/* =====================================================================
   Sàn Ứng Dụng AI — trang giới thiệu
   Phong cách: tối giản, tin cậy, doanh nghiệp (tham khảo Stripe, Linear; pattern Tailwind UI)
   Quy tắc: khoảng cách bội số 8px · max-width 1200px · bo góc 8px · bóng nhẹ · mobile-first
   ===================================================================== */
:root {
  --primary: #0F3D6E;
  --primary-hover: #0B2F56;
  --primary-50: #EEF3F9;
  --primary-100: #DCE6F2;
  --accent: #F2A900;
  --accent-hover: #D99800;
  --accent-50: #FEF6E0;
  --bg: #FFFFFF;
  --bg-alt: #F7F8FA;
  --text: #1A1A1A;
  --text-2: #4B5563;
  --text-3: #6B7280;
  --border: #E5E7EB;
  --border-strong: #D1D5DB;
  --ok: #15803D;
  --danger: #B91C1C;

  --font: "Be Vietnam Pro", "Segoe UI", system-ui, -apple-system, Roboto, Arial, sans-serif;
  --radius: 8px;
  --shadow-sm: 0 1px 2px rgba(16, 24, 40, .05);
  --shadow: 0 1px 3px rgba(16, 24, 40, .08), 0 1px 2px rgba(16, 24, 40, .04);
  --shadow-lg: 0 12px 24px -4px rgba(16, 24, 40, .08), 0 4px 8px -2px rgba(16, 24, 40, .04);
  --container: 1200px;

  /* thang khoảng cách 8px */
  --s1: 8px; --s2: 16px; --s3: 24px; --s4: 32px; --s5: 40px; --s6: 48px; --s8: 64px; --s10: 80px; --s12: 96px;
}

/* ---------------------------------------------------------------- nền */
*, *::before, *::after { box-sizing: border-box; }
html { scroll-behavior: smooth; scroll-padding-top: 80px; -webkit-text-size-adjust: 100%; }
body { margin: 0; background: var(--bg); color: var(--text); font: 400 16px/1.6 var(--font); -webkit-font-smoothing: antialiased; }
h1, h2, h3, h4 { margin: 0; color: var(--text); letter-spacing: -.02em; }
p { margin: 0; }
a { color: inherit; text-decoration: none; }
img, svg { display: block; }
.sprite { position: absolute; width: 0; height: 0; overflow: hidden; }
.i { width: 20px; height: 20px; flex: none; fill: none; stroke: currentColor; stroke-width: 1.75; stroke-linecap: round; stroke-linejoin: round; }
.container { width: 100%; max-width: var(--container); margin: 0 auto; padding: 0 var(--s2); }
:focus-visible { outline: 2px solid var(--primary); outline-offset: 2px; border-radius: 4px; }
.skip { position: absolute; left: -9999px; }
.skip:focus { left: var(--s2); top: var(--s2); z-index: 100; background: var(--bg); padding: var(--s1) var(--s2); border-radius: var(--radius); box-shadow: var(--shadow-lg); }
.link { color: var(--primary); font-weight: 500; text-decoration: underline; text-underline-offset: 3px; }
.link:hover { color: var(--primary-hover); }

/* ---------------------------------------------------------------- nút */
.btn {
  display: inline-flex; align-items: center; justify-content: center; gap: var(--s1);
  height: 40px; padding: 0 var(--s2); border-radius: var(--radius); border: 1px solid transparent;
  font: 600 15px/1 var(--font); cursor: pointer; white-space: nowrap;
  transition: background-color .15s, border-color .15s, color .15s, box-shadow .15s, transform .15s;
}
.btn .i { width: 18px; height: 18px; transition: transform .15s; }
.btn:hover .i { transform: translateX(2px); }
.btn-lg { height: 48px; padding: 0 var(--s3); font-size: 16px; }
.btn-block { width: 100%; }
.btn-primary { background: var(--primary); color: #fff; box-shadow: var(--shadow-sm); }
.btn-primary:hover { background: var(--primary-hover); }
.btn-accent { background: var(--accent); color: #1A1A1A; box-shadow: var(--shadow-sm); }
.btn-accent:hover { background: var(--accent-hover); }
.btn-secondary { background: var(--bg); color: var(--text); border-color: var(--border-strong); box-shadow: var(--shadow-sm); }
.btn-secondary:hover { background: var(--bg-alt); border-color: var(--text-3); }
.btn[disabled] { opacity: .7; cursor: wait; }
.spinner { display: none; width: 16px; height: 16px; border-radius: 50%; border: 2px solid currentColor; border-right-color: transparent; animation: spin .7s linear infinite; }
.btn[aria-busy="true"] .spinner { display: inline-block; }
@keyframes spin { to { transform: rotate(360deg); } }

