/* ============================================
   IoT Connect Center | Shared Stylesheet
   Mobile-first, CSS Variables, Grid + Flexbox
   ============================================ */

/* --- CSS Custom Properties --- */
:root {
  --primary: #0A2540;
  --primary-light: #1B3A5C;
  --accent: #2563EB;
  --accent-light: #3B82F6;
  --accent-dark: #1D4ED8;
  --success: #10B981;
  --warning: #F59E0B;
  --gray-50: #F8FAFC;
  --gray-100: #F1F5F9;
  --gray-200: #E2E8F0;
  --gray-300: #CBD5E1;
  --gray-400: #94A3B8;
  --gray-500: #64748B;
  --gray-600: #475569;
  --gray-700: #334155;
  --gray-800: #1E293B;
  --gray-900: #0F172A;
  --white: #FFFFFF;
  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
  --font-mono: 'SF Mono', 'Fira Code', 'Fira Mono', 'Roboto Mono', monospace;
  --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.05);
  --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -2px rgba(0, 0, 0, 0.1);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -4px rgba(0, 0, 0, 0.1);
  --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 8px 10px -6px rgba(0, 0, 0, 0.1);
  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 16px;
  --radius-xl: 24px;
  --max-width: 1200px;
  --header-height: 72px;
  --transition: 0.25s ease;
}

/* --- Reset & Base --- */
*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  scroll-behavior: smooth;
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: var(--font-sans);
  font-size: 16px;
  line-height: 1.6;
  color: var(--gray-800);
  background: var(--white);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

img {
  max-width: 100%;
  height: auto;
  display: block;
}

a {
  color: var(--accent);
  text-decoration: none;
  transition: color var(--transition);
}

a:hover {
  color: var(--accent-dark);
}

ul, ol {
  list-style: none;
}

/* --- Typography --- */
h1, h2, h3, h4, h5, h6 {
  color: var(--primary);
  line-height: 1.2;
  font-weight: 700;
}

h1 {
  font-size: 2.25rem;
  letter-spacing: -0.025em;
}

h2 {
  font-size: 1.75rem;
  letter-spacing: -0.02em;
}

h3 {
  font-size: 1.25rem;
}

h4 {
  font-size: 1.1rem;
}

p {
  color: var(--gray-600);
}

/* --- Utility --- */
.container {
  width: 100%;
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 20px;
}

.section {
  padding: 60px 0;
}

.section-header {
  text-align: center;
  margin-bottom: 48px;
}

.section-header h2 {
  margin-bottom: 12px;
}

.section-header p {
  font-size: 1.05rem;
  max-width: 640px;
  margin: 0 auto;
}

.badge {
  display: inline-block;
  font-size: 0.8rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--accent);
  background: rgba(37, 99, 235, 0.08);
  padding: 4px 14px;
  border-radius: 100px;
  margin-bottom: 12px;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  font-family: var(--font-sans);
  font-size: 0.95rem;
  font-weight: 600;
  padding: 12px 28px;
  border-radius: var(--radius-sm);
  border: none;
  cursor: pointer;
  transition: all var(--transition);
  text-decoration: none;
}

.btn-primary {
  background: var(--accent);
  color: var(--white);
}

.btn-primary:hover {
  background: var(--accent-dark);
  color: var(--white);
  transform: translateY(-1px);
  box-shadow: var(--shadow-md);
}

.btn-secondary {
  background: var(--white);
  color: var(--primary);
  border: 1.5px solid var(--gray-200);
}

.btn-secondary:hover {
  border-color: var(--accent);
  color: var(--accent);
  transform: translateY(-1px);
}

.btn-large {
  padding: 16px 36px;
  font-size: 1.05rem;
  border-radius: var(--radius-md);
}

/* --- Header / Navigation --- */
.site-header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: var(--header-height);
  background: rgba(255, 255, 255, 0.95);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--gray-200);
  z-index: 1000;
  display: flex;
  align-items: center;
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  width: 100%;
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 20px;
}

.logo {
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 1.15rem;
  font-weight: 700;
  color: var(--primary);
  text-decoration: none;
}

