline-offset: 4px; border-radius: 4px; }
.icon { flex: none; }
.sr { position: absolute; width: 1px; height: 1px; margin: -1px; padding: 0; overflow: hidden; clip-path: inset(50%); white-space: nowrap; border: 0; }

.skip {
  position: fixed; left: var(--s-2); top: -4rem; z-index: 200;
  background: var(--mark); color: var(--mark-ink); padding: var(--s-1) var(--s-2);
  font-weight: 700; text-decoration: none; border-radius: .5rem;
}
.skip:focus { top: var(--s-1); }

/* The highlighter: marks the words that carry the problem */
mark {
  color: var(--mark-ink);
  background: linear-gradient(var(--mark), var(--mark)) 0 50% / 100% 100% no-repeat;
  padding: 0 .16em; margin: 0;
  border-radius: .14em;
  -webkit-box-decoration-break: clone; box-decoration-break: clone;
}

/* Word masks (generated by <split>): the line rises out of a clip */
.w { display: inline-block; overflow: hidden; vertical-align: top; padding-block: .14em; margin-block: -.14em; }
.w > span { display: inline-block; }

/* ---------- Header ---------- */
.top {
  position: fixed; inset: 0 0 auto 0; z-index: 50;
  display: flex; align-items: center; justify-content: space-between; gap: var(--s-2);
  padding: 1rem var(--gutter);
  background: rgba(13, 14, 16, .98); border-bottom: 1px solid var(--line);
  color: var(--text);
}
.top__logo { font: 700 1.25rem/1 var(--font-display); letter-spacing: -.02em; text-decoration: none; }
.top__nav { display: flex; align-items: center; gap: clamp(1rem, 3vw, 2.25rem); font-size: var(--fs-small); font-weight: 500; }
.top__nav a { position: relative; text-decoration: none; padding-block: .25rem; }
.top__nav > a::after {
  content: ""; position: absolute; left: 0; right: 0; bottom: -.1rem; height: 2px; background: currentColor;
  transform: scaleX(0); transform-origin: left; transition: transform .45s var(--ease-out);
}
.top__nav > a:hover::after { transform: scaleX(1); }
.lang { display: inline-flex; align-items: baseline; gap: .6rem; font-weight: 500; padding-block: .25rem; }
.lang__on { font-weight: 700; text-decoration: underline; text-decoration-thickness: 2px; text-underline-offset: .3em; }
.lang a { opacity: .65; }
.lang a:hover { opacity: 1; }

/* ---------- Hero ---------- */
.hero {
  min-height: 100svh;
  display: grid; grid-template-rows: 1fr auto;
  max-width: var(--maxw); margin-inline: auto;
  padding: clamp(6rem, 14vh, 9rem) var(--gutter) var(--s-4);
}
.hero__main { align-self: center; padding-block: var(--s-4); }
.hero__title {
  font: 650 var(--fs-display)/1.04 var(--font-display); font-stretch: 92%;
  letter-spacing: -.012em; text-wrap: balance; max-width: 19ch;
}
.hero__sub { margin-top: var(--s-4); max-width: 46ch; color: var(--text-2); font-size: var(--fs-lead); }

