:root {
  --color-primary: #0d6e6e;
  --color-primary-dark: #095555;
  --color-primary-light: #14a3a3;
  --color-accent: #f0a500;
  --color-bg: #f8fafb;
  --color-surface: #ffffff;
  --color-text: #1a2b3c;
  --color-text-muted: #5a6b7d;
  --color-border: #e2e8f0;
  --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.06);
  --shadow-md: 0 4px 20px rgba(13, 110, 110, 0.1);
  --shadow-lg: 0 12px 40px rgba(13, 110, 110, 0.15);
  --radius: 12px;
  --radius-lg: 20px;
  --font: "Be Vietnam Pro", system-ui, sans-serif;
  --header-height: 72px;
}

*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  scroll-behavior: smooth;
  scroll-padding-top: var(--header-height);
}

body {
  font-family: var(--font);
  color: var(--color-text);
  background: var(--color-bg);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

.container {
  width: 100%;
  max-width: 1140px;
  margin: 0 auto;
  padding: 0 1.25rem;
}

a {
  color: var(--color-primary);
  text-decoration: none;
  transition: color 0.2s;
}

a:hover {
  color: var(--color-primary-light);
}

/* Header */
.header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 100;
  background: rgba(255, 255, 255, 0.92);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--color-border);
  height: var(--header-height);
}

.nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 100%;
}

.logo {
  display: flex;
  align-items: center;
  gap: 0.6rem;
  color: var(--color-text);
  font-weight: 600;
}

.logo:hover {
  color: var(--color-text);
}

.logo-img {
  height: 42px;
  width: auto;
  object-fit: contain;
}

.logo-img-sm {
  height: 30px;
}

.logo-text {
  font-size: 1rem;
}

.nav-links {
  display: flex;
  align-items: center;
  gap: 2rem;
  list-style: none;
}

.nav-links a {
  color: var(--color-text-muted);
  font-size: 0.95rem;
  font-weight: 500;
}

.nav-links a:hover {
  color: var(--color-primary);
}

.menu-toggle {
  display: none;
  flex-direction: column;
  gap: 5px;
  background: none;
  border: none;
  cursor: pointer;
  padding: 4px;
}

.menu-toggle span {
  display: block;
  width: 24px;
  height: 2px;
  background: var(--color-text);
  border-radius: 2px;
  transition: 0.3s;
}

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 0.75rem 1.5rem;
  border-radius: 10px;
  font-family: var(--font);
  font-size: 0.95rem;
  font-weight: 600;
  cursor: pointer;
  border: 2px solid transparent;
  transition: all 0.2s;
}

.btn-primary {
  background: linear-gradient(135deg, var(--color-primary), var(--color-primary-light));
  color: #fff;
  box-shadow: var(--shadow-md);
}

.btn-primary:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-lg);
  color: #fff;
}

.btn-outline {
  background: transparent;
  border-color: var(--color-primary);
  color: var(--color-primary);
}

.btn-outline:hover {
  background: var(--color-primary);
  color: #fff;
}

.btn-sm {
  padding: 0.5rem 1.25rem;
  font-size: 0.9rem;
}

.btn-full {
  width: 100%;
}

/* Hero */
.hero {
  position: relative;
  min-height: 100vh;
  display: flex;
  align-items: center;
  padding-top: var(--header-height);
  overflow: hidden;
}

.hero-bg {
  position: absolute;
  inset: 0;
  background:
    radial-gradient(ellipse 80% 60% at 70% 20%, rgba(13, 110, 110, 0.12), transparent),
    radial-gradient(ellipse 60% 50% at 10% 80%, rgba(240, 165, 0, 0.08), transparent),
    linear-gradient(180deg, #eef7f7 0%, var(--color-bg) 100%);
  z-index: 0;
}

