:root {
  --primary-1: #2563eb; /* blue */
  --primary-2: #7c3aed; /* purple */
  --muted: #6b7280;
  --surface: #ffffff;
  --radius: 10px;
  --gradient-primary: linear-gradient(135deg, #4a92ea, #7c3aed);
  --shadow-lg: 0 10px 20px rgba(0,0,0,0.15);
}

* {
  box-sizing: border-box;
}

body {
  font-family: ui-sans-serif, system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial;
  line-height: 1.5;
  color: #0f172a;
  margin: 0;
  background: #f8fafc;
}

.container {
  max-width: 1100px;
  margin: 0 auto;
  padding: 1rem;
}

/* Enhanced header with gradient background and improved styling */
.site-header {
  background: linear-gradient(135deg, #ffffff 0%, #f0f4ff 100%);
  border-bottom: 1px solid rgba(37, 99, 235, 0.1);
  box-shadow: 0 4px 20px rgba(37, 99, 235, 0.08);
  position: sticky;
  top: 0;
  z-index: 100;
  transition: all 0.3s ease;
  width: 100%;
}

.header-inner {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  padding: 1rem 0;
  gap: 1rem;
}

.header-logo {
  width: 48px;
  height: 48px;
  margin-right: 0.4rem;
}

@media (max-width: 768px) {
  .site-header {
    position: fixed;
    width: 100%;
    left: 0;
    right: 0;
  }
  body {
    padding-top: 70px;
  }
  .nav {
    width: 100%;
    background: #fff;
  }
}

.brand {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  text-decoration: none;
  color: inherit;
  transition: all 0.3s ease;
}

.brand:hover {
  transform: translateY(-2px);
}

.logo {
  width: 44px;
  height: 44px;
  border-radius: 8px;
  background: linear-gradient(135deg, var(--primary-1), var(--primary-2));
  padding: 6px;
  box-shadow: 0 4px 12px rgba(37, 99, 235, 0.25);
  transition: all 0.3s ease;
}

.logo:hover {
  transform: scale(1.05);
  box-shadow: 0 6px 16px rgba(37, 99, 235, 0.35);
}

.brand-text {
  font-weight: 700;
  font-size: 1.5rem;
  background: linear-gradient(135deg, var(--primary-1), var(--primary-2));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.nav {
  display: flex;
  gap: 1rem;
  align-items: center;
  transition: all 0.3s ease;
  flex-wrap: wrap;
}

.nav a {
  color: var(--muted);
  text-decoration: none;
  padding: 0.6rem 1rem;
  border-radius: 8px;
  transition: all 0.3s ease;
  position: relative;
  font-weight: 500;
}

.nav a:hover {
  color: var(--primary-1);
  background: rgba(37, 99, 235, 0.08);
  transform: translateY(-2px);
}

.nav .cta {
  color: var(--muted);
  text-decoration: none;
}

.nav-toggle {
  display: none;
  background: none;
  border: 0;
  font-size: 1.5rem;
  cursor: pointer;
  transition: transform 0.3s ease;
  color: var(--primary-1);
  padding: 0.5rem;
  z-index: 51;
}

.nav-toggle:hover {
  transform: scale(1.1);
}

/* Improved active nav styling with gradient and shadow */
.nav a.active {
  color: white;
  background: linear-gradient(135deg, var(--primary-1), var(--primary-2));
  font-weight: 600;
  box-shadow: 0 6px 16px rgba(37, 99, 235, 0.35);
  transform: translateY(-2px);
}

.hero {
  position: relative;
  padding: 4rem 0;
  border-bottom: 1px solid #e6eefc;
  overflow-x: hidden;
  text-align: center;
}

.hero-strong {
  background: linear-gradient(135deg, var(--primary-1), var(--primary-2));
  color: white;
}

.hero-inner {
  display: flex;
  gap: 2rem;
  align-items: center;
  flex-direction: column;
  text-align: center;
  padding: 2rem 1rem;
}

.hero-copy {
  flex: 1;
  padding: 2rem;
  line-height: 1.4;
}

.hero-copy h1 {
  color: white;
  margin: 0 0 0.5rem 0;
  font-size: 2.5rem;
  line-height: 1.2;
}

.hero-copy .lead {
  color: rgba(255, 255, 255, 0.9);
  font-size: 1.1rem;
}

.hero-image img {
  max-width: 420px;
  width: 100%;
  border-radius: 12px;
  box-shadow: 0 12px 40px rgba(15, 23, 42, 0.18);
  transition: transform 0.3s ease;
}