/* ---------------------------------------------------------------- 1. header */
.header { position: sticky; top: 0; z-index: 50; background: rgba(255, 255, 255, .92); backdrop-filter: saturate(1.8) blur(8px); -webkit-backdrop-filter: saturate(1.8) blur(8px); border-bottom: 1px solid transparent; transition: border-color .2s, box-shadow .2s; }
.header.is-scrolled { border-color: var(--border); box-shadow: var(--shadow-sm); }
.header-inner { display: flex; align-items: center; gap: var(--s3); height: 64px; }
.logo { display: inline-flex; align-items: center; gap: 10px; font-weight: 600; font-size: 17px; letter-spacing: -.01em; color: var(--text); }
.logo b { color: var(--primary); font-weight: 700; }
.logo-mark { width: 32px; height: 32px; }
.logo-light, .logo-light b { color: #fff; }
.nav { display: none; }
.header-cta { display: none; }
.menu-btn { margin-left: auto; display: grid; place-items: center; width: 40px; height: 40px; border: 1px solid var(--border); border-radius: var(--radius); background: var(--bg); color: var(--text); cursor: pointer; }
.menu-btn:hover { background: var(--bg-alt); }
/* menu mobile */
.nav.is-open {
  display: flex; flex-direction: column; gap: var(--s1); position: absolute; left: 0; right: 0; top: 64px;
  padding: var(--s2); background: var(--bg); border-bottom: 1px solid var(--border); box-shadow: var(--shadow-lg);
}
.nav a { padding: var(--s1) var(--s1); border-radius: var(--radius); font-weight: 500; color: var(--text-2); }
.nav a:hover { color: var(--text); background: var(--bg-alt); }
.nav .nav-cta-mobile { margin-top: var(--s1); color: #fff; }
.nav .nav-cta-mobile:hover { color: #fff; background: var(--primary-hover); }

/* ---------------------------------------------------------------- 2. hero */
.hero { padding: var(--s6) 0 var(--s8); background: linear-gradient(180deg, var(--bg) 0%, var(--bg-alt) 100%); border-bottom: 1px solid var(--border); overflow: hidden; }
.hero-grid { display: grid; gap: var(--s6); align-items: center; }
.eyebrow { display: inline-flex; align-items: center; gap: var(--s1); font-size: 14px; font-weight: 600; color: var(--primary); margin-bottom: var(--s2); }
.eyebrow::before { content: ""; width: 16px; height: 2px; background: var(--accent); border-radius: 2px; }
.hero h1 { font-size: clamp(32px, 7.5vw, 52px); line-height: 1.12; font-weight: 700; letter-spacing: -.03em; margin-bottom: var(--s3); text-wrap: balance; }
h2 { text-wrap: balance; }
.lead { font-size: 18px; line-height: 1.7; color: var(--text-2); max-width: 560px; }
.hero-cta { display: flex; flex-direction: column; gap: 12px; margin-top: var(--s4); }
.hero-points { list-style: none; margin: var(--s4) 0 0; padding: 0; display: grid; gap: 12px; font-size: 15px; color: var(--text-2); }
.hero-points li { display: flex; align-items: center; gap: 10px; }
.hero-points .i { width: 18px; height: 18px; color: var(--ok); stroke-width: 2.25; }

