/* ==========================================================================
   CallStackAI Marketing Site — Dark Theme
   Colors: Electric Purple #6C63FF, Teal #00BFA5, Midnight #0A0F1E
   ========================================================================== */

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

:root {
  --purple: #6C63FF;
  --purple-light: #8B83FF;
  --purple-dark: #5A52E0;
  --teal: #00BFA5;
  --teal-light: #33CFBA;
  --teal-dark: #009E89;
  --midnight: #0A0F1E;
  --surface: #111827;
  --surface-light: #1A2236;
  --surface-lighter: #232D42;
  --text: #E2E8F0;
  --text-muted: #94A3B8;
  --text-dim: #64748B;
  --border: #1E293B;
  --white: #FFFFFF;
  --radius: 12px;
  --radius-sm: 8px;
  --shadow: 0 4px 24px rgba(0, 0, 0, 0.3);
  --shadow-lg: 0 12px 48px rgba(0, 0, 0, 0.4);
}

html {
  scroll-behavior: smooth;
  scroll-padding-top: 80px;
}

body {
  font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  background: var(--midnight);
  color: var(--text);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  overflow-x: hidden;
}

a {
  color: inherit;
  text-decoration: none;
}

ul {
  list-style: none;
}

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

/* --- Container --- */
.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 24px;
}

/* --- Buttons --- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  font-family: inherit;
  font-weight: 600;
  font-size: 0.95rem;
  border: 2px solid transparent;
  border-radius: var(--radius-sm);
  cursor: pointer;
  transition: all 0.2s ease;
  white-space: nowrap;
  text-decoration: none;
}

.btn-sm {
  padding: 8px 18px;
  font-size: 0.875rem;
}

.btn-lg {
  padding: 14px 32px;
  font-size: 1rem;
}

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

.btn-primary:hover {
  background: var(--purple-light);
  border-color: var(--purple-light);
  transform: translateY(-1px);
  box-shadow: 0 4px 16px rgba(108, 99, 255, 0.35);
}

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

.btn-outline:hover {
  border-color: var(--purple);
  color: var(--purple-light);
  transform: translateY(-1px);
}

.btn-block {
  width: 100%;
  padding: 14px 24px;
}

/* --- Navigation --- */
.nav {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 100;
  background: rgba(10, 15, 30, 0.85);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border);
}

.nav-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 72px;
}

.nav-logo {
  display: flex;
  align-items: center;
  gap: 10px;
  font-weight: 700;
  font-size: 1.1rem;
}

.logo-icon {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 36px;
  height: 36px;
  background: linear-gradient(135deg, var(--purple), var(--teal));
  border-radius: 8px;
  font-size: 0.8rem;
  font-weight: 800;
  color: var(--white);
}

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

.nav-links {
  display: flex;
  gap: 32px;
}

.nav-links a {
  font-size: 0.9rem;
  font-weight: 500;
  color: var(--text-muted);
  transition: color 0.2s;
}

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

.nav-actions {
  display: flex;
  gap: 12px;
}

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

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

.nav-toggle.active span:nth-child(1) {
  transform: rotate(45deg) translate(5px, 5px);
}

.nav-toggle.active span:nth-child(2) {
  opacity: 0;
}

.nav-toggle.active span:nth-child(3) {
  transform: rotate(-45deg) translate(5px, -5px);
}

.mobile-menu {
  display: none;
  position: fixed;
  top: 72px;
  left: 0;
  right: 0;
  background: var(--surface);
  border-bottom: 1px solid var(--border);
  padding: 24px;
  flex-direction: column;
  gap: 16px;
  z-index: 99;
}

.mobile-menu.open {
  display: flex;
}

.mobile-menu a {
  font-size: 1rem;
  color: var(--text-muted);
  padding: 8px 0;
}

/* --- Hero --- */
.hero {
  padding: 160px 0 100px;
  text-align: center;
  background:
    radial-gradient(ellipse 60% 50% at 50% 0%, rgba(108, 99, 255, 0.12) 0%, transparent 70%),
    radial-gradient(ellipse 40% 40% at 70% 20%, rgba(0, 191, 165, 0.06) 0%, transparent 60%);
}