.hero-image img:hover {
  transform: scale(1.02);
}

.hero-decor {
  position: absolute;
  right: 0;
  bottom: -20px;
  width: 60%;
  height: 80px;
  background: linear-gradient(90deg, rgba(124, 58, 237, 0.15), rgba(37, 99, 235, 0.12));
  border-top-left-radius: 40px;
  border-top-right-radius: 0;
  pointer-events: none;
}

.lead {
  color: var(--muted);
  max-width: 560px;
}

.btn {
  display: inline-block;
  padding: 0.6rem 1.2rem;
  border-radius: 8px;
  text-decoration: none;
  cursor: pointer;
  transition: all 0.3s ease;
  border: none;
  font-weight: 500;
}

.btn.primary {
  background: linear-gradient(135deg, var(--primary-1), var(--primary-2));
  color: white;
  box-shadow: 0 8px 30px rgba(37, 99, 235, 0.3);
}

.btn.primary:hover {
  transform: translateY(-2px);
  box-shadow: 0 12px 40px rgba(37, 99, 235, 0.4);
}

.btn.outline {
  border: 2px solid var(--primary-1);
  background: white;
  color: var(--primary-1);
}

.btn.outline:hover {
  background: var(--primary-1);
  color: white;
}

.hero-ctas {
  margin-top: 1.5rem;
  display: flex;
  gap: 1rem;
  flex-wrap: wrap;
}

.section {
  padding: 3rem 0;
}

.section h2 {
  font-size: 2rem;
  margin-bottom: 2rem;
  text-align: center;
}

/* Enhanced section title styling with gradient, underline, and animations */
.section-title {
  font-size: 2rem;
  margin-bottom: 3rem;
  text-align: center;
  position: relative;
  display: inline-block;
  width: 100%;
  background: linear-gradient(135deg, var(--primary-1), var(--primary-2));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  font-weight: 700;
  letter-spacing: -0.5px;
}

.section-title::after {
  content: "";
  position: absolute;
  bottom: -12px;
  left: 50%;
  transform: translateX(-50%);
  width: 60px;
  height: 4px;
  background: linear-gradient(90deg, var(--primary-1), var(--primary-2));
  border-radius: 2px;
  box-shadow: 0 4px 12px rgba(37, 99, 235, 0.3);
}

/* Added new why-choose section styling */
.why-choose {
  background: linear-gradient(135deg, rgba(37, 99, 235, 0.05), rgba(124, 58, 237, 0.05));
  border-radius: 16px;
  padding: 3rem;
}

.why-choose-grid {
  display: grid;
  grid-template-columns: repeat(1, 1fr);
  gap: 2rem;
}

.benefit-card {
  background: white;
  padding: 2rem;
  border-radius: 12px;
  text-align: center;
  transition: all 0.3s ease;
  border: 1px solid transparent;
  box-shadow: 0 4px 12px rgba(15, 23, 42, 0.06);
}

.benefit-card:hover {
  transform: translateY(-6px);
  box-shadow: 0 12px 32px rgba(37, 99, 235, 0.15);
  border-color: var(--primary-1);
}

.benefit-icon {
  font-size: 2.5rem;
  color: #0078ff;
  margin-bottom: 1rem;
  transition: transform 0.3s, color 0.3s;
}

.benefit-card:hover .benefit-icon {
  transform: scale(1.15);
  color: #0056cc;
}

.benefit-card h3 {
  color: var(--primary-1);
  margin: 1rem 0 0.75rem 0;
  font-size: 1.25rem;
}

.benefit-card p {
  color: var(--muted);
  font-size: 0.95rem;
  line-height: 1.6;
}

.features-grid {
  display: grid;
  grid-template-columns: repeat(1, 1fr);
  gap: 1.5rem;
}

.card {
  background: white;
  padding: 1.5rem;
  border-radius: 10px;
  box-shadow: 0 6px 18px rgba(15, 23, 42, 0.04);
  text-align: left;
  transition: all 0.3s ease;
  border: 1px solid transparent;
}

.card:hover {
  transform: translateY(-4px);
  box-shadow: 0 12px 32px rgba(15, 23, 42, 0.12);
  border-color: var(--primary-1);
}

.card img {
  width: 100%;
  height: 200px;
  object-fit: contain;
  border-radius: 8px;
  transition: transform 0.3s ease;
}

.card:hover img {
  transform: scale(1.1);
}

.card h3 {
  color: var(--primary-1);
  margin: 1rem 0 0.5rem 0;
}

.card p {
  color: var(--muted);
  font-size: 0.95rem;
}

.arch-inner {
  display: flex;
  gap: 1.5rem;
  align-items: center;
}

.arch-inner img {
  width: 360px;
  border-radius: 8px;
  transition: transform 0.3s ease;
}

