:root {
  --bg: #ffffff;
  --surface: #f8fafc;
  --bd: #e2e8f0;
  --text: #0f172a;
  --muted: #64748b;
  --accent: #10b981;
  --accent-2: #7c3aed;
  --gradient: linear-gradient(135deg, #10b981 0%, #7c3aed 100%);
}
* { box-sizing: border-box; }
html, body { margin: 0; padding: 0; }
body { font-family: -apple-system, BlinkMacSystemFont, "Inter", "Segoe UI", system-ui, sans-serif;
  color: var(--text); background: var(--bg); line-height: 1.6; }
a { color: var(--accent-2); text-decoration: none; }
a:hover { text-decoration: underline; }

/* ====== NAV ====== */
nav.top {
  position: sticky; top: 0; z-index: 50;
  background: rgba(255,255,255,.95); backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--bd);
  display: flex; align-items: center; padding: 14px 32px; gap: 24px;
}
nav.top .brand { font-weight: 800; font-size: 20px; display: flex; align-items: center; gap: 8px; }
nav.top .brand .dot { width: 32px; height: 32px; border-radius: 8px; background: var(--gradient); display: inline-block; }
nav.top .links { display: flex; gap: 24px; flex: 1; margin-left: 32px; }
nav.top .links a { color: var(--muted); font-weight: 500; }
nav.top .links a:hover { color: var(--text); text-decoration: none; }
nav.top .cta { padding: 10px 20px; background: var(--text); color: #fff; border-radius: 8px;
  font-weight: 600; font-size: 14px; transition: opacity .15s; }
nav.top .cta:hover { opacity: .85; text-decoration: none; }

/* ====== HERO ====== */
section.hero { padding: 90px 32px 70px; text-align: center; max-width: 980px; margin: 0 auto; }
.hero h1 { font-size: 56px; font-weight: 800; line-height: 1.1; letter-spacing: -1px; margin: 0 0 20px;
  background: var(--gradient); -webkit-background-clip: text; -webkit-text-fill-color: transparent; }
.hero .tag { font-size: 20px; color: var(--muted); max-width: 720px; margin: 0 auto 32px; }
.hero .ctas { display: flex; gap: 12px; justify-content: center; flex-wrap: wrap; margin-bottom: 32px; }
.hero .ctas .btn-primary { padding: 14px 28px; background: var(--text); color: #fff; border-radius: 10px;
  font-weight: 600; font-size: 16px; border: 0; cursor: pointer; }
.hero .ctas .btn-secondary { padding: 14px 28px; background: transparent; color: var(--text); border-radius: 10px;
  font-weight: 600; font-size: 16px; border: 2px solid var(--bd); cursor: pointer; }
.hero .ctas a:hover { text-decoration: none; }
.hero .trust { font-size: 13px; color: var(--muted); }

/* ====== FEATURES ====== */
section.features { padding: 70px 32px; background: var(--surface); }
.features-inner { max-width: 1180px; margin: 0 auto; }
.features h2 { font-size: 36px; text-align: center; margin: 0 0 60px; font-weight: 800; letter-spacing: -.5px; }
.feat-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(280px, 1fr)); gap: 28px; }
.feat-card { background: #fff; border: 1px solid var(--bd); border-radius: 14px; padding: 28px 24px;
  transition: transform .15s, box-shadow .15s; }
.feat-card:hover { transform: translateY(-4px); box-shadow: 0 12px 36px rgba(0,0,0,.08); }
.feat-card .icon { width: 48px; height: 48px; border-radius: 10px;
  background: linear-gradient(135deg, rgba(16,185,129,.15), rgba(124,58,237,.15));
  display: flex; align-items: center; justify-content: center; font-size: 24px;
  margin-bottom: 18px; }
.feat-card h3 { margin: 0 0 8px; font-size: 18px; font-weight: 700; }
.feat-card p { margin: 0; color: var(--muted); font-size: 14px; }