.hero-visual { position: relative; padding: var(--s2) 0 var(--s4); }
.mock { background: var(--bg); border: 1px solid var(--border); border-radius: 12px; box-shadow: var(--shadow-lg); overflow: hidden; }
.mock-bar { display: flex; align-items: center; gap: 6px; height: 40px; padding: 0 var(--s2); border-bottom: 1px solid var(--border); background: var(--bg-alt); }
.mock-bar span { width: 10px; height: 10px; border-radius: 50%; background: var(--border-strong); }
.mock-bar em { margin-left: var(--s1); font-style: normal; font-size: 13px; color: var(--text-3); white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.mock-body { padding: var(--s3); }
.mock-head { display: flex; align-items: flex-end; justify-content: space-between; margin-bottom: 12px; }
.mock-head small { display: block; font-size: 13px; color: var(--text-3); }
.mock-head strong { font-size: 32px; font-weight: 700; letter-spacing: -.02em; color: var(--primary); font-variant-numeric: tabular-nums; }
.chip { display: inline-flex; align-items: center; height: 24px; padding: 0 10px; border-radius: 999px; font-size: 12px; font-weight: 600; }
.chip-ok { background: #E8F5EC; color: var(--ok); }
.progress { height: 8px; border-radius: 999px; background: var(--primary-50); overflow: hidden; margin-bottom: var(--s3); }
.progress i { display: block; width: 68%; height: 100%; background: var(--primary); border-radius: inherit; }
.mock-steps { list-style: none; margin: 0; padding: 0; display: grid; gap: 4px; }
.mock-steps li { display: grid; grid-template-columns: 20px 1fr auto; gap: 12px; align-items: center; padding: 10px 0; border-top: 1px solid var(--border); font-size: 14px; font-weight: 500; }
.mock-steps li:first-child { border-top: 0; }
.mock-steps em { font-style: normal; font-size: 13px; font-weight: 400; color: var(--text-3); }
.mock-steps span { width: 20px; height: 20px; border-radius: 50%; border: 2px solid var(--border-strong); position: relative; }
.mock-steps .done span { background: var(--primary); border-color: var(--primary); }
.mock-steps .done span::after { content: ""; position: absolute; left: 5px; top: 2px; width: 5px; height: 9px; border: solid #fff; border-width: 0 2px 2px 0; transform: rotate(45deg); }
.mock-steps .run span { border-color: var(--accent); border-right-color: transparent; animation: spin 1.2s linear infinite; }
.mock-steps .run em { color: #9A6A00; font-weight: 500; }
.float-card { position: absolute; display: flex; align-items: center; gap: 12px; padding: 12px var(--s2); background: var(--bg); border: 1px solid var(--border); border-radius: var(--radius); box-shadow: var(--shadow-lg); }
.float-card .i { width: 36px; height: 36px; padding: 8px; border-radius: var(--radius); background: var(--primary-50); color: var(--primary); }
.float-card strong { display: block; font-size: 14px; font-weight: 600; }
.float-card small { display: block; font-size: 13px; color: var(--text-3); }
.float-a { right: -8px; bottom: -8px; }
.float-b { display: none; }

/* ---------------------------------------------------------------- khối chung */
.section { padding: var(--s8) 0; }
.section-alt { background: var(--bg-alt); border-top: 1px solid var(--border); border-bottom: 1px solid var(--border); }
.section-head { max-width: 640px; margin-bottom: var(--s5); }
.section-head-center { margin-left: auto; margin-right: auto; text-align: center; }
.section-head-center .eyebrow { justify-content: center; }
.section-head h2 { font-size: clamp(28px, 5vw, 40px); line-height: 1.2; font-weight: 700; margin-bottom: var(--s2); }
.section-head p { font-size: 17px; color: var(--text-2); }

/* ---------------------------------------------------------------- 3. dịch vụ */
.services { display: grid; gap: var(--s2); }
.service { padding: var(--s3); border: 1px solid var(--border); border-radius: var(--radius); background: var(--bg); transition: border-color .15s, box-shadow .15s, transform .15s; }
.service:hover { border-color: var(--primary-100); box-shadow: var(--shadow-lg); transform: translateY(-2px); }
.service-icon { display: inline-grid; place-items: center; width: 48px; height: 48px; border-radius: var(--radius); background: var(--primary-50); color: var(--primary); margin-bottom: var(--s3); transition: background-color .15s, color .15s; }
.service:hover .service-icon { background: var(--primary); color: #fff; }
.service-icon .i { width: 24px; height: 24px; }
.service h3 { font-size: 18px; font-weight: 600; margin-bottom: var(--s1); }
.service p { font-size: 15px; color: var(--text-2); }

/* ---------------------------------------------------------------- 4. quy trình */
.steps { list-style: none; margin: 0; padding: 0; display: grid; gap: var(--s2); counter-reset: s; }
.step { position: relative; padding: var(--s3); background: var(--bg); border: 1px solid var(--border); border-radius: var(--radius); box-shadow: var(--shadow-sm); }
.step-num { display: inline-block; font-size: 14px; font-weight: 700; color: var(--primary); padding: 4px 10px; border-radius: 6px; background: var(--accent-50); border: 1px solid #F8DE99; margin-bottom: var(--s2); font-variant-numeric: tabular-nums; }
.step h3 { font-size: 18px; font-weight: 600; margin-bottom: var(--s1); }
.step p { font-size: 15px; color: var(--text-2); }