.index { border-bottom: 1px solid var(--line); margin-inline: -1rem; }
.index a {
  position: relative; isolation: isolate;
  display: grid; grid-template-columns: minmax(9rem, 18rem) minmax(0, 1fr) 11rem 1.25rem; align-items: baseline; column-gap: var(--s-3);
  padding: 1.1rem 1rem;
  border-top: 1px solid var(--line);
  text-decoration: none;
  transition: color .3s var(--ease-out);
}
.index a::before {
  content: ""; position: absolute; inset: 0; z-index: -1; background: var(--mark);
  transform: scaleY(0); transform-origin: bottom; transition: transform .5s var(--ease-out);
}
.index a:hover, .index a:focus-visible { color: var(--mark-ink); }
.index a:hover::before, .index a:focus-visible::before { transform: scaleY(1); }
.index a:focus-visible { outline: 2px solid var(--mark-ink); outline-offset: -8px; }
.index__name { font: 650 clamp(1.375rem, 2.4vw, 1.875rem)/1.2 var(--font-display); letter-spacing: -.01em; transition: translate .5s var(--ease-out); }
.index__problem { color: var(--text-2); transition: color .3s var(--ease-out); }
.index__meta { color: var(--text-2); font-size: var(--fs-small); white-space: nowrap; text-align: right; transition: color .3s var(--ease-out); }
.index a:hover .index__name, .index a:focus-visible .index__name { translate: .5rem 0; }
.index a:hover .index__problem, .index a:hover .index__meta,
.index a:focus-visible .index__problem, .index a:focus-visible .index__meta { color: var(--mark-ink); }
.index .icon { transition: translate .5s var(--ease-out); }
.index a:hover .icon, .index a:focus-visible .icon { translate: .35rem 0; }

/* ---------- Case sheets ---------- */
.cases { position: relative; }
.case {
  position: relative;
  background: var(--surface-1);
  border-top: 1px solid var(--line);
  border-radius: var(--radius) var(--radius) 0 0;
  box-shadow: var(--shadow-sheet);
}
.case:nth-child(even) { background: var(--surface-2); }
.case__inner {
  max-width: var(--maxw); margin-inline: auto;
  padding: clamp(5.5rem, 10vh, 7rem) var(--gutter) clamp(2rem, 5vh, 3.5rem);
  display: grid; gap: var(--s-4);
  grid-template-columns: repeat(12, minmax(0, 1fr));
}
.case__head { grid-column: 1 / 4; align-self: start; }
.case__name { font: 650 clamp(1.5rem, 2.2vw, 2rem)/1.15 var(--font-display); letter-spacing: -.02em; }
.case__meta { margin-top: var(--s-1); color: var(--text-2); font-size: var(--fs-small); }
.case__problem {
  grid-column: 4 / 13;
  font: 600 var(--fs-problem)/1.12 var(--font-display); font-stretch: 90%;
  letter-spacing: -.01em; text-wrap: balance;
}
.case__visual {
  grid-column: 1 / 9; position: relative; overflow: hidden; min-height: 0;
  aspect-ratio: 16 / 10;
  border-radius: var(--radius-m); background: var(--bg, #08090a);
}
.case__visual img { position: absolute; inset: 0; width: 100%; height: 100%; object-fit: var(--fit, cover); object-position: var(--pos, 50% 50%); }
.case__side { grid-column: 9 / 13; display: flex; flex-direction: column; justify-content: space-between; gap: var(--s-3); min-height: 0; }
.case__facts { display: grid; gap: var(--s-3); }
.case__facts dt { font-size: var(--fs-label); font-weight: 700; letter-spacing: .08em; text-transform: uppercase; color: var(--text-2); }
.case__facts dd { margin-top: .35rem; font-size: 1rem; line-height: 1.55; }
.case__sure { padding: var(--s-2) var(--s-3); border: 1px solid var(--line-strong); border-radius: var(--radius-m); }
.case__foot { display: grid; gap: var(--s-2); }
.case__role { font-size: 1rem; color: var(--text-2); }

.cta {
  display: inline-flex; align-items: center; gap: .75rem; width: fit-content;
  padding: .85rem 1.4rem; border-radius: 999px;
  background: var(--text); color: var(--ink);
  font-weight: 700; text-decoration: none;
  transition: background .35s var(--ease-out), translate .35s var(--ease-out);
}
.cta:hover { background: var(--mark); translate: 0 -2px; }
.cta .icon { transition: translate .35s var(--ease-out); }
.cta:hover .icon { translate: .3rem 0; }