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

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

.nav-toggle span {
  display: block;
  width: 24px;
  height: 2px;
  background: var(--primary);
  border-radius: 2px;
  transition: all var(--transition);
}

.nav-menu {
  display: none;
  position: absolute;
  top: var(--header-height);
  left: 0;
  right: 0;
  background: var(--white);
  border-bottom: 1px solid var(--gray-200);
  padding: 16px 20px;
  box-shadow: var(--shadow-lg);
}

.nav-menu.active {
  display: block;
}

.nav-menu ul {
  display: flex;
  flex-direction: column;
  gap: 4px;
}

.nav-menu a {
  display: block;
  padding: 10px 12px;
  color: var(--gray-600);
  font-size: 0.95rem;
  font-weight: 500;
  border-radius: var(--radius-sm);
  transition: all var(--transition);
}

.nav-menu a:hover {
  color: var(--accent);
  background: var(--gray-50);
}

.nav-cta {
  margin-top: 12px;
  padding-top: 12px;
  border-top: 1px solid var(--gray-200);
}

/* --- Hero Section --- */
.hero {
  padding-top: calc(var(--header-height) + 48px);
  padding-bottom: 64px;
  background: linear-gradient(160deg, var(--primary) 0%, #0F3460 50%, var(--accent-dark) 100%);
  color: var(--white);
  position: relative;
  overflow: hidden;
}

.hero::before {
  content: '';
  position: absolute;
  top: -50%;
  right: -20%;
  width: 600px;
  height: 600px;
  background: radial-gradient(circle, rgba(37, 99, 235, 0.15) 0%, transparent 70%);
  border-radius: 50%;
}

.hero::after {
  content: '';
  position: absolute;
  bottom: -30%;
  left: -10%;
  width: 400px;
  height: 400px;
  background: radial-gradient(circle, rgba(16, 185, 129, 0.1) 0%, transparent 70%);
  border-radius: 50%;
}

.hero .container {
  position: relative;
  z-index: 1;
}

.hero-content {
  max-width: 640px;
}

.hero .badge {
  background: rgba(255, 255, 255, 0.12);
  color: var(--gray-200);
}

.hero h1 {
  color: var(--white);
  font-size: 2.5rem;
  margin-bottom: 20px;
}

.hero p {
  color: rgba(255, 255, 255, 0.8);
  font-size: 1.1rem;
  margin-bottom: 32px;
  line-height: 1.7;
}

.hero-buttons {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
}

.hero .btn-secondary {
  background: rgba(255, 255, 255, 0.1);
  border-color: rgba(255, 255, 255, 0.25);
  color: var(--white);
}

.hero .btn-secondary:hover {
  background: rgba(255, 255, 255, 0.2);
  border-color: rgba(255, 255, 255, 0.4);
  color: var(--white);
}

.hero-stats {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 16px;
  margin-top: 48px;
}

.stat {
  background: rgba(255, 255, 255, 0.07);
  border: 1px solid rgba(255, 255, 255, 0.1);
  border-radius: var(--radius-md);
  padding: 20px;
}

.stat-number {
  display: block;
  font-size: 1.75rem;
  font-weight: 700;
  color: var(--white);
  margin-bottom: 4px;
}

.stat-label {
  font-size: 0.85rem;
  color: rgba(255, 255, 255, 0.6);
}

/* --- About / Value Proposition --- */
.about {
  background: var(--white);
}

.about-grid {
  display: grid;
  gap: 24px;
}

.about-card {
  background: var(--gray-50);
  border: 1px solid var(--gray-200);
  border-radius: var(--radius-md);
  padding: 28px;
  transition: all var(--transition);
}

.about-card:hover {
  border-color: var(--accent);
  box-shadow: var(--shadow-md);
  transform: translateY(-2px);
}

.about-card h3 {
  margin-bottom: 8px;
}

.about-card p {
  font-size: 0.92rem;
  line-height: 1.6;
}

/* --- Features --- */
.features {
  background: var(--gray-50);
}

.features-grid {
  display: grid;
  gap: 20px;
}

.feature-card {
  background: var(--white);
  border: 1px solid var(--gray-200);
  border-radius: var(--radius-md);
  padding: 28px;
  transition: all var(--transition);
}