/* ---------------------------------------------------------------- 5. bảng giá */
.plans { display: grid; gap: var(--s3); align-items: stretch; }
.plan { position: relative; display: flex; flex-direction: column; padding: var(--s4); background: var(--bg); border: 1px solid var(--border); border-radius: var(--radius); box-shadow: var(--shadow-sm); transition: box-shadow .15s; }
.plan:hover { box-shadow: var(--shadow-lg); }
.plan h3 { font-size: 18px; font-weight: 600; }
.plan-desc { margin-top: var(--s1); font-size: 15px; color: var(--text-2); min-height: 48px; }
.price { display: flex; flex-wrap: wrap; align-items: baseline; gap: 4px 6px; margin: var(--s3) 0; }
.plans > *, .services > *, .steps > *, .reviews > * { min-width: 0; }
.price strong { font-size: clamp(30px, 8vw, 36px); font-weight: 700; letter-spacing: -.03em; font-variant-numeric: tabular-nums; }
.price span, .price small { font-size: 15px; color: var(--text-3); }
.plan-list { list-style: none; margin: var(--s3) 0 0; padding: var(--s3) 0 0; border-top: 1px solid var(--border); display: grid; gap: 12px; font-size: 15px; }
.plan-list li { display: flex; gap: 12px; align-items: flex-start; }
.plan-list .i { width: 20px; height: 20px; color: var(--primary); stroke-width: 2.25; margin-top: 2px; }
.plan-featured { border: 2px solid var(--primary); box-shadow: var(--shadow-lg); }
.plan-featured .price strong { color: var(--primary); }
.plan-badge { position: absolute; top: -13px; left: var(--s4); height: 26px; padding: 0 12px; display: inline-flex; align-items: center; border-radius: 999px; background: var(--accent); color: #1A1A1A; font-size: 13px; font-weight: 600; }

/* ---------------------------------------------------------------- 6. đánh giá */
.draft-note { display: inline-block; margin-top: var(--s1); padding: 4px 12px; border: 1px dashed var(--border-strong); border-radius: var(--radius); font-size: 14px !important; color: var(--text-3) !important; }
.reviews { display: grid; gap: var(--s3); }
.review { margin: 0; display: flex; flex-direction: column; padding: var(--s4); background: var(--bg); border: 1px solid var(--border); border-radius: var(--radius); box-shadow: var(--shadow-sm); }
.review-quote { width: 28px; height: 28px; color: var(--accent); fill: var(--accent-50); margin-bottom: var(--s2); }
.review blockquote { margin: 0 0 var(--s3); font-size: 16px; line-height: 1.7; color: var(--text-2); flex: 1; }
.review figcaption { display: flex; align-items: center; gap: 12px; padding-top: var(--s2); border-top: 1px solid var(--border); }
.avatar { display: grid; place-items: center; width: 40px; height: 40px; border-radius: 50%; background: var(--primary-50); color: var(--primary); font-weight: 700; }
.review strong { display: block; font-size: 15px; font-weight: 600; }
.review small { display: block; font-size: 14px; color: var(--text-3); }

/* ---------------------------------------------------------------- 7. FAQ */
.faq-grid { display: grid; gap: var(--s4); }
.faq { border-top: 1px solid var(--border); }
.faq details { border-bottom: 1px solid var(--border); }
.faq summary {
  display: flex; justify-content: space-between; align-items: center; gap: var(--s2); padding: 20px 0;
  font-size: 17px; font-weight: 600; cursor: pointer; list-style: none; transition: color .15s;
}
.faq summary::-webkit-details-marker { display: none; }
.faq summary:hover { color: var(--primary); }
.faq summary .i { color: var(--text-3); transition: transform .2s; }
.faq details[open] summary .i { transform: rotate(180deg); color: var(--primary); }
.faq details p { padding: 0 var(--s4) 20px 0; color: var(--text-2); font-size: 16px; }

/* ---------------------------------------------------------------- 8. CTA + form */
.cta { background: var(--primary); color: #DCE6F2; }
.cta-grid { display: grid; gap: var(--s5); }
.cta h2 { color: #fff; font-size: clamp(28px, 5vw, 40px); line-height: 1.2; font-weight: 700; margin-bottom: var(--s2); }
.cta-copy > p { font-size: 17px; line-height: 1.7; }
.eyebrow-light { color: var(--accent); }
.cta-points { list-style: none; padding: 0; margin: var(--s4) 0 0; display: grid; gap: var(--s2); }
.cta-points li { display: flex; align-items: center; gap: 12px; }
.cta-points .i { width: 36px; height: 36px; padding: 8px; border-radius: var(--radius); background: rgba(255, 255, 255, .08); color: var(--accent); }
.cta-points a { color: #fff; text-decoration: underline; text-underline-offset: 3px; }

