/* ===================================================================
   Commerce Truth Layer — Design System
   Premium consulting + product demo hybrid
   =================================================================== */

/* --- Google Fonts --- */
@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700;800;900&display=swap');

/* --- Design Tokens --- */
:root {
  /* Kenvue-inspired warm palette */
  --coral-500: #E8553A;
  --coral-600: #D44A32;
  --coral-700: #BF3F2A;
  --coral-100: #FDEDEA;
  --coral-50:  #FEF6F4;

  --charcoal-900: #1A1A2E;
  --charcoal-800: #2D2D42;
  --charcoal-700: #3D3D56;
  --charcoal-600: #52526B;
  --charcoal-500: #6B6B82;
  --charcoal-400: #8E8EA0;
  --charcoal-300: #B0B0BE;

  --grey-100: #F7F7F9;
  --grey-200: #EEEFF2;
  --grey-300: #E2E3E8;
  --grey-50:  #FAFAFB;

  --white: #FFFFFF;
  --success: #2E9E6B;
  --info: #3B7DDD;

  /* Typography */
  --font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  --font-size-xs: 0.75rem;
  --font-size-sm: 0.875rem;
  --font-size-base: 1rem;
  --font-size-lg: 1.125rem;
  --font-size-xl: 1.25rem;
  --font-size-2xl: 1.5rem;
  --font-size-3xl: 1.875rem;
  --font-size-4xl: 2.25rem;
  --font-size-5xl: 3rem;
  --font-size-6xl: 3.75rem;

  /* Spacing */
  --space-1: 0.25rem;
  --space-2: 0.5rem;
  --space-3: 0.75rem;
  --space-4: 1rem;
  --space-5: 1.25rem;
  --space-6: 1.5rem;
  --space-8: 2rem;
  --space-10: 2.5rem;
  --space-12: 3rem;
  --space-16: 4rem;
  --space-20: 5rem;
  --space-24: 6rem;

  /* Shadows */
  --shadow-sm: 0 1px 2px rgba(26, 26, 46, 0.04);
  --shadow-md: 0 4px 12px rgba(26, 26, 46, 0.06);
  --shadow-lg: 0 8px 24px rgba(26, 26, 46, 0.08);
  --shadow-xl: 0 16px 48px rgba(26, 26, 46, 0.10);
  --shadow-card: 0 2px 8px rgba(26, 26, 46, 0.05), 0 1px 3px rgba(26, 26, 46, 0.04);
  --shadow-card-hover: 0 8px 24px rgba(26, 26, 46, 0.10), 0 2px 6px rgba(26, 26, 46, 0.06);

  /* Borders */
  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 14px;
  --radius-xl: 20px;
  --radius-full: 999px;

  /* Transitions */
  --transition-fast: 150ms cubic-bezier(0.4, 0, 0.2, 1);
  --transition-base: 250ms cubic-bezier(0.4, 0, 0.2, 1);
  --transition-slow: 400ms cubic-bezier(0.4, 0, 0.2, 1);
}

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

html {
  scroll-behavior: smooth;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  font-size: 16px;
}

body {
  font-family: var(--font-family);
  color: var(--charcoal-800);
  background: var(--white);
  line-height: 1.7;
  overflow-x: hidden;
}

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

a {
  color: var(--coral-500);
  text-decoration: none;
  transition: color var(--transition-fast);
}

a:hover {
  color: var(--coral-700);
}

/* --- Utility Classes --- */
.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 var(--space-6);
}

.section {
  padding: var(--space-24) 0;
}

.section--alt {
  background: var(--grey-50);
}

.section--coral-tint {
  background: var(--coral-50);
}

.section__label {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  font-size: var(--font-size-xs);
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.12em;
  color: var(--coral-500);
  margin-bottom: var(--space-4);
  padding: var(--space-2) var(--space-4);
  background: var(--coral-100);
  border-radius: var(--radius-full);
}

.section__title {
  font-size: var(--font-size-4xl);
  font-weight: 800;
  color: var(--charcoal-900);
  line-height: 1.2;
  margin-bottom: var(--space-4);
  letter-spacing: -0.025em;
}

.section__subtitle {
  font-size: var(--font-size-lg);
  color: var(--charcoal-500);
  max-width: 680px;
  line-height: 1.7;
}

.text-center {
  text-align: center;
}

.text-center .section__subtitle {
  margin-left: auto;
  margin-right: auto;
}

/* --- Navigation --- */
.nav {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 1000;
  background: rgba(255, 255, 255, 0.92);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border-bottom: 1px solid var(--grey-200);
  transition: box-shadow var(--transition-base);
}

.nav.scrolled {
  box-shadow: var(--shadow-md);
}

.nav__inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 var(--space-6);
  height: 64px;
}

.nav__brand {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  font-weight: 700;
  font-size: var(--font-size-base);
  color: var(--charcoal-900);
  text-decoration: none;
}