.hero-badge {
  display: inline-block;
  padding: 6px 16px;
  background: rgba(108, 99, 255, 0.12);
  border: 1px solid rgba(108, 99, 255, 0.25);
  border-radius: 20px;
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--purple-light);
  margin-bottom: 24px;
  letter-spacing: 0.02em;
}

.hero h1 {
  font-size: clamp(2.5rem, 6vw, 4.2rem);
  font-weight: 800;
  line-height: 1.1;
  color: var(--white);
  margin-bottom: 24px;
  letter-spacing: -0.02em;
}

.hero-sub {
  font-size: clamp(1.05rem, 2vw, 1.25rem);
  color: var(--text-muted);
  max-width: 640px;
  margin: 0 auto 40px;
  line-height: 1.7;
}

.hero-actions {
  display: flex;
  gap: 16px;
  justify-content: center;
  flex-wrap: wrap;
  margin-bottom: 64px;
}

.hero-stats {
  display: flex;
  justify-content: center;
  gap: 48px;
  flex-wrap: wrap;
}

.stat {
  display: flex;
  flex-direction: column;
  align-items: center;
}

.stat-value {
  font-size: 1.8rem;
  font-weight: 800;
  color: var(--white);
}

.stat-label {
  font-size: 0.8rem;
  color: var(--text-dim);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  margin-top: 4px;
}

/* --- Section Header --- */
.section-header {
  text-align: center;
  max-width: 600px;
  margin: 0 auto 60px;
}

.section-header h2 {
  font-size: clamp(1.8rem, 4vw, 2.5rem);
  font-weight: 800;
  color: var(--white);
  margin-bottom: 16px;
  letter-spacing: -0.02em;
}

.section-header p {
  font-size: 1.1rem;
  color: var(--text-muted);
  line-height: 1.6;
}

/* --- Features --- */
.features {
  padding: 100px 0;
}

.features-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 24px;
}

.feature-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 32px;
  transition: all 0.3s ease;
}

.feature-card:hover {
  border-color: rgba(108, 99, 255, 0.3);
  transform: translateY(-4px);
  box-shadow: 0 8px 32px rgba(108, 99, 255, 0.08);
}

.feature-icon {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 48px;
  height: 48px;
  background: rgba(108, 99, 255, 0.1);
  border-radius: 10px;
  color: var(--purple);
  margin-bottom: 20px;
}

.feature-icon--teal {
  background: rgba(0, 191, 165, 0.1);
  color: var(--teal);
}

.feature-card h3 {
  font-size: 1.15rem;
  font-weight: 700;
  color: var(--white);
  margin-bottom: 10px;
}

.feature-card p {
  font-size: 0.92rem;
  color: var(--text-muted);
  line-height: 1.65;
}

/* --- How It Works --- */
.how-it-works {
  padding: 100px 0;
  background: var(--surface);
}

.steps {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 48px;
  text-align: center;
}

.step-number {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 64px;
  height: 64px;
  margin: 0 auto 24px;
  border-radius: 50%;
  background: linear-gradient(135deg, var(--purple), var(--teal));
  font-size: 1.5rem;
  font-weight: 800;
  color: var(--white);
}

.step h3 {
  font-size: 1.2rem;
  font-weight: 700;
  color: var(--white);
  margin-bottom: 12px;
}

.step p {
  font-size: 0.95rem;
  color: var(--text-muted);
  line-height: 1.65;
  max-width: 320px;
  margin: 0 auto;
}

/* --- Pricing --- */
.pricing {
  padding: 100px 0;
}

.pricing-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 24px;
  align-items: start;
}

.pricing-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 40px 32px;
  position: relative;
  transition: all 0.3s ease;
}

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

.pricing-card--featured {
  border-color: var(--purple);
  background: linear-gradient(180deg, rgba(108, 99, 255, 0.05), var(--surface));
}

