/* ============================================================
   BigAI — Bigdata & AI (premium dark theme) — demo by vPage.vn
   ============================================================ */
:root{
  --c:#ef4444;--c2:#fb7185;--c3:#f97316;
  --bg:#0a0b12;--bg2:#0f1119;--card:#141725;--card2:#1a1e30;
  --line:rgba(255,255,255,.08);--line2:rgba(255,255,255,.14);
  --txt:#e8eaf2;--head:#fff;--mut:#9aa1b8;--mut2:#6e7589;
  --r:18px;--rl:26px;--maxw:1200px;
  --glow:0 14px 40px rgba(239,68,68,.35);--sh:0 20px 50px rgba(0,0,0,.45);
  --grad:linear-gradient(135deg,#ef4444,#f97316);
  --ff:"Be Vietnam Pro",system-ui,sans-serif;--fh:"Sora",system-ui,sans-serif;
}
*{margin:0;padding:0;box-sizing:border-box}
html{scroll-behavior:smooth;scroll-padding-top:84px}
body{font-family:var(--ff);background:var(--bg);color:var(--txt);line-height:1.75;-webkit-font-smoothing:antialiased;overflow-x:hidden}
img{max-width:100%;display:block}a{text-decoration:none;color:inherit}ul{list-style:none}
h1,h2,h3{font-family:var(--fh);line-height:1.1;letter-spacing:-.02em;color:var(--head);font-weight:700}
.container{max-width:var(--maxw);margin:0 auto;padding:0 24px}
.section{padding:100px 0;position:relative}
.grad-text{background:var(--grad);-webkit-background-clip:text;background-clip:text;-webkit-text-fill-color:transparent}
.eyebrow{display:inline-flex;align-items:center;gap:8px;font-weight:700;font-size:12.5px;letter-spacing:.14em;text-transform:uppercase;color:var(--c);padding:6px 14px;border:1px solid var(--line2);border-radius:999px;background:rgba(239,68,68,.08);margin-bottom:18px}
.head{text-align:center;max-width:680px;margin:0 auto 60px}
.head h2{font-size:clamp(30px,4.4vw,46px);margin-bottom:14px}
.head p{color:var(--mut);font-size:17px}
.btn{display:inline-flex;align-items:center;gap:9px;font-weight:600;font-size:15px;padding:14px 30px;border-radius:12px;border:none;cursor:pointer;transition:transform .2s,box-shadow .2s,background .2s,border-color .2s}
.btn-primary{background:var(--grad);color:#fff;box-shadow:var(--glow)}
.btn-primary:hover{transform:translateY(-2px);box-shadow:0 18px 46px rgba(239,68,68,.5)}
.btn-ghost{background:rgba(255,255,255,.04);color:var(--txt);border:1px solid var(--line2)}
.btn-ghost:hover{background:rgba(255,255,255,.09);transform:translateY(-2px)}
.reveal{opacity:0;transform:translateY(28px);transition:opacity .7s cubic-bezier(.2,.7,.2,1),transform .7s cubic-bezier(.2,.7,.2,1)}
.reveal.in{opacity:1;transform:none}
/* header */
.header{position:sticky;top:0;z-index:100;backdrop-filter:saturate(160%) blur(14px);background:rgba(10,11,18,.72);border-bottom:1px solid var(--line);transition:box-shadow .3s}
.header.scrolled{box-shadow:0 10px 30px rgba(0,0,0,.5)}
.nav{display:flex;align-items:center;justify-content:space-between;height:74px}
.brand{display:flex;align-items:center;gap:11px;font-family:var(--fh);font-weight:800;font-size:22px;color:#fff}
.brand .dot{width:36px;height:36px;border-radius:11px;background:var(--grad);display:grid;place-items:center;color:#fff;box-shadow:var(--glow)}
.menu{display:flex;align-items:center;gap:28px}
.menu a{color:var(--mut);font-weight:500;font-size:15px;transition:color .2s}.menu a:hover{color:#fff}
.nav-r{display:flex;align-items:center;gap:12px}
.lang{display:inline-flex;border:1px solid var(--line2);border-radius:999px;overflow:hidden;font-size:13px;font-weight:700}