.arch-inner img:hover {
  transform: scale(1.02);
}

.pricing-grid {
  display: grid;
  grid-template-columns: repeat(1, 1fr);
  gap: 1.5rem;
}

.plan {
  background: white;
  padding: 1.5rem;
  border-radius: 10px;
  text-align: center;
  transition: all 0.3s ease;
  border: 2px solid #e6eefc;
}

.plan:hover {
  border-color: var(--primary-1);
  box-shadow: 0 12px 32px rgba(15, 23, 42, 0.12);
}

.plan.featured {
  border: 2px solid var(--primary-1);
  background: linear-gradient(135deg, rgba(37, 99, 235, 0.05), rgba(124, 58, 237, 0.05));
}

.price {
  font-weight: 700;
  font-size: 1.5rem;
  color: var(--primary-1);
}

.site-footer {
  background: linear-gradient(180deg, #1e293b 0%, #111827 100%);
  color: #f3f4f6;
  font-family: 'Inter', sans-serif;
  border-top: 3px solid var(--primary-1, #2563eb);
  box-shadow: 0 -2px 10px rgba(0, 0, 0, 0.2);
  width: 100%;
  overflow-x: hidden;
  text-align: center;
}

/* --- Footer Main --- */
.site-footer .footer-main {
  display: flex;
  justify-content: center; 
  gap: 4rem;
  padding: 2.5rem 4rem;
  text-align: left;
  flex-wrap: wrap;
  padding: 2rem 1.5rem;
}

.site-footer .footer-section {
  max-width: 300px; 
  min-width: 200px;
  flex: 1 1 250px;
  text-align: left;
}

.footer-brand {
  display: flex;
  align-items: center;
  margin-bottom: 1rem;
}

.footer-logo {
  width: 48px;
  height: 48px;
  margin-right: 0.6rem;
}

.footer-brand-name {
  font-size: 1.4rem;
  font-weight: 700;
  background: var(--gradient-primary, linear-gradient(135deg, #4a92ea, #7c3aed));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

.site-footer .footer-section h4 {
  font-size: 1.1rem;
  font-weight: 600;
  margin-bottom: 0.75rem;
  color: var(--primary-1, #60a5fa);
}

.site-footer .footer-section ul {
  list-style: none;
  padding: 0;
  margin: 0;
}

.site-footer .footer-section li {
  margin-bottom: 0.5rem;
  color: #d1d5db;
}

.site-footer .footer-section a {
  color: #d1d5db;
  text-decoration: none;
  transition: color 0.2s ease;
}

.site-footer .footer-section a:hover {
  color: var(--primary-2, #a78bfa);
}

/* --- Footer Bottom --- */
.site-footer .footer-bottom {
  display: flex;
  justify-content: center;
  align-items: center;
  border-top: 1px solid rgba(255, 255, 255, 0.1);
  padding: 1rem 4rem;
  font-size: 0.95rem;
  background: rgba(0, 0, 0, 0.2);
  flex-wrap: wrap;
}

.site-footer .footer-note {
  color: #9ca3af;
  margin: 0;
}

.site-footer .footer-nav a {
  margin-left: 1rem;
  color: #9ca3af;
  text-decoration: none;
  transition: color 0.2s ease;
}

.site-footer .footer-nav a:hover {
  color: var(--primary-1, #60a5fa);
}

/* --- Responsive --- */
@media (max-width: 768px) {
  .site-footer .footer-section {
    text-align: center;
  }
  .site-footer .footer-main {
    flex-direction: column;
    text-align: left;
    align-items: center;
    gap: 0.25rem;
  }

  .footer-brand {
    justify-content: center;
  }
  
  .site-footer .footer-bottom {
    flex-direction: column;
    gap: 0.5rem;
    text-align: center;
    padding: 1rem 2rem;
  }

  .site-footer .footer-nav a {
    margin: 0 0.5rem;
  }
}

/* Contact form */
.contact-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 1.5rem;
}

.contact-form {
  background: white;
  padding: 1.5rem;
  border-radius: 10px;
  display: flex;
  flex-direction: column;
  gap: 1rem;
  box-shadow: 0 6px 18px rgba(15, 23, 42, 0.04);
}

.contact-form input,
.contact-form textarea {
  padding: 0.75rem;
  border: 1px solid #e6eefc;
  border-radius: 8px;
  font-family: inherit;
  transition: all 0.3s ease;
}

.contact-form input:focus,
.contact-form textarea:focus {
  outline: none;
  border-color: var(--primary-1);
  box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
}

