:root{
  --brand:#b91c1c; --brand-2:#dc2626; --brand-dark:#450a0a; --accent:#f59e0b;
  --ink:#2b1a1a; --muted:#6b5555; --bg:#fdf7f6; --card:#ffffff;
  --line:#eadcdc; --radius:14px; --maxw:1120px;
}
*{box-sizing:border-box}
html{scroll-behavior:smooth}
body{margin:0;font-family:'Segoe UI',system-ui,-apple-system,Roboto,'Helvetica Neue',Arial,sans-serif;color:var(--ink);background:var(--bg);line-height:1.65;font-size:16px}
img{max-width:100%;height:auto;display:block}
a{color:var(--brand)}
.wrap{max-width:var(--maxw);margin:0 auto;padding:0 20px}
header.site{position:sticky;top:0;z-index:50;background:rgba(255,255,255,.94);backdrop-filter:blur(6px);border-bottom:1px solid var(--line)}
.nav{display:flex;align-items:center;gap:24px;height:60px}
.logo{display:flex;align-items:center;gap:8px;font-weight:800;font-size:20px;color:var(--brand);text-decoration:none}
.logo .dot{width:26px;height:26px;border-radius:8px;background:var(--brand);color:#fff;display:grid;place-items:center;font-size:14px}
.nav a.link{text-decoration:none;color:var(--ink);font-weight:600;font-size:15px;padding:6px 2px;border-bottom:2px solid transparent}
.nav a.link:hover{border-color:var(--brand)}
.nav .grow{flex:1}
.btn{display:inline-block;text-decoration:none;font-weight:700;border-radius:10px;padding:11px 22px;transition:.15s}
.btn-primary{background:var(--brand);color:#fff}
.btn-primary:hover{background:var(--brand-2)}
.btn-outline{border:2px solid var(--brand);color:var(--brand)}
.btn-outline:hover{background:var(--brand);color:#fff}
.btn-cta{background:var(--accent);color:#3b2600}
.btn-cta:hover{filter:brightness(1.06)}
.hero{background:linear-gradient(160deg,#450a0a 0%,#991b1b 55%,#dc2626 100%);color:#fff;padding:72px 0 84px}
.hero h1{font-size:clamp(30px,4.6vw,46px);line-height:1.18;margin:0 0 16px;font-weight:800}
.hero p.sub{font-size:clamp(16px,2vw,19px);max-width:640px;opacity:.92;margin:0 0 28px}
.hero .cta-row{display:flex;gap:14px;flex-wrap:wrap}
.hero .tag{display:inline-block;background:rgba(255,255,255,.14);border:1px solid rgba(255,255,255,.25);border-radius:999px;padding:5px 14px;font-size:13.5px;font-weight:600;margin-bottom:22px}
.hero-shot{margin-top:52px;border-radius:var(--radius);overflow:hidden;box-shadow:0 24px 60px rgba(0,0,0,.35);border:1px solid rgba(255,255,255,.2)}
section{padding:64px 0}
section h2{font-size:clamp(24px,3.2vw,32px);margin:0 0 8px;font-weight:800}
section .lead{color:var(--muted);max-width:720px;margin:0 0 36px}
.grid{display:grid;gap:20px}
.g3{grid-template-columns:repeat(auto-fit,minmax(280px,1fr))}
.g2{grid-template-columns:repeat(auto-fit,minmax(340px,1fr))}
.card{background:var(--card);border:1px solid var(--line);border-radius:var(--radius);padding:24px}
.card h3{margin:0 0 8px;font-size:18px}
.card p{margin:0;color:var(--muted);font-size:15px}
.card .ico{font-size:26px;margin-bottom:12px;display:block}
.shot{background:var(--card);border:1px solid var(--line);border-radius:var(--radius);overflow:hidden}
.shot img{width:100%}
.shot figcaption{padding:12px 16px;font-size:14.5px;color:var(--muted)}
.shot figcaption b{color:var(--ink)}
.models .card{display:flex;flex-direction:column;gap:14px;padding:30px}
.models .badge{align-self:flex-start;background:#fdecec;color:var(--brand);font-weight:700;font-size:13px;border-radius:999px;padding:4px 14px}
