/* ==========================================================
   vuhuybao.com — Black & White, human-centered
   ========================================================== */
:root{
  --ink:#0a0a0a;
  --ink-2:#2b2b2b;
  --muted:#6b6b6b;
  --line:#e4e4e4;
  --paper:#ffffff;
  --paper-2:#f5f5f4;
  --max:1180px;
  --r:18px;
  --serif:"Playfair Display", Georgia, "Times New Roman", serif;
  --sans:"Be Vietnam Pro", system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
}
*{box-sizing:border-box;margin:0;padding:0}
html{scroll-behavior:smooth;-webkit-text-size-adjust:100%}
body{font-family:var(--sans);color:var(--ink);background:var(--paper);line-height:1.7;font-size:17px;overflow-x:hidden}
img{max-width:100%;display:block}
a{color:inherit;text-decoration:none}
.container{width:100%;max-width:var(--max);margin:0 auto;padding:0 24px}
.eyebrow{display:inline-flex;align-items:center;gap:10px;font-size:13px;letter-spacing:.18em;text-transform:uppercase;font-weight:600;color:var(--muted)}
.eyebrow::before{content:"";width:28px;height:1.5px;background:currentColor}
h1,h2,h3{line-height:1.2;font-weight:700;letter-spacing:-.01em}
h2.title{font-family:var(--serif);font-size:clamp(32px,4.4vw,52px);margin:14px 0 18px}
.lead{font-size:clamp(17px,1.6vw,20px);color:var(--ink-2);max-width:720px}
section{padding:110px 0}
.section-dark{background:var(--ink);color:#fff}
.section-dark .eyebrow{color:#a8a8a8}
.section-dark .lead{color:#d6d6d6}
.section-soft{background:var(--paper-2)}

/* Buttons */
.btn{display:inline-flex;align-items:center;gap:10px;padding:15px 26px;border-radius:999px;font-weight:600;font-size:15.5px;border:1.5px solid var(--ink);transition:.25s ease;cursor:pointer}
.btn-dark{background:var(--ink);color:#fff}
.btn-dark:hover{background:#fff;color:var(--ink)}
.btn-ghost{background:transparent;color:var(--ink)}
.btn-ghost:hover{background:var(--ink);color:#fff}
.section-dark .btn-light{background:#fff;color:var(--ink);border-color:#fff}
.section-dark .btn-light:hover{background:transparent;color:#fff}
.btn svg{width:18px;height:18px}

/* Header */
.header{position:sticky;top:0;z-index:50;background:rgba(255,255,255,.88);backdrop-filter:saturate(180%) blur(14px);-webkit-backdrop-filter:saturate(180%) blur(14px);border-bottom:1px solid transparent;transition:.3s}
.header.scrolled{border-bottom-color:var(--line)}
.nav{display:flex;align-items:center;justify-content:space-between;height:76px}
.brand{display:flex;align-items:center;gap:12px;font-weight:700;letter-spacing:.06em;font-size:15px}
.brand img{width:40px;height:40px}
.brand small{display:block;font-weight:500;letter-spacing:.02em;color:var(--muted);font-size:12px}
.menu{display:flex;align-items:center;gap:30px;list-style:none;font-size:15px;font-weight:500}
.menu a{position:relative;padding:6px 0}
.menu a:not(.btn)::after{content:"";position:absolute;left:0;bottom:0;width:0;height:1.5px;background:var(--ink);transition:.25s}
.menu a:not(.btn):hover::after{width:100%}
.menu .btn{padding:10px 20px;font-size:14px}
.burger{display:none;background:none;border:0;width:44px;height:44px;cursor:pointer}
.burger span{display:block;width:24px;height:2px;background:var(--ink);margin:5px auto;transition:.3s}

