/* Khai.AI — CSS chung cho trang giới thiệu tĩnh. */
:root {
  --ink: #0f172a;
  --ink-2: #334155;
  --muted: #64748b;
  --line: #e2e8f0;
  --paper: #f8fafc;
  --brand: #4338ca;
  --brand-2: #372fa8;
  --cyan: #0ea5e9;
  --tint: #eef2ff;
  --ok: #15803d;
  --radius: 14px;
  --shadow: 0 12px 40px rgba(15, 23, 42, .08);
  --max: 1120px;
}
* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  font-family: Mulish, ui-sans-serif, system-ui, sans-serif;
  color: var(--ink);
  background: #fff;
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
}
img { max-width: 100%; display: block; }
a { color: var(--brand); }
:focus-visible { outline: 2px solid var(--cyan); outline-offset: 3px; }

.skip {
  position: absolute; left: 12px; top: -48px;
  background: var(--brand); color: #fff; padding: 8px 12px; border-radius: 8px; z-index: 40;
  text-decoration: none; font-weight: 700;
}
.skip:focus { top: 12px; }

.wrap { width: min(var(--max), calc(100% - 40px)); margin: 0 auto; }

.nav {
  position: sticky; top: 0; z-index: 30;
  background: rgba(255,255,255,.92);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--line);
}
.nav__in {
  width: min(var(--max), calc(100% - 40px));
  margin: 0 auto;
  min-height: 64px;
  display: flex; align-items: center; gap: 18px;
}
.brand {
  display: flex; align-items: center; gap: 10px;
  text-decoration: none; color: inherit;
  font-weight: 800; font-size: 1.15rem; letter-spacing: -.02em;
}
.brand img { width: 32px; height: 32px; }
.brand .ai { color: var(--cyan); }
.nav__links { display: flex; gap: 22px; margin-left: 8px; }
.nav__links a { color: var(--ink-2); text-decoration: none; font-weight: 600; font-size: .95rem; }
.nav__links a:hover { color: var(--brand); }
.nav__spacer { margin-left: auto; }
.nav-more { display: none; margin-left: auto; position: relative; }
.nav-more summary {
  list-style: none; cursor: pointer; font-weight: 700; color: var(--ink-2);
  padding: 8px 10px; border: 1px solid var(--line); border-radius: 10px;
}
.nav-more summary::-webkit-details-marker { display: none; }
.nav-more__panel {
  position: absolute; right: 0; top: 48px;
  background: #fff; border: 1px solid var(--line); border-radius: 12px;
  padding: 12px; min-width: 220px; box-shadow: var(--shadow);
  display: flex; flex-direction: column; gap: 4px;
}
.nav-more__panel a { text-decoration: none; color: var(--ink); font-weight: 600; padding: 8px 10px; border-radius: 8px; }
.nav-more__panel a:hover { background: var(--tint); }

.btn {
  display: inline-flex; align-items: center; justify-content: center;
  height: 44px; padding: 0 18px; border-radius: 11px;
  font-weight: 800; font-size: .95rem; text-decoration: none;
  border: 1px solid transparent;
}
.btn--primary { background: var(--brand); color: #fff; }
.btn--primary:hover { background: var(--brand-2); }
.btn--ghost { background: #fff; color: var(--ink); border-color: var(--line); }
.btn--ghost:hover { border-color: #c7d2fe; }
.btn--light { background: #fff; color: var(--brand); }
.btn-row, .btn-row { display: flex; flex-wrap: wrap; gap: 10px; }

.hero {
  overflow: hidden;
  background:
    radial-gradient(900px 420px at 85% -10%, rgba(14,165,233,.16), transparent 55%),
    radial-gradient(700px 380px at -10% 110%, rgba(67,56,202,.12), transparent 50%),
    var(--paper);
  border-bottom: 1px solid var(--line);
}
.hero__in {
  width: min(var(--max), calc(100% - 40px));
  margin: 0 auto;
  padding: 72px 0 80px;
  display: grid; grid-template-columns: 1.15fr .85fr; gap: 48px; align-items: center;
}
.eyebrow {
  display: inline-block;
  font-size: .72rem; font-weight: 800; letter-spacing: .16em; text-transform: uppercase;
  color: var(--brand); margin: 0 0 14px;
}
.hero h1 {
  margin: 0 0 16px;
  font-size: clamp(2rem, 4.4vw, 3.05rem);
  line-height: 1.15; letter-spacing: -.03em;
}
.lede { font-size: 1.15rem; color: var(--ink-2); max-width: 40rem; margin: 0 0 28px; }
.note { font-size: .9rem; color: var(--muted); margin: 14px 0 0; }