/* ---------- Principles ---------- */
.principles { max-width: var(--maxw); margin-inline: auto; padding: var(--s-7) var(--gutter) var(--s-6); background: var(--ink); position: relative; }
.principles__title { font: 650 var(--fs-h2)/1.08 var(--font-display); font-stretch: 92%; letter-spacing: -.01em; text-wrap: balance; }
.principles__list { margin-top: var(--s-5); border-bottom: 1px solid var(--line); }
.principles__list li {
  display: grid; grid-template-columns: minmax(0, 1.3fr) minmax(0, 1fr); gap: var(--s-2) var(--s-5);
  padding: var(--s-4) 0; border-top: 1px solid var(--line); align-items: baseline;
}
.principles__list h3 { font: 600 clamp(1.5rem, 3vw, 2.5rem)/1.15 var(--font-display); font-stretch: 92%; letter-spacing: -.01em; }
.principles__list p { color: var(--text-2); font-size: var(--fs-lead); max-width: 40ch; }

/* ---------- Contact ---------- */
.contact { max-width: var(--maxw); margin-inline: auto; padding: var(--s-6) var(--gutter) var(--s-7); position: relative; background: var(--ink); }
.contact__title { font: 700 var(--fs-display)/1.04 var(--font-display); font-stretch: 90%; letter-spacing: -.012em; text-wrap: balance; }
.contact__lead { margin-top: var(--s-3); font-size: var(--fs-lead); color: var(--text-2); max-width: 44ch; }
.contact__mail {
  position: relative; isolation: isolate; display: inline-block; margin-top: var(--s-5);
  font: 650 clamp(1.75rem, 5.2vw, 4rem)/1.1 var(--font-display); font-stretch: 92%; letter-spacing: -.01em;
  text-decoration: none; word-break: break-word;
  transition: color .3s var(--ease-out);
}
.contact__mail::before { /* the underline that floods into a highlighter on hover */
  content: ""; position: absolute; inset: auto 0 0 0; z-index: -1; height: .09em; background: var(--mark);
  transition: height .5s var(--ease-out);
}
.contact__mail:hover { color: var(--mark-ink); }
.contact__mail:hover::before { height: 100%; }
.contact__grid { margin-top: var(--s-5); display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: var(--s-4) var(--s-5); border-top: 1px solid var(--line); padding-top: var(--s-4); }
.contact__grid dt { font-size: var(--fs-label); font-weight: 700; letter-spacing: .08em; text-transform: uppercase; color: var(--text-2); }
.contact__grid dd { margin-top: .4rem; font-size: var(--fs-lead); }
.contact__grid a { text-decoration-color: var(--line-strong); }
.contact__grid a:hover { text-decoration-color: var(--mark); }
.contact__links { display: flex; flex-wrap: wrap; gap: .4rem 1.5rem; }

.foot {
  max-width: var(--maxw); margin-inline: auto; padding: var(--s-3) var(--gutter) var(--s-4);
  display: flex; justify-content: space-between; gap: var(--s-2); flex-wrap: wrap;
  border-top: 1px solid var(--line); color: var(--text-2); font-size: var(--fs-small); background: var(--ink); position: relative;
}