.hero-content {
  position: relative;
  z-index: 1;
  padding: 4rem 1.25rem;
}

.hero-badge {
  display: inline-block;
  padding: 0.4rem 1rem;
  background: rgba(13, 110, 110, 0.1);
  color: var(--color-primary);
  border-radius: 50px;
  font-size: 0.85rem;
  font-weight: 600;
  margin-bottom: 1.5rem;
}

.hero h1 {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
  margin-bottom: 1.25rem;
}

.hero-product {
  font-size: clamp(2.5rem, 6vw, 4rem);
  font-weight: 700;
  background: linear-gradient(135deg, var(--color-primary-dark), var(--color-primary-light));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  line-height: 1.1;
}

.hero-tagline {
  font-size: clamp(1.1rem, 2.5vw, 1.5rem);
  font-weight: 500;
  color: var(--color-text-muted);
}

.hero-desc {
  font-size: 1.1rem;
  color: var(--color-text-muted);
  max-width: 600px;
  margin-bottom: 2rem;
}

.hero-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 1rem;
  margin-bottom: 3.5rem;
}

.hero-stats {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1.5rem;
  max-width: 700px;
  padding: 1.5rem;
  background: var(--color-surface);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-md);
  border: 1px solid var(--color-border);
}

.stat {
  text-align: center;
}

.stat-value {
  display: block;
  font-size: clamp(0.95rem, 2vw, 1.15rem);
  font-weight: 700;
  color: var(--color-primary);
  margin-bottom: 0.25rem;
  line-height: 1.3;
}

.stat-label {
  font-size: 0.8rem;
  color: var(--color-text-muted);
}

/* Sections */
.section {
  padding: 5rem 0;
}

.section-header {
  max-width: 640px;
  margin-bottom: 3rem;
}

.section-header.center {
  text-align: center;
  margin-left: auto;
  margin-right: auto;
}

.section-label {
  display: inline-block;
  font-size: 0.8rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--color-primary);
  margin-bottom: 0.75rem;
}

.section-header h2 {
  font-size: clamp(1.75rem, 4vw, 2.25rem);
  font-weight: 700;
  margin-bottom: 1rem;
  line-height: 1.2;
}

.section-header p {
  color: var(--color-text-muted);
  font-size: 1.05rem;
}

/* About */
.about-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1.5rem;
}

.about-card {
  background: var(--color-surface);
  padding: 2rem;
  border-radius: var(--radius-lg);
  border: 1px solid var(--color-border);
  transition: transform 0.2s, box-shadow 0.2s;
}

.about-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-md);
}

.card-icon {
  font-size: 2rem;
  margin-bottom: 1rem;
}

.about-card h3 {
  font-size: 1.15rem;
  margin-bottom: 0.75rem;
}

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

/* Product */
.product {
  background: var(--color-surface);
}

.product-lead {
  font-size: 1.05rem;
  color: var(--color-text-muted);
  line-height: 1.7;
}

.product-intro {
  margin-bottom: 2.5rem;
}

.product-intro h2 {
  font-size: clamp(1.75rem, 4vw, 2.25rem);
  margin-bottom: 1rem;
}

.feature-list {
  display: flex;
  flex-direction: column;
  gap: 1.25rem;
}

.feature-card {
  display: flex;
  gap: 1.5rem;
  padding: 2rem;
  background: var(--color-bg);
  border-radius: var(--radius-lg);
  border: 1px solid var(--color-border);
  transition: box-shadow 0.2s;
}

.feature-card:hover {
  box-shadow: var(--shadow-sm);
}

.feature-highlight {
  background: linear-gradient(135deg, rgba(13, 110, 110, 0.06), rgba(20, 163, 163, 0.04));
  border-color: rgba(13, 110, 110, 0.2);
}

.feature-number {
  flex-shrink: 0;
  width: 48px;
  height: 48px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--color-primary);
  color: #fff;
  font-weight: 700;
  font-size: 0.9rem;
  border-radius: 12px;
}

