:root{
  --ink:#0b1220;--muted:#657085;--paper:#ffffff;--line:#e6eaf0;
  --brand:#7c3aed;--brand-ink:#5b21b6;--soft:#f5f3ff;
  --r:16px;--sh:0 12px 26px rgba(11,18,32,.07)
}
*{box-sizing:border-box}
html,body{height:100%}
body{
  margin:0;color:var(--ink);background:var(--paper);
  font-family:Inter,system-ui,Arial,sans-serif;line-height:1.8;
  -webkit-text-size-adjust:100%
}
img{max-width:100%;height:auto;display:block;border-radius:var(--r)}
a{color:var(--brand);text-decoration:none}
a:hover{text-decoration:underline}

/* ---------- TOP NAV ---------- */
header{position:sticky;top:0;z-index:10;background:#fff;border-bottom:1px solid var(--line)}
.nav{
  width:min(1140px,94%);margin:0 auto;padding:.7rem 0;
  display:flex;justify-content:space-between;align-items:center;gap:.6rem;
  flex-wrap:wrap; /* cho mobile */
}
.nav a{margin-left:.5rem;padding:.55rem .85rem;border-radius:999px}
.nav a:hover{background:var(--soft);text-decoration:none}

/* ---------- CONTAINER ---------- */
.wrap{width:min(980px,92%);margin:0 auto}

/* ---------- HERO (CENTERED) ---------- */
.hero{background:linear-gradient(180deg,var(--soft),#fff 60%);border-bottom:1px solid var(--line)}
.hero .wrap{
  text-align:center;padding:1.2rem 0;display:grid;gap:.9rem;justify-items:center
}
.hero h1{font-size:clamp(1.6rem,4.5vw,2.6rem);margin:.25rem 0}
.hero p.lead{color:var(--muted);max-width:48rem;margin:0 auto;padding:0 .4rem}
.hero img{max-width:820px;box-shadow:var(--sh)}

/* ---------- SECTIONS ---------- */
.section{padding:1.1rem 0}
.narrow{max-width:820px;margin:0 auto}
.grid3{display:grid;grid-template-columns:1fr;gap:1rem}
.card{border:1px solid var(--line);border-radius:var(--r);background:#fff;padding:1rem;box-shadow:var(--sh)}
h1{margin:.2rem 0 .4rem}
h2{font-size:clamp(1.1rem,3.6vw,1.6rem);margin:.2rem 0 .35rem}

/* ---------- FEATURE ROWS ---------- */
.feature{
  display:grid;grid-template-columns:120px 1fr;gap:.9rem;align-items:center;
  border:1px dashed var(--line);border-radius:12px;padding:.9rem
}
.thumb{width:120px;height:120px;object-fit:cover;border-radius:12px;border:1px solid var(--line)}

/* ---------- TIMELINE ---------- */
.timeline{list-style:none;margin:.6rem 0 0;padding:0}
.timeline li{position:relative;padding-left:1.25rem;margin:.45rem 0}
.timeline li::before{
  content:"";position:absolute;left:.25rem;top:.58rem;width:.5rem;height:.5rem;border-radius:999px;background:var(--brand)
}

/* ---------- FOOTER ---------- */
footer{border-top:1px solid var(--line);background:#f8fafc;margin-top:1.2rem}
.footer{width:min(1140px,94%);margin:0 auto;padding:1.1rem 0;display:grid;gap:1rem}
.fgrid{display:grid;grid-template-columns:1fr;gap:1rem}
.fcol .small{color:var(--muted)}
.fcol a{color:var(--ink)} .fcol a:hover{color:var(--brand-ink)}

/* ---------- FORM (mobile-first) ---------- */
button,input,textarea,select{font:inherit}
.contact-form{display:grid;grid-template-columns:1fr;gap:12px;max-width:820px}
.contact-form .row-2{display:grid;grid-template-columns:1fr 1fr;gap:12px}
.contact-form input,.contact-form textarea{
  width:100%;padding:.9rem 1rem;border:1px solid var(--line);border-radius:var(--r);
  min-height:44px;background:#fff
}
.contact-form textarea{resize:vertical}
.contact-form button{
  width:auto;justify-self:start;padding:.95rem 1.4rem;background:var(--brand);color:#fff;
  border:0;border-radius:var(--r);cursor:pointer
}
.contact-form button:hover{background:var(--brand-ink)}

/* ---------- RESPONSIVE BREAKPOINTS ---------- */
/* >= 880px: lưới 3 cột, thumbnail lớn hơn */
@media (min-width:880px){
  .grid3{grid-template-columns:repeat(3,1fr)}
  .feature{grid-template-columns:140px 1fr}
  .thumb{width:140px;height:140px}
  .hero .wrap{padding:1.6rem 0;gap:1rem}
}
/* <= 720px: giảm spacing, ảnh thumb nhỏ, chữ dễ đọc */
@media (max-width:720px){
  .feature{grid-template-columns:1fr}
  .thumb{width:96px;height:96px;justify-self:center}
  .card{padding:.85rem}
  .section{padding:.9rem 0}
  .nav{justify-content:center}
}
/* <= 640px: form 1 cột */
@media (max-width:640px){
  .contact-form .row-2{grid-template-columns:1fr}
  .hero img{border-radius:12px}
}