/* ---------- Loader (CSS only, plays once per load) ---------- */
.loader { display: none; }
@media (prefers-reduced-motion: no-preference) {
  .home { --hero-delay: 2.6s; }
  .loader {
    --count: 1.6s; --split-at: 2.4s;
    display: block; position: fixed; inset: 0; z-index: 100; pointer-events: none;
    animation: loader-off 0s linear 3.35s both;
  }
  .loader__half { position: absolute; left: 0; right: 0; height: 50.2%; background: var(--ink); }
  .loader__half--top { top: 0; animation: curtain-up .9s var(--ease-io) var(--split-at) both; }
  .loader__half--bottom { bottom: 0; animation: curtain-down .9s var(--ease-io) var(--split-at) both; }
  .loader__ui {
    position: absolute; inset: 0; display: grid; grid-template-rows: auto 1fr auto; padding: var(--gutter);
    animation: ui-out .35s ease 2.3s both;
  }
  .loader__row { display: flex; justify-content: space-between; gap: var(--s-2); font-size: var(--fs-label); font-weight: 500; letter-spacing: .06em; text-transform: uppercase; color: var(--text-2); }
  .loader__word {
    place-self: center; display: flex; overflow: hidden;
    font: 800 clamp(5rem, 42vw, 30rem)/.9 var(--font-display); font-stretch: 80%; letter-spacing: -.01em; padding-inline: .02em; position: relative;
  }
  .loader__word::before { /* the highlighter marks the name before the curtains part */
    content: ""; position: absolute; left: 0; right: 0; top: 4%; bottom: 6%; background: var(--mark);
    transform: scaleX(0); transform-origin: left; animation: sweep .55s var(--ease-io) 1.75s both;
  }
  .loader__word span {
    position: relative; z-index: 1; display: block;
    color: transparent; -webkit-text-stroke: 1.5px rgba(243, 241, 234, .5);
    transform: translateY(105%); animation: rise .9s var(--ease-out) calc(.05s + var(--i) * .09s) both;
  }
  .loader__word span::after {
    content: attr(data-l); position: absolute; inset: 0;
    color: var(--text); -webkit-text-stroke: 1.5px var(--text);
    clip-path: inset(100% 0 0 0);
    animation: fill var(--count) var(--ease-io) .2s both, ink .25s ease calc(1.72s + var(--i) * .13s) both;
  }
  .loader__foot { display: grid; grid-template-columns: 1fr auto; align-items: end; gap: var(--s-2) var(--s-3); }
  .loader__bar { grid-column: 1 / -1; height: 2px; background: var(--line); position: relative; overflow: hidden; }
  .loader__bar::after { content: ""; position: absolute; inset: 0; background: var(--mark); transform: scaleX(0); transform-origin: left; animation: bar var(--count) var(--ease-io) .2s both; }
  .loader__status { position: relative; height: 1.6em; overflow: hidden; font-size: var(--fs-small); color: var(--text); }
  .loader__status span { position: absolute; left: 0; top: 0; white-space: nowrap; transform: translateY(110%); }
  .loader__status span:nth-child(1) { animation: status-1 var(--count) linear .2s both; }
  .loader__status span:nth-child(2) { animation: status-2 var(--count) linear .2s both; }
  .loader__status span:nth-child(3) { animation: status-3 var(--count) linear .2s both; }
  .loader__count { font: 700 clamp(2.5rem, 7vw, 5rem)/1 var(--font-display); font-stretch: 85%; font-variant-numeric: tabular-nums; animation: count var(--count) var(--ease-io) .2s both; }
  .loader__count::after { counter-reset: pct var(--pct); content: counter(pct, decimal-leading-zero) "%"; }
}
@keyframes loader-off { to { visibility: hidden; pointer-events: none; } }
@keyframes curtain-up { to { transform: translateY(-101%); } }
@keyframes curtain-down { to { transform: translateY(101%); } }
@keyframes ui-out { to { opacity: 0; transform: translateY(-.75rem); } }
@keyframes fill { to { clip-path: inset(0 0 0 0); } }
@keyframes sweep { to { transform: scaleX(1); } }
@keyframes ink { to { color: var(--mark-ink); -webkit-text-stroke-color: var(--mark-ink); } }
@keyframes bar { to { transform: scaleX(1); } }
@keyframes count { from { --pct: 0; } to { --pct: 100; } }
@keyframes status-1 { 0% { transform: translateY(110%); } 6%, 28% { transform: none; } 36%, 100% { transform: translateY(-110%); } }
@keyframes status-2 { 0%, 30% { transform: translateY(110%); } 38%, 62% { transform: none; } 70%, 100% { transform: translateY(-110%); } }
@keyframes status-3 { 0%, 64% { transform: translateY(110%); } 72%, 100% { transform: none; } }