.nav__brand-icon {
  width: 32px;
  height: 32px;
  background: linear-gradient(135deg, var(--coral-500), var(--coral-600));
  border-radius: var(--radius-sm);
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--white);
  font-weight: 800;
  font-size: var(--font-size-sm);
}

.nav__links {
  display: flex;
  align-items: center;
  gap: var(--space-1);
  list-style: none;
}

.nav__links a {
  display: block;
  padding: var(--space-2) var(--space-3);
  font-size: var(--font-size-sm);
  font-weight: 500;
  color: var(--charcoal-600);
  border-radius: var(--radius-sm);
  transition: all var(--transition-fast);
}

.nav__links a:hover {
  color: var(--coral-500);
  background: var(--coral-50);
}

.nav__toggle {
  display: none;
  background: none;
  border: none;
  cursor: pointer;
  padding: var(--space-2);
  color: var(--charcoal-700);
}

.nav__toggle svg {
  width: 24px;
  height: 24px;
}

/* --- Hero --- */
.hero {
  padding: calc(64px + var(--space-20)) 0 var(--space-20);
  background: linear-gradient(170deg, var(--white) 0%, var(--coral-50) 40%, var(--grey-50) 100%);
  position: relative;
  overflow: hidden;
}

.hero::before {
  content: '';
  position: absolute;
  top: -30%;
  right: -10%;
  width: 600px;
  height: 600px;
  background: radial-gradient(circle, rgba(232, 85, 58, 0.06) 0%, transparent 70%);
  border-radius: 50%;
  pointer-events: none;
}

.hero::after {
  content: '';
  position: absolute;
  bottom: -20%;
  left: -5%;
  width: 400px;
  height: 400px;
  background: radial-gradient(circle, rgba(232, 85, 58, 0.04) 0%, transparent 70%);
  border-radius: 50%;
  pointer-events: none;
}

.hero__inner {
  max-width: 900px;
  margin: 0 auto;
  padding: 0 var(--space-6);
  position: relative;
  z-index: 1;
}

.hero__badge {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-2) var(--space-5);
  background: var(--white);
  border: 1px solid var(--grey-200);
  border-radius: var(--radius-full);
  font-size: var(--font-size-sm);
  font-weight: 500;
  color: var(--charcoal-600);
  margin-bottom: var(--space-8);
  box-shadow: var(--shadow-sm);
}

.hero__badge-dot {
  width: 8px;
  height: 8px;
  background: var(--success);
  border-radius: 50%;
  animation: pulse 2s ease-in-out infinite;
}

@keyframes pulse {
  0%, 100% { opacity: 1; }
  50% { opacity: 0.4; }
}

.hero__title {
  font-size: var(--font-size-5xl);
  font-weight: 900;
  color: var(--charcoal-900);
  line-height: 1.1;
  letter-spacing: -0.03em;
  margin-bottom: var(--space-6);
}

.hero__title span {
  background: linear-gradient(135deg, var(--coral-500), var(--coral-700));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero__description {
  font-size: var(--font-size-xl);
  color: var(--charcoal-500);
  line-height: 1.7;
  margin-bottom: var(--space-10);
  max-width: 720px;
}

.hero__actions {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-3);
  margin-bottom: var(--space-12);
}

/* --- Buttons --- */
.btn {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-3) var(--space-6);
  font-family: var(--font-family);
  font-size: var(--font-size-sm);
  font-weight: 600;
  border-radius: var(--radius-md);
  border: none;
  cursor: pointer;
  transition: all var(--transition-base);
  text-decoration: none;
  line-height: 1.5;
}

.btn--primary {
  background: linear-gradient(135deg, var(--coral-500), var(--coral-600));
  color: var(--white);
  box-shadow: 0 2px 8px rgba(232, 85, 58, 0.25);
}

.btn--primary:hover {
  background: linear-gradient(135deg, var(--coral-600), var(--coral-700));
  box-shadow: 0 4px 16px rgba(232, 85, 58, 0.35);
  transform: translateY(-1px);
  color: var(--white);
}

.btn--secondary {
  background: var(--white);
  color: var(--charcoal-700);
  border: 1px solid var(--grey-300);
  box-shadow: var(--shadow-sm);
}

.btn--secondary:hover {
  background: var(--grey-50);
  border-color: var(--charcoal-300);
  transform: translateY(-1px);
  color: var(--charcoal-900);
}

.btn--ghost {
  background: transparent;
  color: var(--coral-500);
  padding: var(--space-3) var(--space-4);
}

.btn--ghost:hover {
  background: var(--coral-50);
}

/* --- Explainer boxes in hero --- */
.hero__explainers {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--space-4);
  margin-bottom: var(--space-8);
}

.explainer-box {
  padding: var(--space-6);
  background: var(--white);
  border: 1px solid var(--grey-200);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-card);
  transition: all var(--transition-base);
}