.contact-info {
  background: white;
  padding: 1.5rem;
  border-radius: 10px;
  box-shadow: 0 6px 18px rgba(15, 23, 42, 0.04);
}

.contact-legal {
  font-size: 0.875rem;
  color: var(--muted);
  margin: 0.5rem 0;
}

/* Modal */
.modal {
  position: fixed;
  inset: 0;
  background: rgba(2, 6, 23, 0.5);
  display: none;
  align-items: center;
  justify-content: center;
  z-index: 1000;
  animation: fadeIn 0.3s ease;
}

.modal[aria-hidden="false"] {
  display: flex;
}

.modal-panel {
  background: white;
  padding: 1.5rem;
  border-radius: 10px;
  max-width: 480px;
  width: 90%;
  box-shadow: 0 20px 60px rgba(15, 23, 42, 0.3);
  animation: slideUp 0.3s ease;
}

.modal-actions {
  display: flex;
  justify-content: flex-end;
  gap: 0.75rem;
  margin-top: 1.5rem;
}

@keyframes fadeIn {
  from {
    opacity: 0;
  }
  to {
    opacity: 1;
  }
}

@keyframes slideUp {
  from {
    transform: translateY(20px);
    opacity: 0;
  }
  to {
    transform: translateY(0);
    opacity: 1;
  }
}

/* Toast */
.toast {
  position: fixed;
  right: 1rem;
  bottom: 1rem;
  min-width: 250px;
  background: #111827;
  color: white;
  padding: 1rem;
  border-radius: 8px;
  display: none;
  box-shadow: 0 10px 30px rgba(15, 23, 42, 0.3);
  animation: slideInUp 0.3s ease;
  z-index: 1001;
}

.toast[aria-hidden="false"] {
  display: block;
}

@keyframes slideInUp {
  from {
    transform: translateY(20px);
    opacity: 0;
  }
  to {
    transform: translateY(0);
    opacity: 1;
  }
}

/* Responsive */
@media (min-width: 768px) {
  .nav-toggle {
    display: none;
  }
  .nav {
    gap: 1.5rem;
  }
  .hero-inner {
    align-items: stretch;
  }
  .hero-copy h1 {
    font-size: 3rem;
  }
  .features-grid {
    grid-template-columns: repeat(2, 1fr);
  }
  .why-choose-grid {
    grid-template-columns: repeat(2, 1fr);
  }
  .pricing-grid {
    grid-template-columns: repeat(3, 1fr);
  }
  .contact-grid {
    grid-template-columns: 2fr 1fr;
  }
}

@media (max-width: 767px) {
  .header-inner {
    padding: 0.75rem 1rem; /* thêm padding trái phải */
  }

  .brand {
    margin-right: auto;
  }
  .nav {
    display: none;
    position: absolute;
    right: 1rem;
    top: 60px;
    background: white;
    padding: 1rem;
    border-radius: 8px;
    box-shadow: 0 10px 30px rgba(15, 23, 42, 0.08);
    flex-direction: column;
    gap: 0.5rem;
    width: 200px;
    z-index: 50;
  }

  #main-nav.open {
    display: flex;
  }

  #main-nav.open a {
    width: 100%;
    padding: 0.75rem;
  }

  .nav-toggle {
    display: block;
  }
  .hero-copy {
    padding: 1rem;
  }
  .hero-copy h1 {
    font-size: 1.75rem;
  }
  .hero-decor {
    display: none;
  }
  .hero-inner {
    flex-direction: column;
  }
  .hero-image img {
    max-width: 100%;
  }
  .section h2 {
    font-size: 1.5rem;
  }
  .footer-inner {
    flex-direction: column;
    gap: 1.5rem;
  }
}

/* Back to Top Button */
.back-to-top {
  position: fixed;
  bottom: 1.5rem;
  right: 1.5rem;
  z-index: 9999;
  width: 50px;
  height: 50px;
  background: var(--gradient-primary);
  color: white;
  border: none;
  border-radius: 50%;
  cursor: pointer;
  font-size: 1.2rem;
  box-shadow: var(--shadow-lg);
  transition: all 0.3s ease;
  opacity: 0;
  visibility: hidden;
  transform: translateY(100px);
}

.back-to-top.show {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}

.back-to-top:hover {
  transform: translateY(-3px) scale(1.1);
  box-shadow: 0 25px 30px -5px rgba(0, 0, 0, 0.15),
    0 15px 15px -5px rgba(0, 0, 0, 0.08);
}

@media (max-width: 768px) {
  .back-to-top {
    bottom: 1rem;
    right: 1rem;
    width: 40px;
    height: 40px;
    font-size: 0.9rem;
  }
}