/* ---------- Motion: time-based entrances (hero) ---------- */
@keyframes rise { from { transform: translateY(112%); } to { transform: none; } }
@keyframes fade-up { from { opacity: 0; transform: translateY(1.25rem); } to { opacity: 1; transform: none; } }
@keyframes mark-sweep { from { background-size: 0% 100%; color: var(--text); } to { background-size: 100% 100%; color: var(--mark-ink); } }
@keyframes unclip { from { clip-path: inset(10% 6% round var(--radius-m)); } to { clip-path: inset(0 round var(--radius-m)); } }
@keyframes drift { from { transform: scale(1.12); } to { transform: scale(1); } }
@keyframes lift { from { opacity: 0; transform: translateY(2rem); } to { opacity: 1; transform: none; } }

@media (prefers-reduced-motion: no-preference) {
  .hero__title .w > span { transform: translateY(112%); animation: rise 1s var(--ease-out) calc(var(--hero-delay) + var(--i) * 55ms) both; }
  .hero__title mark { animation: mark-sweep .9s var(--ease-io) calc(var(--hero-delay) + .75s) both; }
  .hero__sub { animation: fade-up .9s var(--ease-out) calc(var(--hero-delay) + .45s) both; }
  .index li { animation: fade-up .9s var(--ease-out) calc(var(--hero-delay) + .6s + var(--n, 0) * 90ms) both; }
  .index li:nth-child(1) { --n: 0; } .index li:nth-child(2) { --n: 1; } .index li:nth-child(3) { --n: 2; } .index li:nth-child(4) { --n: 3; }
}

/* ---------- Motion: scroll-linked (only where supported; static fallback otherwise) ---------- */
@media (prefers-reduced-motion: no-preference) {
  @supports (animation-timeline: view()) {
    .case mark { animation: mark-sweep linear both; animation-timeline: view(); animation-range: entry 35% entry 95%; }
    .case__visual { animation: unclip linear both; animation-timeline: view(); animation-range: entry 0% entry 70%; }
    .case__visual img { animation: drift linear both; animation-timeline: view(); animation-range: entry 0% entry 100%; }
    .case__head, .case__problem, .case__side { animation: lift linear both; animation-timeline: view(); animation-range: entry 8% entry 60%; }
    .principles__list li, .contact__grid > div { animation: lift linear both; animation-timeline: view(); animation-range: entry 5% entry 55%; }
    .contact__title { animation: lift linear both; animation-timeline: view(); animation-range: entry 5% entry 60%; }
  }
}

/* cross-document page transitions where supported */
@view-transition { navigation: auto; }

/* ---------- Desktop: case sheets stack as you scroll ---------- */
@media (min-width: 72rem) and (min-height: 50rem) {
  .case { position: sticky; top: 0; height: 100svh; overflow: hidden; }
  .case:not(:last-child) { margin-bottom: 60svh; }   /* dwell: each sheet stays pinned while it is read */
  .case__inner { height: 100%; grid-template-rows: auto minmax(0, 1fr); padding-bottom: clamp(1.5rem, 4vh, 3rem); }
  .case__visual { aspect-ratio: auto; height: 100%; }
}

/* ---------- Vietnamese: marks stack above capitals, give lines room ---------- */
:lang(vi) .hero__title, :lang(vi) .case__problem, :lang(vi) .contact__title, :lang(vi) .principles__title { line-height: 1.16; }
:lang(vi) .principles__list h3, :lang(vi) .case__name { line-height: 1.25; }

/* ---------- Responsive ---------- */
@media (max-width: 62rem) {
  .case { border-radius: var(--radius-m) var(--radius-m) 0 0; }
  .case__head, .case__problem, .case__visual, .case__side { grid-column: 1 / -1; }
  .case__head { display: flex; align-items: baseline; justify-content: space-between; gap: var(--s-2); flex-wrap: wrap; }
  .case__meta { margin-top: 0; }
  .case__side { gap: var(--s-4); }
  .index a { grid-template-columns: 1fr auto; row-gap: .15rem; }
  .index__problem { grid-column: 1 / -1; grid-row: 2; }
  .index__meta { display: none; }
  .principles__list li { grid-template-columns: 1fr; }
  .contact__grid { grid-template-columns: 1fr; }
}
@media (max-width: 40rem) {
  .top { padding-inline: 1rem; gap: .75rem; }
  .top__logo { font-size: 1.125rem; }
  .top__nav { gap: .85rem; font-size: .875rem; }
  .lang { gap: .4rem; }
  .top__nav > a:nth-child(2) { display: none; }
  .hero { padding-top: 6.5rem; }
  .case__visual { aspect-ratio: 4 / 3; }
}

