/* ============================================================
   Siêu Bất Ngờ — Landing page styles
   Modern, responsive, light/dark. No external CSS framework.
   ============================================================ */

:root {
  --bg: #ffffff;
  --bg-soft: #f6f7fb;
  --bg-card: #ffffff;
  --border: #e7e8f0;
  --text: #11131a;
  --text-soft: #4a4f60;
  --text-muted: #6b7180;
  --brand: #6d5efc;
  --brand-2: #a855f7;
  --brand-3: #ec4899;
  --accent: #f59e0b;
  --ok: #10b981;
  --ring: rgba(109, 94, 252, .35);
  --shadow: 0 10px 30px rgba(17, 19, 26, .08);
  --shadow-lg: 0 24px 60px rgba(70, 50, 180, .18);
  --radius: 18px;
  --maxw: 1140px;
  --font-head: "Be Vietnam Pro", system-ui, sans-serif;
  --font-body: "Inter", "Be Vietnam Pro", system-ui, sans-serif;
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #0b0c12;
    --bg-soft: #11131c;
    --bg-card: #151726;
    --border: #262a3d;
    --text: #f2f3f8;
    --text-soft: #c4c8d8;
    --text-muted: #9298ac;
    --shadow: 0 10px 30px rgba(0, 0, 0, .4);
    --shadow-lg: 0 24px 60px rgba(0, 0, 0, .5);
    --ring: rgba(168, 85, 247, .45);
  }
}
:root[data-theme="dark"] {
  --bg: #0b0c12;
  --bg-soft: #11131c;
  --bg-card: #151726;
  --border: #262a3d;
  --text: #f2f3f8;
  --text-soft: #c4c8d8;
  --text-muted: #9298ac;
  --shadow: 0 10px 30px rgba(0, 0, 0, .4);
  --shadow-lg: 0 24px 60px rgba(0, 0, 0, .5);
  --ring: rgba(168, 85, 247, .45);
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; -webkit-text-size-adjust: 100%; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: var(--font-body);
  font-size: 17px;
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
  overflow-x: hidden;
}
h1, h2, h3, h4 { font-family: var(--font-head); line-height: 1.15; margin: 0 0 .5em; letter-spacing: -.02em; }
p { margin: 0 0 1em; color: var(--text-soft); }
a { color: inherit; text-decoration: none; }
img, svg { max-width: 100%; display: block; }
.container { width: 100%; max-width: var(--maxw); margin: 0 auto; padding: 0 20px; }
.gradient-text {
  background: linear-gradient(100deg, var(--brand), var(--brand-2) 55%, var(--brand-3));
  -webkit-background-clip: text; background-clip: text; color: transparent;
}

/* ---------- i18n visibility ---------- */
[data-lang-en] { display: none; }
html[lang="en"] [data-lang-vi] { display: none; }
html[lang="en"] [data-lang-en] { display: revert; }

/* ---------- buttons ---------- */
.btn {
  display: inline-flex; align-items: center; gap: .55em;
  font-family: var(--font-head); font-weight: 600; font-size: .98rem;
  padding: .85em 1.5em; border-radius: 999px; border: 1px solid transparent;
  cursor: pointer; transition: transform .15s ease, box-shadow .2s ease, background .2s ease;
  white-space: nowrap;
}
.btn:active { transform: translateY(1px); }
.btn-primary {
  color: #fff; background: linear-gradient(100deg, var(--brand), var(--brand-2));
  box-shadow: 0 8px 22px var(--ring);
}
.btn-primary:hover { transform: translateY(-2px); box-shadow: 0 14px 30px var(--ring); }
.btn-ghost { background: var(--bg-card); color: var(--text); border-color: var(--border); }
.btn-ghost:hover { border-color: var(--brand); color: var(--brand); }
.btn-lg { padding: 1.05em 1.9em; font-size: 1.05rem; }