.pricing-badge {
  position: absolute;
  top: -12px;
  left: 50%;
  transform: translateX(-50%);
  padding: 4px 16px;
  background: var(--purple);
  color: var(--white);
  font-size: 0.75rem;
  font-weight: 700;
  border-radius: 20px;
  text-transform: uppercase;
  letter-spacing: 0.06em;
}

.pricing-tier {
  font-size: 1rem;
  font-weight: 600;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.06em;
  margin-bottom: 16px;
}

.pricing-price {
  margin-bottom: 16px;
}

.price-amount {
  font-size: 3rem;
  font-weight: 800;
  color: var(--white);
  letter-spacing: -0.03em;
}

.price-period {
  font-size: 1rem;
  color: var(--text-dim);
}

.pricing-desc {
  font-size: 0.9rem;
  color: var(--text-muted);
  margin-bottom: 28px;
  line-height: 1.5;
}

.pricing-features {
  margin-bottom: 32px;
}

.pricing-features li {
  padding: 8px 0;
  font-size: 0.9rem;
  color: var(--text);
  border-bottom: 1px solid var(--border);
  position: relative;
  padding-left: 24px;
}

.pricing-features li::before {
  content: '';
  position: absolute;
  left: 0;
  top: 50%;
  transform: translateY(-50%);
  width: 16px;
  height: 16px;
  background: rgba(0, 191, 165, 0.15);
  border-radius: 50%;
}

.pricing-features li::after {
  content: '';
  position: absolute;
  left: 4px;
  top: 50%;
  transform: translateY(-50%);
  width: 8px;
  height: 4px;
  border-left: 2px solid var(--teal);
  border-bottom: 2px solid var(--teal);
  transform: translateY(-60%) rotate(-45deg);
}

/* --- Integrations --- */
.integrations {
  padding: 100px 0;
  background: var(--surface);
}

.integrations-grid {
  display: grid;
  grid-template-columns: repeat(6, 1fr);
  gap: 24px;
  max-width: 800px;
  margin: 0 auto;
}

.integration-item {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 12px;
  padding: 24px 16px;
  background: var(--surface-light);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  transition: all 0.2s ease;
}

.integration-item:hover {
  border-color: rgba(108, 99, 255, 0.3);
  transform: translateY(-2px);
}

.integration-item span {
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--text-muted);
}

/* --- CTA --- */
.cta {
  padding: 100px 0;
  text-align: center;
  background:
    radial-gradient(ellipse 60% 60% at 50% 100%, rgba(108, 99, 255, 0.1) 0%, transparent 70%);
}

.cta h2 {
  font-size: clamp(1.8rem, 4vw, 2.8rem);
  font-weight: 800;
  color: var(--white);
  margin-bottom: 16px;
}

.cta > .container > p {
  font-size: 1.1rem;
  color: var(--text-muted);
  margin-bottom: 40px;
}

.cta-form {
  display: flex;
  gap: 12px;
  max-width: 500px;
  margin: 0 auto 16px;
}

.cta-form input[type="email"] {
  flex: 1;
  padding: 14px 20px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  color: var(--white);
  font-size: 0.95rem;
  font-family: inherit;
  outline: none;
  transition: border-color 0.2s;
}

.cta-form input[type="email"]::placeholder {
  color: var(--text-dim);
}

.cta-form input[type="email"]:focus {
  border-color: var(--purple);
}

.cta-note {
  font-size: 0.8rem;
  color: var(--text-dim);
}

/* --- Footer --- */
.footer {
  padding: 64px 0 32px;
  border-top: 1px solid var(--border);
}

.footer-grid {
  display: grid;
  grid-template-columns: 2fr 1fr 1fr 1fr;
  gap: 48px;
  margin-bottom: 48px;
}

.footer-brand p {
  margin-top: 12px;
  font-size: 0.9rem;
  color: var(--text-dim);
  max-width: 280px;
  line-height: 1.6;
}

.footer-col h4 {
  font-size: 0.85rem;
  font-weight: 700;
  color: var(--text);
  text-transform: uppercase;
  letter-spacing: 0.06em;
  margin-bottom: 16px;
}