.feature-card:hover {
  box-shadow: var(--shadow-lg);
  transform: translateY(-2px);
}

.feature-card h3 {
  font-size: 1.1rem;
  margin-bottom: 8px;
}

.feature-card p {
  font-size: 0.9rem;
  line-height: 1.6;
}

/* --- How It Works --- */
.how-it-works {
  background: var(--white);
}

.steps {
  display: grid;
  gap: 32px;
  counter-reset: step;
}

.step {
  display: flex;
  gap: 20px;
  align-items: flex-start;
}

.step-number {
  flex-shrink: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  width: 48px;
  height: 48px;
  background: var(--accent);
  color: var(--white);
  border-radius: 50%;
  font-size: 1.1rem;
  font-weight: 700;
}

.step-content h3 {
  margin-bottom: 6px;
}

.step-content p {
  font-size: 0.92rem;
  line-height: 1.6;
}

/* --- Use Cases --- */
.use-cases {
  background: var(--gray-50);
}

.use-cases-grid {
  display: grid;
  gap: 20px;
}

.use-case-card {
  background: var(--white);
  border: 1px solid var(--gray-200);
  border-radius: var(--radius-md);
  padding: 28px;
  transition: all var(--transition);
}

.use-case-card:hover {
  box-shadow: var(--shadow-md);
  transform: translateY(-2px);
}

.use-case-card h3 {
  margin-bottom: 8px;
}

.use-case-card p {
  font-size: 0.9rem;
  line-height: 1.6;
  margin-bottom: 16px;
}

.use-case-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
}

.tag {
  font-size: 0.75rem;
  font-weight: 500;
  color: var(--gray-500);
  background: var(--gray-100);
  padding: 4px 10px;
  border-radius: 100px;
}

/* --- Security --- */
.security {
  background: var(--primary);
  color: var(--white);
}

.security .section-header h2 {
  color: var(--white);
}

.security .section-header p {
  color: rgba(255, 255, 255, 0.7);
}

.security-grid {
  display: grid;
  gap: 20px;
}

.security-card {
  background: rgba(255, 255, 255, 0.06);
  border: 1px solid rgba(255, 255, 255, 0.1);
  border-radius: var(--radius-md);
  padding: 28px;
  transition: all var(--transition);
}

.security-card:hover {
  background: rgba(255, 255, 255, 0.1);
  border-color: rgba(255, 255, 255, 0.2);
}

.security-card h3 {
  color: var(--white);
  margin-bottom: 8px;
  font-size: 1.05rem;
}

.security-card p {
  color: rgba(255, 255, 255, 0.65);
  font-size: 0.9rem;
  line-height: 1.6;
}

/* --- CTA / Contact --- */
.cta {
  background: linear-gradient(160deg, var(--accent-dark) 0%, var(--accent) 100%);
  color: var(--white);
  text-align: center;
  padding: 72px 0;
}

.cta h2 {
  color: var(--white);
  margin-bottom: 16px;
}

.cta p {
  color: rgba(255, 255, 255, 0.85);
  font-size: 1.05rem;
  max-width: 540px;
  margin: 0 auto 32px;
}

.cta-buttons {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 12px;
  margin-bottom: 40px;
}

.cta .btn-primary {
  background: var(--white);
  color: var(--accent);
}

.cta .btn-primary:hover {
  background: var(--gray-100);
  color: var(--accent-dark);
}

.cta .btn-secondary {
  background: transparent;
  border-color: rgba(255, 255, 255, 0.3);
  color: var(--white);
}

.cta .btn-secondary:hover {
  background: rgba(255, 255, 255, 0.1);
  border-color: rgba(255, 255, 255, 0.5);
  color: var(--white);
}

.contact-info {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 24px;
  font-size: 0.9rem;
  color: rgba(255, 255, 255, 0.8);
}

.contact-item {
  display: flex;
  align-items: center;
  gap: 6px;
}

/* --- Footer --- */
.site-footer {
  background: var(--gray-900);
  color: var(--gray-400);
  padding: 48px 0 24px;
}

.footer-grid {
  display: grid;
  gap: 32px;
  margin-bottom: 36px;
}

.footer-brand p {
  font-size: 0.88rem;
  margin-top: 12px;
  line-height: 1.6;
  color: var(--gray-400);
}