.stack-cards, .stack-cards { display: grid; gap: 0; }
.qcard {
  background: #fff; border: 1px solid var(--line); border-radius: 16px;
  padding: 18px; box-shadow: var(--shadow);
}
.qcard + .qcard { margin-top: -8px; }
.qcard:nth-child(2) { transform: translateX(16px); }
.qcard:nth-child(3) { transform: translateX(8px); }
.qcard b { display: block; font-size: .95rem; margin: 0; }
.tag {
  font-size: .68rem; font-weight: 800; letter-spacing: .08em; text-transform: uppercase;
  color: var(--cyan); margin-bottom: 8px;
}
.opts { display: grid; gap: 8px; margin-top: 12px; }
.opt {
  border: 1px solid var(--line); border-radius: 10px; padding: 8px 12px;
  font-size: .9rem; color: var(--ink-2);
}
.opt.is-ok { border-color: #bbf7d0; background: #f0fdf4; color: var(--ok); font-weight: 700; }

section { padding: 72px 0; }
.band { background: var(--paper); border-block: 1px solid var(--line); }
h2 {
  margin: 0 0 14px;
  font-size: clamp(1.35rem, 2.4vw, 1.75rem);
  line-height: 1.3; letter-spacing: -.02em;
}
.answer { font-size: 1.05rem; color: var(--ink-2); max-width: 46rem; margin: 0 0 16px; }
.follow { font-size: 1.02rem; color: var(--ink-2); max-width: 46rem; margin: 0 0 22px; }
.article a { font-weight: 700; }
.stamp { font-size: .85rem; color: var(--muted); margin: 0 0 10px; }
.compare { width: 100%; max-width: 46rem; border-collapse: collapse; margin: 8px 0 22px; font-size: .94rem; }
.compare th, .compare td { border: 1px solid var(--line); padding: 10px 12px; text-align: left; vertical-align: top; }
.compare th { background: var(--tint); font-size: .72rem; letter-spacing: .08em; text-transform: uppercase; }
.article h2 { margin-top: 2.35rem; }
.article > h2:first-child { margin-top: 0; }
.grid-3 { display: grid; grid-template-columns: repeat(3, 1fr); gap: 18px; }
.card {
  background: #fff; border: 1px solid var(--line); border-radius: var(--radius);
  padding: 22px; display: flex; flex-direction: column; gap: 10px;
  text-decoration: none; color: inherit;
}
a.card:hover { border-color: #c7d2fe; box-shadow: var(--shadow); }
.num { font-size: .75rem; font-weight: 800; letter-spacing: .14em; text-transform: uppercase; color: var(--cyan); }
.card h3 { margin: 0; font-size: 1.12rem; letter-spacing: -.01em; }
.card p { margin: 0; color: var(--ink-2); flex: 1; }
.more { font-weight: 800; color: var(--brand); font-size: .92rem; }

.points { display: grid; gap: 16px; }
.point {
  display: grid; grid-template-columns: 44px 1fr; gap: 14px; align-items: start;
  background: #fff; border: 1px solid var(--line); border-radius: var(--radius); padding: 18px 20px;
}
.icon {
  width: 44px; height: 44px; border-radius: 12px;
  background: var(--tint); color: var(--brand);
  display: grid; place-items: center;
}
.point h3 { margin: 0 0 6px; font-size: 1.05rem; }
.point p { margin: 0; color: var(--ink-2); }

.faq { display: grid; gap: 10px; max-width: 46rem; }
.faq details {
  background: #fff; border: 1px solid var(--line); border-radius: 12px; padding: 0 16px;
}
.faq summary { cursor: pointer; font-weight: 800; padding: 14px 0; list-style: none; }
.faq summary::-webkit-details-marker { display: none; }
.faq details p { margin: 0 0 16px; color: var(--ink-2); }

.cta {
  background:
    radial-gradient(600px 240px at 90% 0%, rgba(14,165,233,.28), transparent 55%),
    linear-gradient(135deg, #362da2, var(--brand) 55%, #1d4ed8);
  color: #fff;
}
.cta h2 { color: #fff; }
.cta .answer { color: #e0e7ff; }

.page-hero,
.page-hero { padding: 52px 0 8px; }
.crumbs,
.crumbs { font-size: .9rem; color: var(--muted); margin: 0 0 18px; }
.crumbs a,
.crumbs a { color: inherit; }
.eyebrow { margin: 0 0 8px; }
.prose,
.prose { max-width: 46rem; padding-bottom: 64px; }
.prose h2,
.prose h2 { margin-top: 2.4rem; }
.prose p, .prose li,
.prose p, .prose li { color: var(--ink-2); }
.prose ul, .prose ol,
.prose ul { padding-left: 1.2rem; }
.grid-3 { display: grid; grid-template-columns: repeat(3, 1fr); gap: 18px; }
.num { font-size: .75rem; font-weight: 800; letter-spacing: .14em; text-transform: uppercase; color: var(--cyan); }
.more { font-weight: 800; color: var(--brand); font-size: .92rem; }
.skip { position: absolute; left: 12px; top: -48px; background: var(--brand); color: #fff; padding: 8px 12px; border-radius: 8px; z-index: 40; text-decoration: none; font-weight: 700; }
.skip:focus { top: 12px; }
.nav-more { display: none; margin-left: auto; position: relative; }
.nav-more summary {
  list-style: none; cursor: pointer; font-weight: 700; color: var(--ink-2);
  padding: 8px 10px; border: 1px solid var(--line); border-radius: 10px;
}
.nav-more summary::-webkit-details-marker { display: none; }
.nav-more__panel {
  position: absolute; right: 0; top: 48px;
  background: #fff; border: 1px solid var(--line); border-radius: 12px;
  padding: 12px; min-width: 220px; box-shadow: var(--shadow);
  display: flex; flex-direction: column; gap: 4px;
}
.nav-more__panel a { text-decoration: none; color: var(--ink); font-weight: 600; padding: 8px 10px; border-radius: 8px; }