.models ul{margin:0;padding-left:20px;color:var(--muted);font-size:15px}
.models .price{font-size:22px;font-weight:800;color:var(--ink)}
.models .price small{font-weight:500;font-size:13.5px;color:var(--muted)}
.models .btn{margin-top:auto;text-align:center}
.faq details{background:var(--card);border:1px solid var(--line);border-radius:10px;padding:16px 20px;margin-bottom:10px}
.faq summary{font-weight:700;cursor:pointer}
.faq p{margin:10px 0 0;color:var(--muted)}
.cta-band{background:linear-gradient(150deg,#991b1b,#dc2626);color:#fff;border-radius:var(--radius);padding:44px 36px;text-align:center}
.cta-band h2{color:#fff}
.cta-band p{opacity:.9;max-width:560px;margin:8px auto 24px}
footer.site{background:#2b0a0a;color:#e6cfcf;padding:40px 0;font-size:14.5px}
footer.site a{color:#e6cfcf}
footer .cols{display:grid;grid-template-columns:repeat(auto-fit,minmax(220px,1fr));gap:24px}
/* guide pages */
.guide-hero{background:linear-gradient(160deg,#450a0a,#991b1b);color:#fff;padding:48px 0}
.guide-hero h1{margin:0 0 10px;font-size:clamp(26px,3.6vw,36px)}
.guide-hero p{margin:0;opacity:.92;max-width:760px}
.toc{background:var(--card);border:1px solid var(--line);border-radius:var(--radius);padding:22px 26px;margin:-34px auto 0;position:relative;box-shadow:0 10px 30px rgba(0,0,0,.08)}
.toc h2{font-size:16px;margin:0 0 10px}
.toc ol{margin:0;padding-left:22px;columns:2;column-gap:40px;font-size:15px}
.toc a{text-decoration:none}
.step{padding:48px 0;border-bottom:1px solid var(--line)}
.step:last-of-type{border-bottom:none}
.step .kicker{color:var(--brand);font-weight:800;font-size:14px;letter-spacing:.06em;text-transform:uppercase}
.step h2{margin:6px 0 12px}
.step h3{margin:18px 0 8px;font-size:17px}
.step .body{display:grid;grid-template-columns:1fr 1.25fr;gap:32px;align-items:start}
.step .body p{margin:0 0 12px;color:#463535}
.step ul{margin:0 0 12px;padding-left:20px;color:#463535}
.step figure{margin:0}
.step figure img{border:1px solid var(--line);border-radius:10px;box-shadow:0 8px 24px rgba(0,0,0,.08)}
.step figcaption{font-size:13.5px;color:var(--muted);margin-top:8px;text-align:center}
.tip{background:#fff8e6;border:1px solid #f2dfae;border-radius:10px;padding:12px 16px;font-size:14.5px;margin-top:8px}
.flow-diagram{display:flex;flex-wrap:wrap;gap:8px;align-items:center;margin:18px 0 0}
.flow-diagram span{background:#fceaea;color:var(--brand);font-weight:700;font-size:13.5px;border-radius:8px;padding:7px 13px}
.flow-diagram i{color:var(--muted);font-style:normal}
/* bảng chọn 3 công tắc của mô hình đầy đủ (2.1–2.6) */
.switch-grid table{width:100%;border-collapse:collapse;font-size:14.5px;background:var(--card)}
.switch-grid th,.switch-grid td{border:1px solid var(--line);padding:10px 12px;text-align:center}
.switch-grid th{background:#fbeaea;color:var(--brand);font-weight:800}
.switch-grid td:first-child,.switch-grid th:first-child{text-align:left;font-weight:700;color:var(--ink)}
.switch-grid .on{color:var(--brand);font-weight:800}
.switch-grid .off{color:var(--muted)}
.switch-grid caption{caption-side:top;text-align:left;font-size:14px;color:var(--muted);padding-bottom:8px}
@media (max-width:860px){
  .step .body{grid-template-columns:1fr}
  .toc ol{columns:1}
  .nav{gap:14px}
  .nav a.link{display:none}
}