/* Hero */
.hero{padding:70px 0 90px;position:relative}
.hero-grid{display:grid;grid-template-columns:1.3fr .7fr;gap:60px;align-items:center}
.hero h1{font-family:var(--serif);font-size:clamp(40px,5vw,66px);line-height:1.04;margin:22px 0 26px;letter-spacing:-.02em}
.hero h1 .nw{white-space:nowrap}
@media (max-width:620px){.hero h1 .nw{white-space:normal}}
.hero h1 em{font-style:italic;font-weight:500}
.hero .lead{margin-bottom:36px}
.hero-cta{display:flex;flex-wrap:wrap;gap:14px}
.hero-photo{position:relative}
.hero-photo .frame{position:relative;border-radius:28px;overflow:hidden;background:var(--paper-2);aspect-ratio:3/4}
.hero-photo img{width:100%;height:100%;object-fit:cover;object-position:top}
.hero-photo .tag{position:absolute;left:-28px;bottom:42px;background:var(--ink);color:#fff;padding:16px 20px;border-radius:14px;font-size:14px;line-height:1.45;box-shadow:0 18px 40px rgba(0,0,0,.18)}
.hero-photo .tag b{display:block;font-size:16px}
.stats{display:grid;grid-template-columns:repeat(4,1fr);gap:0;border-top:1px solid var(--line);margin-top:80px}
.stat{padding:28px 22px 0 0}
.stat+.stat{padding-left:22px;border-left:1px solid var(--line)}
.stat b{display:block;font-family:var(--serif);font-size:clamp(28px,3vw,40px);line-height:1.1}
.stat span{font-size:14px;color:var(--muted)}

/* Philosophy */
.quote{font-family:var(--serif);font-size:clamp(28px,3.6vw,46px);line-height:1.25;max-width:960px;margin:22px 0 60px}
.quote em{font-style:italic;color:#9a9a9a}
.pillars3{display:grid;grid-template-columns:repeat(3,1fr);gap:1px;background:#2e2e2e;border:1px solid #2e2e2e;border-radius:var(--r);overflow:hidden}
.pillars3 .p{background:var(--ink);padding:38px 32px}
.pillars3 .num{font-family:var(--serif);font-size:15px;color:#8d8d8d;margin-bottom:26px}
.pillars3 h3{font-size:22px;margin-bottom:12px}
.pillars3 p{color:#c9c9c9;font-size:15.5px}

/* Model */
.model{display:grid;grid-template-columns:.9fr 1.1fr;gap:70px;align-items:center;margin-top:50px}
.model-diagram{position:relative;aspect-ratio:1;max-width:480px;width:100%;margin:0 auto}
.model-diagram .ring{position:absolute;inset:12%;border:1.5px dashed #bdbdbd;border-radius:50%}
.model-diagram .core{position:absolute;inset:34%;background:var(--ink);color:#fff;border-radius:50%;display:flex;flex-direction:column;align-items:center;justify-content:center;text-align:center;padding:10px}
.model-diagram .core b{font-family:var(--serif);font-size:clamp(18px,2.2vw,24px);line-height:1.15}
.model-diagram .core span{font-size:12px;letter-spacing:.14em;text-transform:uppercase;color:#bdbdbd;margin-top:6px}
.node{position:absolute;width:30%;aspect-ratio:1;border-radius:50%;background:#fff;border:1.5px solid var(--ink);display:flex;flex-direction:column;align-items:center;justify-content:center;text-align:center;font-weight:600;font-size:clamp(12px,1.3vw,15px);line-height:1.25;padding:8px;transition:.3s}
.node small{font-weight:500;color:var(--muted);font-size:11px;letter-spacing:.1em}
.node:hover{background:var(--ink);color:#fff}
.node:hover small{color:#bbb}
.n1{top:-3%;left:35%}.n2{top:35%;right:-3%}.n3{bottom:-3%;left:35%}.n4{top:35%;left:-3%}
.model-list{list-style:none;display:grid;gap:4px}
.model-list li{display:grid;grid-template-columns:56px 1fr;gap:18px;padding:22px 0;border-bottom:1px solid var(--line)}
.model-list li:first-child{border-top:1px solid var(--line)}
.model-list .k{font-family:var(--serif);font-size:28px;line-height:1}
.model-list h3{font-size:19px;margin-bottom:4px}
.model-list p{color:var(--ink-2);font-size:15.5px}