/* ---------- header ---------- */
.site-header {
  position: sticky; top: 0; z-index: 50;
  backdrop-filter: saturate(180%) blur(12px);
  background: color-mix(in srgb, var(--bg) 82%, transparent);
  border-bottom: 1px solid transparent;
  transition: border-color .2s ease, background .2s ease;
}
.site-header.scrolled { border-bottom-color: var(--border); }
.nav { display: flex; align-items: center; justify-content: space-between; height: 70px; }
.brand { display: inline-flex; align-items: center; gap: .6em; font-family: var(--font-head); font-weight: 800; font-size: 1.15rem; letter-spacing: -.02em; }
.brand .logo { width: 34px; height: 34px; border-radius: 10px; box-shadow: var(--shadow); }
.nav-links { display: flex; align-items: center; gap: 28px; list-style: none; margin: 0; padding: 0; }
.nav-links a { color: var(--text-soft); font-weight: 500; font-size: .96rem; transition: color .15s ease; }
.nav-links a:hover { color: var(--brand); }
.nav-right { display: flex; align-items: center; gap: 12px; }
.icon-btn {
  display: inline-grid; place-items: center; width: 40px; height: 40px;
  border-radius: 10px; border: 1px solid var(--border); background: var(--bg-card);
  color: var(--text-soft); cursor: pointer; font-weight: 600; font-size: .85rem;
  transition: border-color .15s, color .15s;
}
.icon-btn:hover { border-color: var(--brand); color: var(--brand); }
.lang-toggle { min-width: 58px; font-family: var(--font-head); }
.menu-btn { display: none; }

/* ---------- hero ---------- */
.hero { position: relative; padding: 76px 0 64px; overflow: hidden; }
.hero::before {
  content: ""; position: absolute; inset: -20% -10% auto -10%; height: 620px; z-index: -1;
  background:
    radial-gradient(60% 55% at 18% 12%, rgba(109, 94, 252, .28), transparent 60%),
    radial-gradient(55% 55% at 85% 8%, rgba(236, 72, 153, .22), transparent 60%),
    radial-gradient(50% 50% at 60% 40%, rgba(168, 85, 247, .18), transparent 60%);
  filter: blur(8px);
}
.hero-grid { display: grid; grid-template-columns: 1.05fr .95fr; gap: 52px; align-items: center; }
.badge {
  display: inline-flex; align-items: center; gap: .5em; font-size: .82rem; font-weight: 600;
  padding: .45em .9em; border-radius: 999px; border: 1px solid var(--border);
  background: var(--bg-card); color: var(--text-soft); margin-bottom: 22px;
  box-shadow: var(--shadow);
}
.badge .dot { width: 8px; height: 8px; border-radius: 50%; background: var(--ok); box-shadow: 0 0 0 4px color-mix(in srgb, var(--ok) 25%, transparent); }
.hero h1 { font-size: clamp(2.1rem, 5vw, 3.5rem); font-weight: 800; }
.hero .lede { font-size: clamp(1.05rem, 2vw, 1.22rem); color: var(--text-soft); max-width: 34ch; }
.hero-cta { display: flex; flex-wrap: wrap; gap: 14px; margin-top: 30px; }
.hero-trust { display: flex; flex-wrap: wrap; gap: 22px; margin-top: 30px; color: var(--text-muted); font-size: .9rem; }
.hero-trust b { color: var(--text); font-family: var(--font-head); }

/* hero visual: chat + json eval */
.hero-visual { position: relative; }
.card {
  background: var(--bg-card); border: 1px solid var(--border);
  border-radius: var(--radius); box-shadow: var(--shadow-lg);
}
.chat-card { padding: 20px; }
.chat-head { display: flex; align-items: center; gap: 10px; padding-bottom: 14px; border-bottom: 1px solid var(--border); margin-bottom: 16px; }
.chat-head .av { width: 36px; height: 36px; border-radius: 50%; background: linear-gradient(135deg, var(--brand), var(--brand-3)); display: grid; place-items: center; color: #fff; font-weight: 700; font-family: var(--font-head); }
.chat-head small { color: var(--text-muted); display: block; font-weight: 500; }
.chat-head strong { font-family: var(--font-head); }
.bubble { max-width: 85%; padding: 11px 14px; border-radius: 14px; font-size: .95rem; margin-bottom: 12px; line-height: 1.5; }
.bubble.them { background: var(--bg-soft); border: 1px solid var(--border); border-top-left-radius: 4px; }
.bubble.me { background: linear-gradient(100deg, var(--brand), var(--brand-2)); color: #fff; margin-left: auto; border-top-right-radius: 4px; }
.eval-card { position: absolute; right: -14px; bottom: -28px; width: 70%; padding: 16px; font-size: .8rem; }
.eval-card .eval-title { display: flex; align-items: center; gap: 8px; font-family: var(--font-head); font-weight: 700; font-size: .85rem; margin-bottom: 10px; }
.eval-card .tag { font-size: .68rem; font-weight: 700; padding: .2em .6em; border-radius: 999px; background: color-mix(in srgb, var(--brand) 14%, transparent); color: var(--brand); }
pre.json { margin: 0; font-family: ui-monospace, "SFMono-Regular", Menlo, monospace; font-size: .76rem; line-height: 1.55; color: var(--text-soft); white-space: pre-wrap; }
.json .k { color: var(--brand-2); }
.json .s { color: var(--ok); }
.json .n { color: var(--accent); }