.feature-body h3 {
  font-size: 1.15rem;
  margin-bottom: 0.75rem;
  color: var(--color-text);
}

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

.feature-body ul {
  margin-top: 1rem;
  padding-left: 1.25rem;
  color: var(--color-text-muted);
  font-size: 0.95rem;
}

.feature-body li {
  margin-bottom: 0.6rem;
}

.feature-body li strong {
  color: var(--color-text);
}

/* Modules — chuẩn 3176 BYT */
.modules {
  background: var(--color-bg);
}

.module-list {
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
}

.module-item {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  overflow: hidden;
  transition: box-shadow 0.2s;
}

.module-item[open] {
  box-shadow: var(--shadow-sm);
}

.module-item summary {
  display: flex;
  align-items: center;
  gap: 1rem;
  padding: 1.25rem 1.5rem;
  font-weight: 600;
  font-size: 1.05rem;
  cursor: pointer;
  list-style: none;
  user-select: none;
}

.module-item summary::-webkit-details-marker {
  display: none;
}

.module-item summary::after {
  content: "+";
  margin-left: auto;
  font-size: 1.25rem;
  font-weight: 400;
  color: var(--color-primary);
  transition: transform 0.2s;
}

.module-item[open] summary::after {
  content: "−";
}

.module-num {
  flex-shrink: 0;
  width: 36px;
  height: 36px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--color-primary);
  color: #fff;
  font-size: 0.8rem;
  font-weight: 700;
  border-radius: 8px;
}

.module-body {
  padding: 0 1.5rem 1.5rem;
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 1.25rem;
  border-top: 1px solid var(--color-border);
  padding-top: 1.25rem;
  margin: 0 1.5rem 1.5rem;
}

.module-group h4 {
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--color-primary-dark);
  margin-bottom: 0.6rem;
}

.module-group ul,
.module-flat {
  list-style: none;
  padding: 0;
  margin: 0;
}

.module-group ul li,
.module-flat li {
  position: relative;
  padding: 0.35rem 0 0.35rem 1.1rem;
  font-size: 0.9rem;
  color: var(--color-text-muted);
}

.module-group ul li::before,
.module-flat li::before {
  content: "•";
  position: absolute;
  left: 0;
  color: var(--color-primary-light);
  font-weight: 700;
}

.module-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem;
}

.module-tags li {
  padding: 0.3rem 0.75rem;
  background: rgba(13, 110, 110, 0.08);
  border-radius: 50px;
  font-size: 0.85rem;
  color: var(--color-primary-dark);
}

.module-tags li::before {
  display: none;
}

.module-grid-list {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 0 1rem;
  grid-column: 1 / -1;
}

/* Benefits */
.benefits-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 1.5rem;
}

.benefit-item {
  text-align: center;
  padding: 2rem 1.25rem;
  background: var(--color-surface);
  border-radius: var(--radius-lg);
  border: 1px solid var(--color-border);
}

.benefit-icon {
  font-size: 2.5rem;
  display: block;
  margin-bottom: 1rem;
}

.benefit-item h3 {
  font-size: 1.05rem;
  margin-bottom: 0.5rem;
}

.benefit-item p {
  font-size: 0.9rem;
  color: var(--color-text-muted);
}

/* Tech banner */
.tech-stack {
  padding: 3rem 0;
}

.tech-banner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 2rem;
  padding: 2.5rem 3rem;
  background: linear-gradient(135deg, var(--color-primary-dark), var(--color-primary));
  border-radius: var(--radius-lg);
  color: #fff;
}

.tech-content h2 {
  font-size: 1.5rem;
  margin-bottom: 0.75rem;
}

.tech-content p {
  opacity: 0.9;
  font-size: 0.95rem;
  max-width: 520px;
}

.tech-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 0.6rem;
  flex-shrink: 0;
}