.footer-col h4 {
  color: var(--gray-200);
  font-size: 0.9rem;
  margin-bottom: 14px;
}

.footer-col ul {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.footer-col a {
  color: var(--gray-400);
  font-size: 0.88rem;
  transition: color var(--transition);
}

.footer-col a:hover {
  color: var(--white);
}

.footer-bottom {
  border-top: 1px solid var(--gray-800);
  padding-top: 20px;
  display: flex;
  flex-direction: column;
  gap: 12px;
  align-items: center;
  text-align: center;
  font-size: 0.82rem;
}

.footer-bottom-links {
  display: flex;
  gap: 20px;
}

.footer-bottom-links a {
  color: var(--gray-500);
  font-size: 0.82rem;
}

.footer-bottom-links a:hover {
  color: var(--gray-300);
}

/* --- Page-specific: Section Pages --- */
.page-hero {
  padding-top: calc(var(--header-height) + 48px);
  padding-bottom: 40px;
  background: var(--gray-50);
  border-bottom: 1px solid var(--gray-200);
}

.page-hero h1 {
  margin-bottom: 12px;
}

.page-hero p {
  font-size: 1.05rem;
  max-width: 640px;
}

.breadcrumb {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 0.85rem;
  margin-bottom: 20px;
  flex-wrap: wrap;
}

.breadcrumb a {
  color: var(--gray-500);
}

.breadcrumb a:hover {
  color: var(--accent);
}

.breadcrumb .separator {
  color: var(--gray-400);
}

.breadcrumb .current {
  color: var(--gray-700);
  font-weight: 500;
}

.page-content {
  padding: 48px 0;
}

/* --- Responsive: Tablet (768px+) --- */
@media (min-width: 768px) {
  h1 { font-size: 2.75rem; }
  h2 { font-size: 2rem; }

  .section { padding: 80px 0; }
  .container { padding: 0 32px; }

  .hero {
    padding-top: calc(var(--header-height) + 72px);
    padding-bottom: 80px;
  }

  .hero h1 { font-size: 3rem; }

  .hero-stats {
    grid-template-columns: repeat(4, 1fr);
  }

  .about-grid { grid-template-columns: repeat(2, 1fr); }
  .features-grid { grid-template-columns: repeat(2, 1fr); }
  .use-cases-grid { grid-template-columns: repeat(2, 1fr); }
  .security-grid { grid-template-columns: repeat(2, 1fr); }

  .footer-grid {
    grid-template-columns: 2fr 1fr 1fr;
  }

  .footer-bottom {
    flex-direction: row;
    justify-content: space-between;
  }

  .nav-toggle { display: none; }

  .nav-menu {
    display: flex;
    position: static;
    background: none;
    border: none;
    padding: 0;
    box-shadow: none;
  }

  .nav-menu ul {
    flex-direction: row;
    align-items: center;
    gap: 0;
  }

  .nav-menu a {
    padding: 8px 14px;
    font-size: 0.9rem;
  }

  .nav-cta {
    margin-top: 0;
    margin-left: 8px;
    padding-top: 0;
    border-top: none;
  }
}

/* --- Responsive: Desktop (1024px+) --- */
@media (min-width: 1024px) {
  h1 { font-size: 3.25rem; }
  h2 { font-size: 2.25rem; }

  .section { padding: 100px 0; }

  .hero {
    padding-top: calc(var(--header-height) + 96px);
    padding-bottom: 100px;
  }

  .hero h1 { font-size: 3.5rem; }
  .hero p { font-size: 1.15rem; }

  .about-grid { grid-template-columns: repeat(3, 1fr); }
  .features-grid { grid-template-columns: repeat(3, 1fr); }
  .use-cases-grid { grid-template-columns: repeat(3, 1fr); }
  .security-grid { grid-template-columns: repeat(3, 1fr); }

  .footer-grid {
    grid-template-columns: 2fr 1fr 1fr 1fr;
  }
}

/* --- Responsive: Wide (1280px+) --- */
@media (min-width: 1280px) {
  .hero h1 { font-size: 3.75rem; }

  .container { padding: 0 40px; }
}