/* ---------- sections ---------- */
section { padding: 72px 0; }
.section-head { max-width: 720px; margin: 0 auto 48px; text-align: center; }
.eyebrow { font-family: var(--font-head); font-weight: 700; font-size: .8rem; letter-spacing: .12em; text-transform: uppercase; color: var(--brand); margin-bottom: 12px; }
.section-head h2 { font-size: clamp(1.7rem, 3.6vw, 2.5rem); font-weight: 800; }
.section-head p { font-size: 1.08rem; }
.bg-soft { background: var(--bg-soft); }

/* problem stats */
.stats { display: grid; grid-template-columns: repeat(3, 1fr); gap: 22px; }
.stat { background: var(--bg-card); border: 1px solid var(--border); border-radius: var(--radius); padding: 28px; box-shadow: var(--shadow); text-align: center; }
.stat .num { font-family: var(--font-head); font-weight: 800; font-size: 2.4rem; line-height: 1; margin-bottom: 8px; }
.stat p { margin: 0; font-size: .98rem; }

/* agents */
.agents { display: grid; grid-template-columns: 1fr 1fr; gap: 26px; }
.agent-card { position: relative; padding: 32px; border-radius: 22px; border: 1px solid var(--border); background: var(--bg-card); box-shadow: var(--shadow); overflow: hidden; }
.agent-card::after { content: ""; position: absolute; inset: 0 0 auto 0; height: 4px; background: linear-gradient(90deg, var(--brand), var(--brand-3)); }
.agent-card .ic { width: 52px; height: 52px; border-radius: 14px; display: grid; place-items: center; background: color-mix(in srgb, var(--brand) 12%, transparent); color: var(--brand); margin-bottom: 18px; }
.agent-card h3 { font-size: 1.3rem; }
.agent-card ul { margin: 16px 0 0; padding-left: 0; list-style: none; }
.agent-card li { position: relative; padding-left: 28px; margin-bottom: 10px; font-size: .96rem; color: var(--text-soft); }
.agent-card li::before { content: "✓"; position: absolute; left: 0; top: 0; color: var(--ok); font-weight: 800; }

/* features grid */
.features { display: grid; grid-template-columns: repeat(3, 1fr); gap: 22px; }
.feature { padding: 28px; border-radius: var(--radius); border: 1px solid var(--border); background: var(--bg-card); box-shadow: var(--shadow); transition: transform .18s ease, box-shadow .2s ease; }
.feature:hover { transform: translateY(-4px); box-shadow: var(--shadow-lg); }
.feature .ic { font-size: 1.7rem; margin-bottom: 14px; }
.feature h3 { font-size: 1.12rem; }
.feature p { margin: 0; font-size: .95rem; }

/* how it works */
.steps { display: grid; grid-template-columns: repeat(4, 1fr); gap: 20px; counter-reset: step; }
.step { position: relative; padding: 26px 22px; border-radius: var(--radius); background: var(--bg-card); border: 1px solid var(--border); box-shadow: var(--shadow); }
.step .n { counter-increment: step; font-family: var(--font-head); font-weight: 800; font-size: 1rem; width: 38px; height: 38px; border-radius: 50%; display: grid; place-items: center; color: #fff; background: linear-gradient(135deg, var(--brand), var(--brand-2)); margin-bottom: 16px; }
.step .n::before { content: counter(step); }
.step h3 { font-size: 1.05rem; }
.step p { margin: 0; font-size: .92rem; }