/* Lean Six Sigma */
.lss-head{display:grid;grid-template-columns:1fr 1fr;gap:60px;align-items:end}
.dmaic{display:grid;grid-template-columns:repeat(5,1fr);gap:14px;margin-top:60px;counter-reset:s}
.step{border:1.5px solid var(--ink);border-radius:var(--r);padding:26px 22px 28px;background:#fff;position:relative;transition:.3s}
.step:hover{background:var(--ink);color:#fff;transform:translateY(-4px)}
.step:hover p{color:#cfcfcf}
.step .letter{font-family:var(--serif);font-size:54px;line-height:1;font-weight:700}
.step h3{font-size:17px;margin:14px 0 8px}
.step p{font-size:14.5px;color:var(--ink-2);line-height:1.6}
.wastes-wrap{margin-top:90px;display:grid;grid-template-columns:.8fr 1.2fr;gap:60px;align-items:start}
.wastes-wrap h3.sub{font-family:var(--serif);font-size:clamp(26px,3vw,36px);margin:12px 0 14px}
.wastes{display:grid;grid-template-columns:repeat(2,1fr);gap:1px;background:var(--line);border:1px solid var(--line);border-radius:var(--r);overflow:hidden}
.waste{background:#fff;padding:20px 22px;display:grid;grid-template-columns:40px 1fr;gap:12px;align-items:start}
.waste b{font-family:var(--serif);font-size:26px;line-height:1}
.waste h4{font-size:15.5px}
.waste p{font-size:14px;color:var(--muted);line-height:1.55}
.tools{display:flex;flex-wrap:wrap;gap:10px;margin-top:26px}
.chip{border:1px solid var(--ink);border-radius:999px;padding:7px 14px;font-size:13.5px;font-weight:500}

/* Services */
.services{display:grid;grid-template-columns:repeat(2,1fr);gap:20px;margin-top:56px}
.svc{border:1px solid #2e2e2e;border-radius:var(--r);padding:36px 34px;transition:.3s;position:relative}
.svc:hover{background:#fff;color:var(--ink)}
.svc:hover p,.svc:hover li{color:var(--ink-2)}
.svc .idx{font-size:13px;letter-spacing:.16em;color:#8d8d8d;font-weight:600}
.svc h3{font-family:var(--serif);font-size:26px;margin:14px 0 10px}
.svc p{color:#c9c9c9;font-size:15.5px;margin-bottom:14px}
.svc ul{list-style:none;display:grid;gap:6px}
.svc li{font-size:14.5px;color:#bdbdbd;padding-left:20px;position:relative}
.svc li::before{content:"—";position:absolute;left:0}
.industries{display:flex;flex-wrap:wrap;gap:10px;margin-top:40px;align-items:center}
.industries span.label{font-size:14px;color:#a8a8a8;margin-right:6px}
.industries .chip{border-color:#555;color:#e5e5e5}

/* Articles */
.articles{display:grid;grid-template-columns:repeat(3,1fr);gap:24px;margin-top:56px}
.card{display:flex;flex-direction:column;border:1px solid var(--line);border-radius:var(--r);overflow:hidden;background:#fff;transition:.3s}
.card:hover{border-color:var(--ink);transform:translateY(-4px);box-shadow:0 20px 40px rgba(0,0,0,.08)}
.card .cover{aspect-ratio:16/10;background:var(--ink);color:#fff;display:flex;align-items:flex-end;padding:24px;position:relative;overflow:hidden}
.card .cover.alt{background:#fff;color:var(--ink);border-bottom:1px solid var(--line)}
.card .cover.mid{background:#3a3a3a}
.card .cover .big{font-family:var(--serif);font-size:64px;line-height:.9;font-weight:700;opacity:.95}
.card .cover .pattern{position:absolute;inset:0;background-image:radial-gradient(currentColor 1px,transparent 1.5px);background-size:18px 18px;opacity:.14}
.card .body{padding:24px 24px 28px;display:flex;flex-direction:column;gap:10px;flex:1}
.card .meta{font-size:12.5px;letter-spacing:.12em;text-transform:uppercase;color:var(--muted);font-weight:600}
.card h3{font-size:20px;line-height:1.35}
.card p{font-size:15px;color:var(--ink-2)}
.card .more{margin-top:auto;font-weight:600;font-size:14.5px;display:inline-flex;gap:8px;align-items:center}
.tool-banner{margin-top:28px;border:1.5px solid var(--ink);border-radius:var(--r);padding:28px 32px;display:flex;justify-content:space-between;align-items:center;gap:24px;flex-wrap:wrap}
.tool-banner h3{font-size:20px}
.tool-banner p{color:var(--ink-2);font-size:15px}