.footer-col a {
  display: block;
  font-size: 0.9rem;
  color: var(--text-dim);
  padding: 6px 0;
  transition: color 0.2s;
}

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

.footer-bottom {
  border-top: 1px solid var(--border);
  padding-top: 24px;
  text-align: center;
}

.footer-bottom p {
  font-size: 0.8rem;
  color: var(--text-dim);
}

.footer-bottom a {
  color: var(--teal);
}

.footer-bottom a:hover {
  text-decoration: underline;
}

/* --- Page template (for sub-pages) --- */
.page-header {
  padding: 140px 0 60px;
  text-align: center;
  background:
    radial-gradient(ellipse 50% 50% at 50% 0%, rgba(108, 99, 255, 0.1) 0%, transparent 70%);
}

.page-header h1 {
  font-size: clamp(2rem, 4vw, 3rem);
  font-weight: 800;
  color: var(--white);
  margin-bottom: 12px;
}

.page-header p {
  font-size: 1.1rem;
  color: var(--text-muted);
}

.page-content {
  padding: 60px 0 100px;
}

.page-content .container {
  max-width: 800px;
}

.page-content h2 {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--white);
  margin: 40px 0 16px;
}

.page-content h3 {
  font-size: 1.15rem;
  font-weight: 600;
  color: var(--white);
  margin: 28px 0 12px;
}

.page-content p {
  font-size: 0.95rem;
  color: var(--text-muted);
  line-height: 1.75;
  margin-bottom: 16px;
}

.page-content ul, .page-content ol {
  margin: 0 0 16px 24px;
  color: var(--text-muted);
  font-size: 0.95rem;
  line-height: 1.75;
}

.page-content ul {
  list-style: disc;
}

.page-content ol {
  list-style: decimal;
}

.page-content a {
  color: var(--purple-light);
}

.page-content a:hover {
  text-decoration: underline;
}

/* --- 404 page --- */
.error-page {
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  text-align: center;
  padding: 40px 24px;
}

.error-page h1 {
  font-size: 8rem;
  font-weight: 800;
  background: linear-gradient(135deg, var(--purple), var(--teal));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  line-height: 1;
  margin-bottom: 16px;
}

.error-page h2 {
  font-size: 1.5rem;
  color: var(--white);
  margin-bottom: 12px;
}

.error-page p {
  color: var(--text-muted);
  margin-bottom: 32px;
}

/* --- Responsive --- */
@media (max-width: 1024px) {
  .features-grid {
    grid-template-columns: repeat(2, 1fr);
  }

  .pricing-grid {
    grid-template-columns: repeat(2, 1fr);
  }

  .pricing-card:last-child {
    grid-column: 1 / -1;
    max-width: 400px;
    margin: 0 auto;
  }

  .integrations-grid {
    grid-template-columns: repeat(3, 1fr);
  }

  .footer-grid {
    grid-template-columns: 1fr 1fr;
    gap: 32px;
  }
}

@media (max-width: 768px) {
  .nav-links,
  .nav-actions {
    display: none;
  }

  .nav-toggle {
    display: flex;
  }

  .hero {
    padding: 120px 0 80px;
  }

  .features-grid {
    grid-template-columns: 1fr;
    gap: 16px;
  }

  .steps {
    grid-template-columns: 1fr;
    gap: 40px;
  }

  .pricing-grid {
    grid-template-columns: 1fr;
    max-width: 400px;
    margin: 0 auto;
  }

  .pricing-card:last-child {
    max-width: none;
  }

  .integrations-grid {
    grid-template-columns: repeat(3, 1fr);
    gap: 16px;
  }

  .cta-form {
    flex-direction: column;
  }

  .footer-grid {
    grid-template-columns: 1fr;
    gap: 32px;
  }

  .hero-stats {
    gap: 32px;
  }
}

@media (max-width: 480px) {
  .integrations-grid {
    grid-template-columns: repeat(2, 1fr);
  }

  .hero-stats {
    flex-direction: column;
    gap: 24px;
  }
}