.lang button{padding:6px 12px;background:transparent;color:var(--mut);border:none;cursor:pointer;transition:.2s}
.lang button.on{background:var(--grad);color:#fff}
.burger{display:none;flex-direction:column;gap:5px;background:none;border:none;cursor:pointer;padding:6px}
.burger span{width:24px;height:2px;background:#fff;border-radius:2px}
@media(max-width:920px){.menu{display:none;position:absolute;top:74px;left:0;right:0;flex-direction:column;background:var(--bg2);padding:14px 24px;gap:0;border-bottom:1px solid var(--line)}.menu.open{display:flex}.menu a{padding:13px 0;border-bottom:1px solid var(--line)}.burger{display:flex}.nav-r .btn{display:none}}
/* hero */
.hero{position:relative;overflow:hidden;padding:110px 0 96px;text-align:center}
.hero::before{content:"";position:absolute;width:760px;height:760px;left:50%;top:-340px;transform:translateX(-50%);background:radial-gradient(circle,rgba(239,68,68,.28),transparent 60%);pointer-events:none}
.hero::after{content:"";position:absolute;inset:0;background-image:linear-gradient(rgba(255,255,255,.045) 1px,transparent 1px),linear-gradient(90deg,rgba(255,255,255,.045) 1px,transparent 1px);background-size:50px 50px;-webkit-mask-image:radial-gradient(ellipse 80% 55% at 50% 0,#000 30%,transparent 75%);mask-image:radial-gradient(ellipse 80% 55% at 50% 0,#000 30%,transparent 75%)}
.hero-inner{position:relative;z-index:2;max-width:840px;margin:0 auto}
.hero h1{font-size:clamp(38px,6.4vw,70px);margin-bottom:22px}
.hero p{font-size:19px;color:var(--mut);margin-bottom:34px;max-width:600px;margin-left:auto;margin-right:auto}
.hero-cta{display:flex;gap:14px;justify-content:center;flex-wrap:wrap}
.hero-vis{position:relative;z-index:2;max-width:900px;margin:54px auto 0;border-radius:var(--rl);overflow:hidden;border:1px solid var(--line2);box-shadow:var(--sh)}
.hero-vis img{width:100%;display:block}
/* stats */
.stats{display:grid;grid-template-columns:repeat(4,1fr);gap:22px}
@media(max-width:760px){.stats{grid-template-columns:repeat(2,1fr)}}
.stat{background:var(--card);border:1px solid var(--line);border-radius:var(--r);padding:26px;text-align:center}
.stat b{font-family:var(--fh);font-size:34px;display:block;line-height:1}.stat span{color:var(--mut);font-size:14px;margin-top:6px;display:block}
/* features */
.grid3{display:grid;grid-template-columns:repeat(3,1fr);gap:24px}
@media(max-width:900px){.grid3{grid-template-columns:1fr}}
.feat{background:var(--card);border:1px solid var(--line);border-radius:var(--r);padding:32px;transition:transform .25s,border-color .25s,box-shadow .25s}
.feat:hover{transform:translateY(-6px);border-color:rgba(239,68,68,.5);box-shadow:var(--sh)}
.feat .ic{width:58px;height:58px;border-radius:15px;background:rgba(239,68,68,.12);border:1px solid var(--line2);display:grid;place-items:center;color:var(--c);margin-bottom:18px}
.feat h3{font-size:20px;margin-bottom:10px}.feat p{color:var(--mut);font-size:14.5px}
/* steps */
.steps{display:grid;grid-template-columns:repeat(3,1fr);gap:24px;counter-reset:s}
@media(max-width:900px){.steps{grid-template-columns:1fr}}
.step{position:relative;background:linear-gradient(180deg,var(--card2),var(--card));border:1px solid var(--line);border-radius:var(--r);padding:30px}
.step::before{counter-increment:s;content:"0" counter(s);font-family:var(--fh);font-weight:800;font-size:30px;background:var(--grad);-webkit-background-clip:text;background-clip:text;-webkit-text-fill-color:transparent;display:block;margin-bottom:12px}