/* Profile */
.profile{display:grid;grid-template-columns:.8fr 1.2fr;gap:70px;align-items:start}
.profile-photo{position:sticky;top:110px}
.profile-photo .frame{border-radius:28px;overflow:hidden;background:var(--paper-2);aspect-ratio:3/4}
.profile-photo img{width:100%;height:100%;object-fit:cover;object-position:top}
.profile-photo .name{margin-top:20px;font-family:var(--serif);font-size:28px;font-weight:700}
.profile-photo .role{color:var(--muted);font-size:15px}
.creds{display:flex;flex-wrap:wrap;gap:10px;margin:28px 0 10px}
.timeline{list-style:none;margin-top:40px;position:relative}
.timeline::before{content:"";position:absolute;left:7px;top:8px;bottom:8px;width:1.5px;background:var(--line)}
.timeline li{position:relative;padding:0 0 34px 44px}
.timeline li::before{content:"";position:absolute;left:0;top:7px;width:16px;height:16px;border-radius:50%;background:#fff;border:2px solid var(--ink)}
.timeline li.now::before{background:var(--ink)}
.timeline .when{font-size:12.5px;letter-spacing:.14em;text-transform:uppercase;font-weight:600;color:var(--muted)}
.timeline h3{font-size:19px;margin:4px 0 4px}
.timeline p{color:var(--ink-2);font-size:15.5px}

/* Contact */
.contact{text-align:center}
.contact h2.title{max-width:820px;margin-left:auto;margin-right:auto}
.contact .lead{margin:0 auto 40px}
.contact-cta{display:flex;gap:14px;justify-content:center;flex-wrap:wrap}
.contact-info{margin-top:50px;display:flex;justify-content:center;gap:40px;flex-wrap:wrap;color:#bdbdbd;font-size:15px}
.contact-info a{color:#fff;border-bottom:1px solid #555}

/* Footer */
.footer{background:var(--ink);color:#9a9a9a;border-top:1px solid #222;padding:34px 0;font-size:14px}
.footer .row{display:flex;justify-content:space-between;align-items:center;gap:20px;flex-wrap:wrap}
.footer .brand{color:#fff}
.footer .brand img{filter:invert(1)}

/* Article page */
.article-hero{padding:80px 0 40px;border-bottom:1px solid var(--line)}
.article-hero h1{font-family:var(--serif);font-size:clamp(34px,5vw,58px);line-height:1.12;margin:18px 0 18px;max-width:900px}
.article-hero .meta{color:var(--muted);font-size:15px}
.prose{max-width:740px;margin:0 auto;padding:60px 24px 100px;font-size:18px}
.prose h2{font-family:var(--serif);font-size:30px;margin:48px 0 14px}
.prose h3{font-size:21px;margin:32px 0 10px}
.prose p{margin:0 0 20px;color:#1f1f1f}
.prose ul,.prose ol{margin:0 0 22px 24px}
.prose li{margin-bottom:8px}
.prose blockquote{border-left:3px solid var(--ink);padding:6px 0 6px 22px;margin:30px 0;font-family:var(--serif);font-size:24px;line-height:1.4;font-style:italic}
.prose table{width:100%;border-collapse:collapse;margin:10px 0 26px;font-size:15.5px}
.prose th,.prose td{border:1px solid var(--line);padding:10px 12px;text-align:left;vertical-align:top}
.prose th{background:var(--ink);color:#fff;font-weight:600}
.prose .note{background:var(--paper-2);border-radius:14px;padding:20px 22px;font-size:16px}
.back{display:inline-flex;gap:8px;align-items:center;font-weight:600;font-size:15px}

/* Reveal */
.reveal{opacity:0;transform:translateY(26px);transition:opacity .8s ease,transform .8s ease}
.reveal.in{opacity:1;transform:none}
@media (prefers-reduced-motion:reduce){.reveal{opacity:1;transform:none;transition:none}html{scroll-behavior:auto}}