.form { display: grid; gap: var(--s2); padding: var(--s3); background: var(--bg); color: var(--text); border-radius: var(--radius); box-shadow: 0 24px 48px -12px rgba(0, 0, 0, .35); }
.form-row { display: grid; gap: var(--s2); }
.field { display: grid; gap: 6px; }
.field label { font-size: 14px; font-weight: 500; color: var(--text); }
.field label span { color: var(--danger); }
.field input, .field select, .field textarea {
  width: 100%; min-height: 44px; padding: 10px 12px; border: 1px solid var(--border-strong); border-radius: var(--radius);
  background: var(--bg); color: var(--text); font: 400 15px/1.5 var(--font); box-shadow: var(--shadow-sm);
  transition: border-color .15s, box-shadow .15s;
}
.field textarea { resize: vertical; min-height: 104px; }
.field select { appearance: none; background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='20' height='20' viewBox='0 0 24 24' fill='none' stroke='%236B7280' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpath d='m6 9 6 6 6-6'/%3E%3C/svg%3E"); background-repeat: no-repeat; background-position: right 12px center; padding-right: 40px; }
.field input:hover, .field select:hover, .field textarea:hover { border-color: var(--text-3); }
.field input:focus, .field select:focus, .field textarea:focus { outline: none; border-color: var(--primary); box-shadow: 0 0 0 3px var(--primary-100); }
.field [aria-invalid="true"] { border-color: var(--danger); }
.hp { position: absolute; left: -9999px; width: 1px; height: 1px; overflow: hidden; }
.consent { display: flex; gap: 12px; align-items: flex-start; font-size: 14px; color: var(--text-2); cursor: pointer; }
.consent input { width: 18px; height: 18px; margin: 2px 0 0; accent-color: var(--primary); flex: none; }
.form-msg { font-size: 14px; min-height: 22px; }
.form-msg.ok { color: var(--ok); } .form-msg.err { color: var(--danger); }

/* ---------------------------------------------------------------- 9. footer */
.footer { background: #0A2A4D; color: #A9BBD1; padding: var(--s8) 0 var(--s4); font-size: 15px; }
.footer-grid { display: grid; gap: var(--s5); padding-bottom: var(--s6); }
.footer-brand p { margin-top: var(--s2); max-width: 320px; }
.footer h4 { color: #fff; font-size: 14px; font-weight: 600; margin-bottom: var(--s2); }
.footer-grid > div:not(.footer-brand) { display: grid; gap: 12px; align-content: start; }
.footer a:hover { color: #fff; }
.footer-bottom { display: flex; flex-direction: column; gap: var(--s1); padding-top: var(--s3); border-top: 1px solid rgba(255, 255, 255, .1); font-size: 14px; }
.footer-bottom p:last-child { display: flex; gap: var(--s3); }

/* ================================================================ ≥ 640px */
@media (min-width: 640px) {
  .container { padding: 0 var(--s3); }
  .hero-cta { flex-direction: row; }
  .services, .steps, .reviews { grid-template-columns: repeat(2, 1fr); }
  .form-row { grid-template-columns: 1fr 1fr; }
  .form { padding: var(--s4); }
  .float-b { display: flex; right: 16px; top: -16px; }
  .footer-grid { grid-template-columns: 1fr 1fr; }
  .footer-bottom { flex-direction: row; justify-content: space-between; }
}

/* ================================================================ ≥ 1024px */
@media (min-width: 1024px) {
  .container { padding: 0 var(--s4); }
  .menu-btn { display: none; }
  .nav { display: flex; gap: var(--s1); margin-left: var(--s4); }
  .nav a { padding: var(--s1) 12px; font-size: 15px; }
  .nav .nav-cta-mobile { display: none; }
  .header-cta { display: inline-flex; margin-left: auto; }
  .hero { padding: var(--s12) 0; }
  .hero-grid { grid-template-columns: 1.05fr .95fr; gap: var(--s8); }
  .hero-visual { padding: var(--s4) var(--s3) var(--s4) var(--s4); }
  .float-a { right: 0; bottom: 0; }
  .float-b { right: 0; top: 8px; }
  .section { padding: var(--s12) 0; }
  .section-head { margin-bottom: var(--s8); }
  .services, .reviews, .plans { grid-template-columns: repeat(3, 1fr); }
  .steps { grid-template-columns: repeat(4, 1fr); }
  .plan-featured { transform: translateY(-8px); }
  .faq-grid { grid-template-columns: 1fr 1.4fr; gap: var(--s8); }
  .cta-grid { grid-template-columns: 1fr 1.1fr; gap: var(--s8); align-items: center; }
  .footer-grid { grid-template-columns: 2fr 1fr 1fr 1fr; }
}

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { animation: none !important; transition: none !important; }
  html { scroll-behavior: auto; }
}