/* ==========================================================================
   Case pages: problem first, then the evidence, the options, the decision
   ========================================================================== */
.chead { max-width: var(--maxw); margin-inline: auto; padding: clamp(7rem, 16vh, 10rem) var(--gutter) var(--s-5); }
.chead__title { font: 650 var(--fs-display)/1.05 var(--font-display); font-stretch: 92%; letter-spacing: -.012em; text-wrap: balance; max-width: 18ch; }
.chead__sub { margin-top: var(--s-3); max-width: 54ch; color: var(--text-2); font-size: var(--fs-lead); }
.chead__grid { margin-top: var(--s-5); display: grid; grid-template-columns: repeat(12, minmax(0, 1fr)); gap: var(--s-4); align-items: start; }
.facts { grid-column: 1 / 8; display: grid; }
.facts > div { display: grid; grid-template-columns: 9rem minmax(0, 1fr); gap: var(--s-2); padding: .85rem 0; border-top: 1px solid var(--line); }
.facts > div:last-child { border-bottom: 1px solid var(--line); }
.facts dt, .matrix th, .note dt { font-size: var(--fs-label); font-weight: 700; letter-spacing: .08em; text-transform: uppercase; color: var(--text-2); }
.facts dd { font-size: var(--fs-body); }
.sure { grid-column: 9 / 13; padding: var(--s-3); border: 1px solid var(--line-strong); border-radius: var(--radius-m); }
.sure h2 { font-size: var(--fs-label); font-weight: 700; letter-spacing: .08em; text-transform: uppercase; color: var(--text-2); }
.sure p { margin-top: .5rem; font-size: 1rem; line-height: 1.6; }
.sure p + p { margin-top: .75rem; }

.wide { max-width: var(--maxw); margin: var(--s-4) auto 0; padding-inline: var(--gutter); }
.wide img, .wide video { width: 100%; border-radius: var(--radius-m); background: #08090a; }
.wide figcaption, .fig figcaption { margin-top: var(--s-2); color: var(--text-2); font-size: var(--fs-small); max-width: 70ch; }

.chapter {
  max-width: var(--maxw); margin: var(--s-6) auto 0; padding: var(--s-6) var(--gutter) 0; border-top: 1px solid var(--line);
  display: grid; grid-template-columns: repeat(12, minmax(0, 1fr)); gap: var(--s-4);
}
.chapter__head { grid-column: 1 / 5; align-self: start; position: sticky; top: 5.5rem; }
.chapter__head h2 { font: 650 clamp(1.75rem, 3vw, 2.5rem)/1.12 var(--font-display); font-stretch: 92%; letter-spacing: -.01em; text-wrap: balance; }
.chapter__lede { margin-top: var(--s-2); color: var(--text-2); font-size: var(--fs-lead); }
.chapter__body { grid-column: 6 / 13; display: grid; gap: var(--s-5); min-width: 0; }
.prose { display: grid; gap: var(--s-2); }
.prose p { max-width: 62ch; font-size: 1.125rem; line-height: 1.7; }
.prose .muted { color: var(--text-2); }
.rows { border-bottom: 1px solid var(--line); }
.rows li { display: grid; grid-template-columns: 11rem minmax(0, 1fr); gap: var(--s-1) var(--s-3); padding: var(--s-2) 0; border-top: 1px solid var(--line); align-items: baseline; }
.rows__k { font: 650 clamp(1.5rem, 2.4vw, 2rem)/1.15 var(--font-display); font-stretch: 92%; letter-spacing: -.01em; }
.rows__v { font-size: 1rem; line-height: 1.6; }
.rows__v b { display: block; font-weight: 700; }
.rows__v .rc { display: block; margin-top: .5rem; color: var(--text-2); }
.rows__v .rc strong { color: var(--text); }
.fig img { width: 100%; border-radius: var(--radius-m); background: #08090a; }
.fig--phone img { max-width: 22rem; margin-inline: auto; }
.fig--phone { padding: var(--s-4); border-radius: var(--radius-m); background: #08090a; }
.fig--phone img { background: none; }