/* Responsive */
@media (max-width:1024px){
  .dmaic{grid-template-columns:repeat(3,1fr)}
  .articles{grid-template-columns:repeat(2,1fr)}
}
@media (max-width:900px){
  section{padding:80px 0}
  .menu{position:fixed;inset:76px 0 auto 0;background:#fff;flex-direction:column;align-items:flex-start;gap:0;padding:10px 24px 26px;border-bottom:1px solid var(--line);transform:translateY(-130%);transition:.35s;z-index:40}
  .menu.open{transform:none}
  .menu li{width:100%}
  .menu a{display:block;padding:14px 0;border-bottom:1px solid var(--line)}
  .menu a.btn{margin-top:16px;display:inline-flex;border-bottom:1.5px solid var(--ink)}
  .burger{display:block}
  .burger.x span:nth-child(1){transform:translateY(7px) rotate(45deg)}
  .burger.x span:nth-child(2){opacity:0}
  .burger.x span:nth-child(3){transform:translateY(-7px) rotate(-45deg)}
  .hero-grid,.model,.lss-head,.wastes-wrap,.profile{grid-template-columns:1fr;gap:44px}
  .hero-photo{max-width:420px;margin:0 auto;width:100%}
  .hero-photo .tag{left:12px}
  .stats{grid-template-columns:repeat(2,1fr);margin-top:56px}
  .stat:nth-child(3){border-left:0;padding-left:0}
  .stat{padding-bottom:22px}
  .pillars3,.services{grid-template-columns:1fr}
  .profile-photo{position:static;max-width:380px}
}
@media (max-width:620px){
  .container{padding:0 16px}
  body{font-size:16px}
  .dmaic,.articles,.wastes{grid-template-columns:1fr}
  .svc{padding:28px 24px}
  .brand small{display:none}
  .prose{font-size:17px;padding:44px 16px 80px}
  .tool-banner{padding:24px}
  .stat b{font-size:24px}
}

/* Wordmark (header/footer) */
.brand{gap:14px;align-items:center}
.wm{font-family:"Roboto Slab",Georgia,serif;font-weight:900;font-size:26px;letter-spacing:-.015em;line-height:1;color:var(--ink);white-space:nowrap}
.wm-tag{display:inline-flex;align-items:center;gap:8px;font-family:var(--sans);font-weight:700;font-size:15px;letter-spacing:.04em;color:#6b6b6b;white-space:nowrap}
.wm-tag::before{content:"";width:6px;height:6px;border-radius:50%;background:currentColor}
.header{border-bottom:3px solid var(--ink)!important}
.footer .wm{color:#fff}
.footer .wm-tag{color:#9a9a9a}
@media (max-width:620px){.wm{font-size:22px}.wm-tag{font-size:13px}}

/* Tools */
.tools-grid{display:grid;grid-template-columns:repeat(4,1fr);gap:18px;margin-top:56px}
.tool{display:flex;flex-direction:column;gap:12px;background:#fff;border:1.5px solid var(--ink);border-radius:var(--r);padding:26px 24px 24px;transition:.3s}
.tool:hover{background:var(--ink);color:#fff;transform:translateY(-4px)}
.tool:hover p,.tool:hover li{color:#cfcfcf}
.tool:hover .tool-phase{border-color:#fff;color:#fff}
.tool-top{display:flex;justify-content:space-between;align-items:center}
.tool-code{font-family:var(--serif);font-weight:700;font-size:30px;line-height:1}
.tool-phase{font-size:11.5px;letter-spacing:.14em;text-transform:uppercase;font-weight:700;border:1px solid var(--ink);border-radius:999px;padding:4px 10px}
.tool h3{font-size:19px;margin-top:8px}
.tool p{font-size:14.5px;color:var(--ink-2);line-height:1.6}
.tool ul{list-style:none;display:grid;gap:4px;margin-bottom:6px}
.tool li{font-size:13.5px;color:var(--muted);padding-left:18px;position:relative}
.tool li::before{content:"✓";position:absolute;left:0;font-weight:700}
.tool-go{margin-top:auto;display:inline-flex;align-items:center;gap:8px;font-weight:700;font-size:14.5px}
.tool-go svg{width:16px;height:16px}

/* Booking */
.booking{margin-top:10px}
.booking-frame{display:none}
.booking.has-url .booking-frame{display:block;background:#fff;border-radius:var(--r);overflow:hidden;max-width:980px;margin:0 auto 26px;box-shadow:0 20px 60px rgba(0,0,0,.35)}
.booking-frame iframe{display:block;width:100%;height:680px;border:0}
@media (max-width:1024px){.tools-grid{grid-template-columns:repeat(2,1fr)}}
@media (max-width:620px){.tools-grid{grid-template-columns:1fr}.booking-frame iframe{height:760px}}
.node{font-size:clamp(11px,1.15vw,14px);line-height:1.2}
.n1{font-size:clamp(10px,1vw,12.5px)}