.step h3{font-size:18px;margin-bottom:8px}.step p{color:var(--mut);font-size:14.5px}
/* about */
.about{display:grid;grid-template-columns:1fr 1fr;gap:56px;align-items:center}
@media(max-width:900px){.about{grid-template-columns:1fr}}
.about-media{border-radius:var(--rl);overflow:hidden;border:1px solid var(--line2);box-shadow:var(--sh);aspect-ratio:4/3.2}
.about-media img{width:100%;height:100%;object-fit:cover}
.about h2{font-size:clamp(28px,4vw,42px);margin-bottom:18px}.about p{color:var(--mut);margin-bottom:14px}
.chk{display:flex;flex-direction:column;gap:12px;margin-top:18px}
.chk li{display:flex;align-items:flex-start;gap:10px;color:var(--txt)}
.chk svg{color:var(--c);flex-shrink:0;margin-top:3px}
/* testimonials */
.testi-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:24px}
@media(max-width:900px){.testi-grid{grid-template-columns:1fr}}
.testi{background:var(--card);border:1px solid var(--line);border-radius:var(--r);padding:30px}
.testi .stars{color:#fbbf24;margin-bottom:12px;letter-spacing:2px}.testi p{margin-bottom:18px}
.testi .who{display:flex;align-items:center;gap:12px}.testi .av{width:46px;height:46px;border-radius:50%;background:var(--grad);display:grid;place-items:center;color:#fff;font-weight:700}
.testi .who b{display:block}.testi .who small{color:var(--mut)}
/* cta */
.cta-band{position:relative;overflow:hidden;background:linear-gradient(135deg,#1a1020,#0f1119);border:1px solid var(--line2);border-radius:var(--rl);padding:64px 40px;text-align:center}
.cta-band::before{content:"";position:absolute;width:500px;height:500px;border-radius:50%;left:50%;top:-260px;transform:translateX(-50%);background:radial-gradient(circle,rgba(239,68,68,.3),transparent 60%)}
.cta-band h2{position:relative;font-size:clamp(28px,4vw,44px);margin-bottom:14px}.cta-band p{position:relative;color:var(--mut);font-size:18px;margin-bottom:28px}
/* footer */
.footer{border-top:1px solid var(--line);padding:60px 0 30px;background:var(--bg2)}
.footer-grid{display:grid;grid-template-columns:2fr 1fr 1fr 1.2fr;gap:40px;margin-bottom:40px}
@media(max-width:900px){.footer-grid{grid-template-columns:1fr 1fr}}@media(max-width:560px){.footer-grid{grid-template-columns:1fr}}
.footer h4{color:#fff;font-family:var(--fh);font-size:17px;margin-bottom:16px}
.footer a{color:var(--mut);display:block;margin-bottom:10px}.footer a:hover{color:var(--c)}
.footer .soc{display:flex;gap:10px;margin-top:8px}.footer .soc a{width:40px;height:40px;border-radius:10px;background:rgba(255,255,255,.05);border:1px solid var(--line);display:grid;place-items:center;color:#fff}.footer .soc a:hover{background:var(--grad);border-color:transparent}
.footer-bot{border-top:1px solid var(--line);padding-top:24px;text-align:center;color:var(--mut2);font-size:14px}
/* vPage */
.vpage-badge{position:fixed;bottom:18px;left:18px;background:var(--card);border:1px solid var(--line2);border-radius:999px;padding:8px 14px;font-size:12px;color:var(--mut);box-shadow:var(--sh);z-index:90}.vpage-badge b{color:var(--c)}
.vpage-cta{position:fixed;bottom:18px;right:18px;z-index:90;background:linear-gradient(135deg,#5b4cf0,#0bb5d6);color:#fff;font-weight:700;font-size:14px;padding:12px 20px;border-radius:999px;box-shadow:0 12px 28px rgba(91,76,240,.45);transition:transform .2s}.vpage-cta:hover{transform:translateY(-2px)}
@media(max-width:560px){.vpage-badge{display:none}.vpage-cta{bottom:14px;right:14px;font-size:13px;padding:10px 16px}}