.tag {
  padding: 0.4rem 1rem;
  background: rgba(255, 255, 255, 0.15);
  border: 1px solid rgba(255, 255, 255, 0.25);
  border-radius: 50px;
  font-size: 0.85rem;
  font-weight: 500;
}

/* Contact */
.contact-card {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 3rem;
  padding: 3rem;
  background: var(--color-surface);
  border-radius: var(--radius-lg);
  border: 1px solid var(--color-border);
  box-shadow: var(--shadow-md);
}

.contact-info h2 {
  font-size: 1.75rem;
  margin-bottom: 1rem;
}

.contact-info > p {
  color: var(--color-text-muted);
  margin-bottom: 1.5rem;
}

.contact-details {
  list-style: none;
}

.contact-details li {
  padding: 0.5rem 0;
  font-size: 0.95rem;
  color: var(--color-text-muted);
}

.contact-details strong {
  color: var(--color-text);
}

.contact-form h3 {
  font-size: 1.15rem;
  margin-bottom: 1.25rem;
}

.form-group {
  margin-bottom: 1rem;
}

.form-group label {
  display: block;
  font-size: 0.85rem;
  font-weight: 600;
  margin-bottom: 0.4rem;
  color: var(--color-text);
}

.form-group input,
.form-group textarea {
  width: 100%;
  padding: 0.75rem 1rem;
  border: 1px solid var(--color-border);
  border-radius: 8px;
  font-family: var(--font);
  font-size: 0.95rem;
  transition: border-color 0.2s;
  background: var(--color-bg);
}

.form-group input:focus,
.form-group textarea:focus {
  outline: none;
  border-color: var(--color-primary);
  background: var(--color-surface);
}

.form-note {
  margin-top: 1rem;
  text-align: center;
  color: var(--color-primary);
  font-weight: 500;
  font-size: 0.9rem;
}

.form-error {
  color: #c0392b;
}

.form-honey {
  position: absolute;
  left: -9999px;
  opacity: 0;
  height: 0;
  width: 0;
  pointer-events: none;
}

/* Footer */
.footer {
  padding: 2rem 0;
  background: var(--color-text);
  color: rgba(255, 255, 255, 0.7);
}

.footer-inner {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.75rem;
  text-align: center;
}

.footer-brand {
  display: flex;
  align-items: center;
  gap: 0.6rem;
  color: #fff;
  font-weight: 600;
}

.footer-copy {
  font-size: 0.85rem;
}

/* Responsive */
@media (max-width: 900px) {
  .about-grid,
  .benefits-grid {
    grid-template-columns: repeat(2, 1fr);
  }

  .tech-banner {
    flex-direction: column;
    text-align: center;
    padding: 2rem;
  }

  .tech-content p {
    max-width: none;
  }

  .tech-tags {
    justify-content: center;
  }

  .contact-card {
    grid-template-columns: 1fr;
    padding: 2rem;
  }
}

@media (max-width: 640px) {
  .nav-links {
    display: none;
    position: absolute;
    top: var(--header-height);
    left: 0;
    right: 0;
    flex-direction: column;
    background: var(--color-surface);
    padding: 1.5rem;
    gap: 1rem;
    border-bottom: 1px solid var(--color-border);
    box-shadow: var(--shadow-md);
  }

  .nav-links.open {
    display: flex;
  }

  .menu-toggle {
    display: flex;
  }

  .hero-stats {
    grid-template-columns: 1fr;
    gap: 1rem;
  }

  .about-grid,
  .benefits-grid {
    grid-template-columns: 1fr;
  }

  .feature-card {
    flex-direction: column;
    gap: 1rem;
  }

  .hero-actions {
    flex-direction: column;
  }

  .hero-actions .btn {
    width: 100%;
  }

  .module-body {
    grid-template-columns: 1fr;
    margin: 0 1rem 1rem;
    padding: 1rem 0 0;
  }

  .module-item summary {
    padding: 1rem;
    font-size: 0.95rem;
  }
}