.foot { border-top: 1px solid var(--line); background: #fff; }
.foot__in {
  width: min(var(--max), calc(100% - 40px));
  margin: 0 auto; padding: 28px 0 36px;
  display: flex; flex-wrap: wrap; gap: 12px 24px;
  color: var(--muted); font-size: .9rem; align-items: center;
}
.foot a { color: inherit; }

.byline { font-size: .9rem; color: var(--muted); margin: 0 0 28px; max-width: 46rem; }
.callout {
  background: var(--paper); border: 1px solid var(--line); border-radius: 12px;
  padding: 14px 16px; font-size: .92rem; color: var(--ink-2);
  max-width: 46rem; margin: 0 0 28px;
}
.related { margin-top: 48px; padding-top: 28px; border-top: 1px solid var(--line); max-width: 46rem; }
.related h2 { font-size: 1.2rem; margin-top: 0; }
.related ul { padding-left: 1.2rem; }
.blog-list { display: grid; gap: 16px; max-width: 46rem; padding-bottom: 72px; }
.blog-item {
  display: block; padding: 22px; border: 1px solid var(--line);
  border-radius: var(--radius); text-decoration: none; color: inherit;
}
.blog-item:hover { border-color: #c7d2fe; box-shadow: var(--shadow); }
.blog-item .num { display: block; margin-bottom: 6px; }
.blog-item h2 { margin: 0 0 8px; font-size: 1.25rem; }
.blog-item p { margin: 0; color: var(--ink-2); }
.article ol { max-width: 46rem; }
.article h3 { margin: 1.15rem 0 8px; font-size: 1.08rem; letter-spacing: -.01em; }

.bill {
  display: flex; justify-content: center; gap: 0;
  margin: 0 auto 28px; width: fit-content;
  border: 1px solid var(--line); border-radius: 999px;
  padding: 4px; background: var(--paper);
}
.bill button {
  border: 0; background: transparent; cursor: pointer;
  font-weight: 800; font-family: inherit; font-size: .92rem;
  padding: 10px 18px; border-radius: 999px; color: var(--ink-2);
}
.bill button[aria-pressed="true"] { background: var(--brand); color: #fff; }
.plans {
  display: grid; grid-template-columns: repeat(3, 1fr); gap: 18px;
  align-items: stretch; margin-bottom: 20px;
}
.plan {
  background: #fff; border: 1px solid var(--line);
  border-radius: 16px; padding: 24px 22px;
  display: flex; flex-direction: column; gap: 10px;
  position: relative;
}
.plan--plus {
  border-color: var(--brand);
  box-shadow: var(--shadow);
}
.plan__badge {
  position: absolute; top: -11px; left: 22px;
  background: var(--brand); color: #fff;
  font-size: .68rem; font-weight: 800; letter-spacing: .08em;
  text-transform: uppercase; padding: 4px 10px; border-radius: 999px;
}
.plan__kicker {
  margin: 0; font-size: .72rem; font-weight: 800;
  letter-spacing: .12em; text-transform: uppercase; color: var(--cyan);
}
.plan__name { margin: 0; font-size: 1.45rem; font-weight: 800; letter-spacing: -.02em; }
.plan__num { font-size: 2rem; font-weight: 800; letter-spacing: -.03em; line-height: 1.15; }
.plan__unit { color: var(--muted); font-weight: 600; font-size: .92rem; }
.plan__was { color: var(--muted); text-decoration: line-through; font-size: .9rem; }
.plan__save {
  display: inline-block; margin-top: 6px;
  background: #ecfdf5; color: var(--ok);
  font-size: .78rem; font-weight: 800; padding: 3px 8px; border-radius: 999px;
}
.plan__blurb { margin: 0; color: var(--ink-2); font-size: .95rem; }
.plan ul { margin: 4px 0 8px; padding-left: 1.15rem; color: var(--ink-2); flex: 1; }
.plan li { margin: 5px 0; }
.plan .btn { width: 100%; margin-top: auto; }

@media (max-width: 900px) {
  .hero__in { grid-template-columns: 1fr; padding: 48px 0 56px; }
  .qcard:nth-child(2), .qcard:nth-child(3) { transform: none; }
  .grid-3, .plans { grid-template-columns: 1fr; }
  .plan--plus { transform: none; }
  .nav__links, .nav__in > .btn--ghost { display: none; }
  .nav-more, .nav-more { display: block; }
}
@media (max-width: 640px) {
  .wrap, .hero__in, .nav__in, .foot__in { width: calc(100% - 32px); }
  section { padding: 52px 0; }
  .btn-row .btn { flex: 1; }
}