/* Press */
.press-strip{margin-top:36px;display:flex;flex-wrap:wrap;align-items:center;gap:10px 26px;padding:18px 24px;border:1.5px solid var(--ink);border-radius:999px;transition:.25s}
.press-strip:hover{background:var(--ink);color:#fff}
.press-strip:hover .ps-label{color:#bbb}
.ps-label{font-size:12.5px;letter-spacing:.16em;text-transform:uppercase;font-weight:700;color:var(--muted)}
.ps-name{font-family:"Roboto Slab",Georgia,serif;font-weight:800;font-size:19px}
.ps-go{margin-left:auto;font-weight:700;font-size:14.5px}
.press{background:var(--paper-2)}
.press-grid{display:grid;grid-template-columns:repeat(2,1fr);gap:22px;margin-top:50px}
.press-card{display:flex;flex-direction:column;gap:16px;background:#fff;border:1.5px solid var(--ink);border-radius:var(--r);padding:32px 32px 28px;transition:.3s}
.press-card:hover{background:var(--ink);color:#fff;transform:translateY(-4px)}
.press-card:hover .pc-date,.press-card:hover blockquote{color:#cfcfcf}
.press-card:hover blockquote{border-color:#fff}
.pc-head{display:flex;justify-content:space-between;align-items:baseline;gap:12px;padding-bottom:14px;border-bottom:1px solid currentColor}
.pc-outlet{font-family:"Roboto Slab",Georgia,serif;font-weight:900;font-size:24px;line-height:1.1}
.pc-date{font-size:13px;letter-spacing:.1em;font-weight:600;color:var(--muted);white-space:nowrap}
.press-card h3{font-size:20px;line-height:1.4}
.press-card blockquote{font-family:var(--serif);font-style:italic;font-size:19px;line-height:1.5;color:var(--ink-2);border-left:3px solid var(--ink);padding-left:16px}
.pc-go{margin-top:auto;display:inline-flex;align-items:center;gap:8px;font-weight:700;font-size:14.5px}
.pc-go svg{width:16px;height:16px}
@media (max-width:900px){.press-grid{grid-template-columns:1fr}.press-strip{border-radius:18px}.ps-go{margin-left:0}}
@media (max-width:620px){.press-card{padding:24px 22px}.pc-outlet{font-size:20px}}

/* Epigraph */
.epigraph{margin:0 0 34px;padding:4px 0 4px 20px;border-left:3px solid var(--ink);max-width:560px}
.epigraph blockquote{font-family:var(--serif);font-style:italic;font-size:clamp(17px,1.5vw,20px);line-height:1.5;color:var(--ink-2)}
.epigraph figcaption{margin-top:8px;font-size:13px;letter-spacing:.14em;text-transform:uppercase;font-weight:700;color:var(--muted)}
.epigraph figcaption::before{content:"— "}

/* B mark inside wordmark */
.wm{display:inline-flex;align-items:baseline}
.wm-b{width:.98em;height:.98em;margin:0 .04em 0 .28em;align-self:center;transform:translateY(.02em);flex:none}
.wm-b .wb-bg{fill:#0a0a0a}
.wm-b .wb-fg{stroke:#fff}
.wm-b .wb-dot{fill:#fff}
.footer .wm-b .wb-bg{fill:#fff}
.footer .wm-b .wb-fg{stroke:#0a0a0a}
.footer .wm-b .wb-dot{fill:#0a0a0a}
.timeline p a{border-bottom:1px solid currentColor}
/* 5 stats */
.stats{grid-template-columns:repeat(5,1fr)}
.stat b{font-size:clamp(26px,2.6vw,36px)}
.stat span{font-size:13.5px;line-height:1.5;display:block;margin-top:4px}
@media (max-width:900px){
  .stats{grid-template-columns:repeat(2,1fr)}
  .stat:nth-child(odd){border-left:0;padding-left:0}
  .stat:nth-child(even){border-left:1px solid var(--line);padding-left:22px}
  .stat:last-child{grid-column:1/-1}
}