.note { padding: var(--s-3); border: 1px solid var(--line-strong); border-radius: var(--radius-m); }
.note h3 { font-size: var(--fs-label); font-weight: 700; letter-spacing: .08em; text-transform: uppercase; color: var(--text-2); }
.note p { margin-top: .5rem; font-size: 1rem; line-height: 1.6; }

.callout { font: 600 clamp(1.5rem, 2.5vw, 2.125rem)/1.25 var(--font-display); font-stretch: 92%; letter-spacing: -.01em; text-wrap: balance; padding-block: var(--s-3); border-block: 1px solid var(--line); }
:lang(vi) .callout, :lang(vi) .chead__title { line-height: 1.3; }
:lang(vi) .chead__title { line-height: 1.16; }

/* 5 Whys, drawn as a chain */
.why { position: relative; display: grid; gap: var(--s-3); padding-left: 2.25rem; counter-reset: why; }
.why::before { content: ""; position: absolute; left: .55rem; top: .6rem; bottom: .6rem; width: 2px; background: var(--line-strong); }
.why li { position: relative; counter-increment: why; }
.why li::before { content: ""; position: absolute; left: -2.25rem; top: .45rem; width: 1.15rem; height: 1.15rem; border-radius: 50%; background: var(--surface-1); border: 2px solid var(--text-2); }
.why li:last-child::before { background: var(--mark); border-color: var(--mark); }
.why__q { font-weight: 700; }
.why__a { margin-top: .15rem; color: var(--text-2); }

/* tables */
.scroll { overflow-x: auto; }
.scroll:focus-visible { outline: 2px solid var(--mark, #ffd43b); outline-offset: 4px; }
@media (max-width: 40rem) { .scroll { -webkit-mask-image: linear-gradient(90deg,#000 88%,transparent); mask-image: linear-gradient(90deg,#000 88%,transparent); } }
.matrix { width: 100%; border-collapse: collapse; font-size: var(--fs-small); min-width: 38rem; }
.matrix th, .matrix td { text-align: left; padding: var(--s-2) var(--s-2) var(--s-2) 0; border-bottom: 1px solid var(--line); vertical-align: top; }
.matrix td { line-height: 1.5; }
.matrix td:first-child { font: 650 1.125rem/1.3 var(--font-display); letter-spacing: -.005em; white-space: nowrap; }

/* two options */
.pair { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: var(--s-3); }
.opt { padding: var(--s-3); border: 1px solid var(--line); border-radius: var(--radius-m); }
.opt--chosen { border-color: var(--mark); }
.opt h3 { font: 650 1.375rem/1.2 var(--font-display); letter-spacing: -.005em; display: flex; flex-wrap: wrap; gap: .5rem .75rem; align-items: center; }
.opt p { margin-top: var(--s-1); color: var(--text-2); }
.opt h4 { margin: var(--s-2) 0 .25rem; font-size: var(--fs-label); font-weight: 700; letter-spacing: .08em; text-transform: uppercase; color: var(--text-2); }
.opt ul { display: grid; gap: .25rem; font-size: 1rem; }
.opt li::before { content: "–"; margin-right: .5rem; color: var(--text-2); }
.pill { display: inline-block; padding: .1rem .65rem; border-radius: 999px; background: var(--mark); color: var(--mark-ink); font: 700 .875rem/1.5 var(--font-text); }