/* why claude */
.claude-wrap { display: grid; grid-template-columns: .9fr 1.1fr; gap: 44px; align-items: center; }
.claude-card { padding: 34px; border-radius: 22px; background: linear-gradient(145deg, color-mix(in srgb, var(--brand) 12%, var(--bg-card)), var(--bg-card)); border: 1px solid var(--border); box-shadow: var(--shadow-lg); }
.ask-list { list-style: none; margin: 0; padding: 0; display: grid; gap: 16px; }
.ask-list li { display: flex; gap: 14px; align-items: flex-start; }
.ask-list .ic { flex: none; width: 42px; height: 42px; border-radius: 12px; display: grid; place-items: center; background: color-mix(in srgb, var(--brand) 14%, transparent); color: var(--brand); font-weight: 700; }
.ask-list h4 { font-size: 1.02rem; margin: 0 0 3px; }
.ask-list p { margin: 0; font-size: .92rem; }

/* cta band */
.cta-band { position: relative; padding: 0; }
.cta-inner { position: relative; overflow: hidden; border-radius: 28px; padding: 60px 40px; text-align: center; color: #fff; background: linear-gradient(120deg, #5b4bf0, #8b43e6 55%, #d6409f); box-shadow: var(--shadow-lg); }
.cta-inner::before { content: ""; position: absolute; inset: 0; background: radial-gradient(60% 120% at 80% 0%, rgba(255,255,255,.22), transparent 60%); }
.cta-inner h2 { color: #fff; font-size: clamp(1.7rem, 4vw, 2.6rem); position: relative; }
.cta-inner p { color: rgba(255,255,255,.9); max-width: 48ch; margin: 0 auto 28px; position: relative; }
.cta-inner .btn-primary { background: #fff; color: var(--brand); box-shadow: 0 10px 30px rgba(0,0,0,.2); position: relative; }
.cta-inner .btn-ghost { background: transparent; color: #fff; border-color: rgba(255,255,255,.5); position: relative; }
.cta-inner .btn-ghost:hover { border-color: #fff; color: #fff; }
.cta-note { margin-top: 18px; font-size: .86rem; color: rgba(255,255,255,.8); position: relative; }

/* footer */
.site-footer { padding: 54px 0 34px; border-top: 1px solid var(--border); background: var(--bg-soft); }
.footer-grid { display: flex; flex-wrap: wrap; justify-content: space-between; gap: 30px; margin-bottom: 30px; }
.footer-grid .about { max-width: 320px; }
.footer-col h5 { font-family: var(--font-head); font-size: .9rem; margin: 0 0 14px; }
.footer-col ul { list-style: none; margin: 0; padding: 0; }
.footer-col li { margin-bottom: 9px; }
.footer-col a { color: var(--text-muted); font-size: .92rem; }
.footer-col a:hover { color: var(--brand); }
.footer-bottom { display: flex; flex-wrap: wrap; justify-content: space-between; gap: 12px; padding-top: 22px; border-top: 1px solid var(--border); color: var(--text-muted); font-size: .86rem; }

/* reveal on scroll */
.reveal { opacity: 0; transform: translateY(22px); transition: opacity .6s ease, transform .6s ease; }
.reveal.in { opacity: 1; transform: none; }
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  .reveal { opacity: 1; transform: none; transition: none; }
}

/* ---------- responsive ---------- */
@media (max-width: 920px) {
  .hero-grid, .claude-wrap { grid-template-columns: 1fr; }
  .hero-visual { margin-top: 20px; }
  .agents { grid-template-columns: 1fr; }
  .features, .steps, .stats { grid-template-columns: 1fr 1fr; }
}
@media (max-width: 680px) {
  body { font-size: 16px; }
  .nav-links { display: none; }
  .menu-btn { display: inline-grid; }
  .features, .steps, .stats { grid-template-columns: 1fr; }
  .eval-card { position: static; width: 100%; margin-top: 16px; }
  .hero-visual .card.chat-card { box-shadow: var(--shadow); }
  section { padding: 56px 0; }
  .cta-inner { padding: 44px 22px; }
}