.section-subtitle {
  max-width: 720px;
  margin: 0 auto 2rem auto;
  text-align: center;
  color: #555;
  font-size: 1.1rem;
  line-height: 1.7;
  padding: 0 1rem;
}

/* Tablet (<= 768px) */
@media (max-width: 768px) {
  .section-subtitle {
    font-size: 1rem;
    line-height: 1.6;
    margin-bottom: 1.5rem;
  }
}

/* Mobile nhỏ (<= 480px) */
@media (max-width: 480px) {
  .section-subtitle {
    font-size: 0.95rem;
    line-height: 1.5;
    padding: 0 0.5rem;
  }
}

.hero {
  position: relative;
  overflow: hidden;
  padding: 100px 0;
  text-align: center;
  color: #1a1a1a;
  background: linear-gradient(135deg, #f7faff 0%, #eef2ff 100%);
}

.hero-background {
  position: absolute;
  inset: 0;
  background: radial-gradient(circle at 20% 30%, rgba(74, 146, 234, 0.25), transparent 60%),
              radial-gradient(circle at 80% 70%, rgba(124, 58, 237, 0.25), transparent 60%);
  z-index: 0;
}

.hero-inner {
  position: relative;
  z-index: 2;
  max-width: 800px;
  margin: 0 auto;
  padding: 0 1rem;
}

.hero h1 {
  font-size: 2.4rem;
  line-height: 1.3;
  font-weight: 700;
  color: #4072c8;
  margin-bottom: 1rem;
}

.hero .lead {
  font-size: 1.1rem;
  color: #444;
  margin: 0 auto 2rem auto;
  max-width: 700px;
  text-align: center;
  line-height: 1.7;
}

.hero-ctas {
  display: flex;
  justify-content: center;
  gap: 1rem;
  flex-wrap: wrap;
}

.btn.primary {
  border-radius: 8px;
  padding: 12px 28px;
  font-weight: 600;
  box-shadow: 0 4px 10px rgba(124, 58, 237, 0.3);
  transition: transform 0.2s ease;
}
.btn.primary:hover {
  transform: scale(1.05);
}

.btn.outline {
  border: 2px solid #7c3aed;
  color: #7c3aed;
  border-radius: 8px;
  padding: 12px 26px;
  font-weight: 600;
  transition: all 0.2s ease;
}
.btn.outline:hover {
  background: #7c3aed;
  color: #fff;
}

/* Responsive */
@media (max-width: 768px) {
  .hero {
    padding: 80px 0;
  }
  .hero h1 {
    font-size: 1.9rem;
  }
  .hero .lead {
    font-size: 1rem;
  }
}

.experience {
  text-align: center;
  margin-top: 60px;
  padding: 2rem 1.5rem;
}

.experience-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 1.5rem;
  max-width: 1100px;
  margin: 0 auto;
}

.experience-card {
  margin: 0 auto;
  border-radius: 16px;
  padding: 30px 20px;
  text-align: center;
  box-shadow: 0 2px 10px rgba(0, 0, 0, 0.05);
  transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.experience-card:hover {
  transform: translateY(-4px);
  box-shadow: 0 4px 16px rgba(0, 0, 0, 0.1);
}

.experience-icon {
  width: 60px;
  height: 60px;
  border-radius: 50%;
  margin: 0 auto 15px;
  display: flex;
  align-items: center;
  justify-content: center;
  color: white;
  font-size: 24px;
}

.experience-card.blue .experience-icon {
  background-color: #2563eb; /* xanh dương */
}

.experience-card.green .experience-icon {
  background-color: #16a34a; /* xanh lá */
}

.experience-card.orange .experience-icon {
  background-color: #f59e0b; /* cam */
}

.experience-card.blue {
  background-color: #e0ecff;
}

.experience-card.green {
  background-color: #e7f7ee;
}

.experience-card.orange {
  background-color: #fff3e0;
}

.experience-card h3 {
  font-size: 1.2rem;
  font-weight: 600;
  margin-bottom: 10px;
  color: #222;
}

.experience-card p {
  color: #444;
  font-size: 0.95rem;
  line-height: 1.5;
}


.header-inner {
  padding: 0.75rem 1.5rem;
}

.brand {
  margin: 0;
  padding-left: 0.25rem;
}

@media (max-width: 768px) {
  .site-header {
    padding: 0 1rem;
  }

  .brand {
    display: flex;
    align-items: center;
    justify-content: flex-start;
  }

  .brand-text {
    font-size: 1.3rem;
  }
}