.steps { display: grid; counter-reset: step; }
.steps li { counter-increment: step; display: grid; grid-template-columns: 3rem minmax(0, 1fr); gap: var(--s-2); padding: var(--s-2) 0; border-top: 1px solid var(--line); }
.steps li::before { content: counter(step, decimal-leading-zero); font: 650 1.25rem/1.4 var(--font-display); color: var(--text-2); }
.steps b { display: block; }
.steps span { color: var(--text-2); }
.checklist { display: grid; gap: .5rem; }
.checklist li { display: grid; grid-template-columns: 1.5rem minmax(0, 1fr); gap: .5rem; line-height: 1.55; }
.checklist li::before { content: ""; width: .6rem; height: .6rem; margin-top: .55rem; background: var(--mark); border-radius: 2px; }

.next { max-width: var(--maxw); margin: var(--s-7) auto 0; padding-inline: var(--gutter); }
.next a {
  position: relative; isolation: isolate; display: block; padding: var(--s-5) var(--gutter); margin-inline: calc(var(--gutter) * -1);
  border-block: 1px solid var(--line); text-decoration: none; transition: color .3s var(--ease-out);
}
.next a::before { content: ""; position: absolute; inset: 0; z-index: -1; background: var(--mark); transform: scaleY(0); transform-origin: bottom; transition: transform .5s var(--ease-out); }
.next a:hover, .next a:focus-visible { color: var(--mark-ink); }
.next a:hover::before, .next a:focus-visible::before { transform: scaleY(1); }
.next a:focus-visible { outline: 2px solid var(--mark-ink); outline-offset: -8px; }
.next__label { font-size: var(--fs-label); font-weight: 700; letter-spacing: .08em; text-transform: uppercase; color: var(--text-2); transition: color .3s var(--ease-out); }
.next a:hover .next__label, .next a:focus-visible .next__label, .next a:hover .next__problem, .next a:focus-visible .next__problem { color: var(--mark-ink); }
.next__name { display: flex; align-items: center; gap: var(--s-2); margin-top: var(--s-1); font: 650 clamp(2.25rem, 6vw, 4.5rem)/1.05 var(--font-display); font-stretch: 92%; letter-spacing: -.012em; }
.next__problem { margin-top: var(--s-2); max-width: 48ch; color: var(--text-2); font-size: var(--fs-lead); transition: color .3s var(--ease-out); }

@media (prefers-reduced-motion: no-preference) {
  .chead__title .w > span { transform: translateY(112%); animation: rise 1s var(--ease-out) calc(var(--hero-delay) + var(--i) * 45ms) both; }
  .chead__title mark { animation: mark-sweep .9s var(--ease-io) calc(var(--hero-delay) + .9s) both; }
  .chead__sub, .chead__grid { animation: fade-up .9s var(--ease-out) calc(var(--hero-delay) + .5s) both; }
  @supports (animation-timeline: view()) {
    .chapter__head, .chapter__body > *, .wide { animation: lift linear both; animation-timeline: view(); animation-range: entry 5% entry 50%; }
    .chapter mark, .callout mark { animation: mark-sweep linear both; animation-timeline: view(); animation-range: entry 30% entry 90%; }
    .wide img { animation: unclip linear both; animation-timeline: view(); animation-range: entry 0% entry 60%; }
  }
}
@media (max-width: 62rem) {
  .facts, .sure { grid-column: 1 / -1; }
  .chapter__head, .chapter__body { grid-column: 1 / -1; position: static; }
  .pair { grid-template-columns: 1fr; }
  .rows li { grid-template-columns: 1fr; }
}
@media (max-width: 40rem) { .facts > div { grid-template-columns: 1fr; gap: .15rem; } }

/* ---------- Reduced motion: everything is simply present ---------- */
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  .loader { display: none !important; }
  *, *::before, *::after { animation: none !important; transition-duration: .01ms !important; }
}