/* ====== PRICING ====== */
section.pricing { padding: 90px 32px; }
.pricing-inner { max-width: 1180px; margin: 0 auto; }
.pricing h2 { font-size: 36px; text-align: center; margin: 0 0 12px; font-weight: 800; }
.pricing .sub { text-align: center; color: var(--muted); margin-bottom: 50px; font-size: 16px; }
.tier-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(240px, 1fr)); gap: 18px; }
.tier { background: #fff; border: 1px solid var(--bd); border-radius: 14px; padding: 32px 24px;
  display: flex; flex-direction: column; }
.tier.featured { border: 2px solid var(--accent-2); transform: scale(1.02); position: relative; }
.tier.featured::before { content: "PHỔ BIẾN NHẤT"; position: absolute; top: -12px; left: 50%; transform: translateX(-50%);
  background: var(--accent-2); color: #fff; font-size: 11px; padding: 4px 12px; border-radius: 12px; font-weight: 700; letter-spacing: .5px; }
.tier h3 { margin: 0 0 6px; font-size: 22px; font-weight: 800; }
.tier .price { font-size: 36px; font-weight: 900; margin: 8px 0; }
.tier .price small { font-size: 14px; font-weight: 500; color: var(--muted); }
.tier .desc { color: var(--muted); font-size: 14px; min-height: 42px; margin-bottom: 18px; }
.tier ul { list-style: none; padding: 0; margin: 0 0 24px; font-size: 14px; flex: 1; }
.tier ul li { padding: 6px 0; display: flex; align-items: flex-start; gap: 8px; }
.tier ul li::before { content: "✓"; color: var(--accent); font-weight: 800; }
.tier button { padding: 12px 20px; background: var(--text); color: #fff; border: 0; border-radius: 10px;
  font-weight: 600; cursor: pointer; font-size: 14px; transition: opacity .15s; }
.tier.featured button { background: var(--accent-2); }
.tier button:hover { opacity: .85; }

/* ====== SIGNUP ====== */
section.signup { padding: 80px 32px; background: var(--gradient); color: #fff; }
.signup-inner { max-width: 560px; margin: 0 auto; text-align: center; }
.signup h2 { font-size: 36px; margin: 0 0 14px; font-weight: 800; }
.signup .tag { font-size: 18px; opacity: .9; margin-bottom: 32px; }
.signup-form { background: #fff; padding: 32px; border-radius: 16px; color: var(--text); text-align: left;
  box-shadow: 0 24px 60px rgba(0,0,0,.2); }
.signup-form label { display: block; font-size: 13px; font-weight: 600; margin: 12px 0 4px; }
.signup-form label:first-child { margin-top: 0; }
.signup-form input, .signup-form select { width: 100%; padding: 11px 14px; border: 1px solid var(--bd); border-radius: 8px;
  font-size: 14px; box-sizing: border-box; }
.signup-form input:focus, .signup-form select:focus { outline: 2px solid var(--accent-2); border-color: var(--accent-2); }
.signup-form .row-2 { display: grid; grid-template-columns: 1fr 1fr; gap: 10px; }
.signup-form .submit { width: 100%; margin-top: 16px; padding: 14px; background: var(--text); color: #fff;
  border: 0; border-radius: 10px; font-weight: 700; font-size: 15px; cursor: pointer; }
.signup-form .submit:disabled { opacity: .5; cursor: not-allowed; }
.signup-form .submit:hover:not(:disabled) { opacity: .9; }
.signup-form .small { font-size: 12px; color: var(--muted); margin-top: 12px; text-align: center; }
.signup-form .err { background: rgba(239,68,68,.1); color: #b91c1c; padding: 10px 14px; border-radius: 8px;
  font-size: 13px; margin-top: 10px; }
.signup-success { background: #f0fdf4; border: 2px solid var(--accent); color: #065f46;
  padding: 24px; border-radius: 12px; text-align: center; }
.signup-success h3 { margin: 0 0 8px; font-size: 22px; }

/* ====== FOOTER ====== */
footer.bottom { padding: 40px 32px; text-align: center; color: var(--muted); font-size: 13px;
  border-top: 1px solid var(--bd); }

@media (max-width: 720px) {
  .hero h1 { font-size: 36px; }
  .hero .tag { font-size: 16px; }
  nav.top .links { display: none; }
  section.hero, section.features, section.pricing, section.signup { padding: 50px 20px; }
  .pricing h2, .features h2, .signup h2 { font-size: 28px; }
}

/* ====== LANGUAGE SWITCHER ====== */
.lang-switch { margin-left: auto; }
.lang-switch select { padding: 6px 10px; border: 1px solid var(--bd); border-radius: 8px;
  font-size: 13px; background: #fff; cursor: pointer; }
nav.top .links + .lang-switch { margin-left: 16px; }

@media (max-width: 720px) {
  .lang-switch { margin-left: 0; }
  .lang-switch select { font-size: 12px; padding: 4px 8px; }
}