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

.explainer-box__label {
  display: inline-block;
  font-size: var(--font-size-xs);
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--coral-500);
  background: var(--coral-100);
  padding: var(--space-1) var(--space-3);
  border-radius: var(--radius-full);
  margin-bottom: var(--space-3);
}

.explainer-box__title {
  font-size: var(--font-size-lg);
  font-weight: 700;
  color: var(--charcoal-900);
  margin-bottom: var(--space-2);
}

.explainer-box__text {
  font-size: var(--font-size-sm);
  color: var(--charcoal-500);
  line-height: 1.6;
}

/* --- Disclaimer note --- */
.hero__note {
  padding: var(--space-4) var(--space-5);
  background: var(--grey-100);
  border-left: 3px solid var(--charcoal-300);
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  font-size: var(--font-size-sm);
  color: var(--charcoal-500);
  line-height: 1.6;
}

.hero__note strong {
  color: var(--charcoal-700);
}

/* --- Cards Grid --- */
.cards-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--space-6);
  margin-top: var(--space-10);
}

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

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

/* --- Card --- */
.card {
  background: var(--white);
  border: 1px solid var(--grey-200);
  border-radius: var(--radius-lg);
  padding: var(--space-8);
  box-shadow: var(--shadow-card);
  transition: all var(--transition-base);
  position: relative;
  overflow: hidden;
}

.card:hover {
  box-shadow: var(--shadow-card-hover);
  transform: translateY(-3px);
  border-color: var(--grey-300);
}

.card__icon {
  width: 48px;
  height: 48px;
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
  margin-bottom: var(--space-5);
  font-size: 1.5rem;
}

.card__icon--coral {
  background: var(--coral-100);
  color: var(--coral-500);
}

.card__icon--grey {
  background: var(--grey-200);
  color: var(--charcoal-600);
}

.card__icon--blue {
  background: #E8F0FE;
  color: var(--info);
}

.card__icon--green {
  background: #E6F5ED;
  color: var(--success);
}

.card__title {
  font-size: var(--font-size-base);
  font-weight: 700;
  color: var(--charcoal-900);
  margin-bottom: var(--space-2);
}

.card__text {
  font-size: var(--font-size-sm);
  color: var(--charcoal-500);
  line-height: 1.6;
}

.card__tag {
  display: inline-block;
  font-size: var(--font-size-xs);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--charcoal-400);
  margin-top: var(--space-4);
}

/* --- Fragmented card with warning stripe --- */
.card--fragmented {
  border-top: 3px solid var(--coral-500);
}

.card--fragmented .card__icon {
  background: var(--coral-100);
  color: var(--coral-600);
}

/* --- Architecture Diagram --- */
.architecture {
  overflow-x: auto;
  margin-top: var(--space-10);
}

.arch-diagram {
  display: flex;
  flex-direction: column;
  gap: var(--space-6);
  min-width: 800px;
}

.arch-layer {
  display: flex;
  align-items: stretch;
  gap: var(--space-4);
}

.arch-layer__label {
  writing-mode: vertical-rl;
  text-orientation: mixed;
  transform: rotate(180deg);
  font-size: var(--font-size-xs);
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--charcoal-400);
  padding: var(--space-4) var(--space-2);
  background: var(--grey-100);
  border-radius: var(--radius-sm);
  display: flex;
  align-items: center;
  justify-content: center;
  min-width: 36px;
}

.arch-layer__content {
  flex: 1;
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-3);
}

.arch-box {
  flex: 1;
  min-width: 140px;
  padding: var(--space-4) var(--space-5);
  border-radius: var(--radius-md);
  font-size: var(--font-size-sm);
  font-weight: 500;
  text-align: center;
  transition: all var(--transition-base);
}

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

.arch-box--source {
  background: var(--grey-100);
  border: 1px solid var(--grey-300);
  color: var(--charcoal-700);
}

.arch-box--ingest {
  background: #FFF4E6;
  border: 1px solid #FFD8A8;
  color: #7E5500;
}

.arch-box--truth {
  background: var(--coral-100);
  border: 2px solid var(--coral-500);
  color: var(--coral-700);
  font-weight: 700;
  box-shadow: 0 4px 16px rgba(232, 85, 58, 0.12);
}

.arch-box--publish {
  background: #E6F5ED;
  border: 1px solid #A8DAC1;
  color: #1A6E3E;
}

.arch-box--surface {
  background: #E8F0FE;
  border: 1px solid #AECBFA;
  color: #1A4F9E;
}

/* Arrow divider between layers */
.arch-arrow {
  display: flex;
  justify-content: center;
  padding: var(--space-2) 0;
  color: var(--charcoal-300);
}

.arch-arrow svg {
  width: 24px;
  height: 24px;
}

/* --- Truth layer centerpiece --- */
.truth-layer {
  background: var(--white);
  border: 2px solid var(--coral-500);
  border-radius: var(--radius-xl);
  padding: var(--space-8);
  margin-top: var(--space-10);
  box-shadow: 0 8px 32px rgba(232, 85, 58, 0.08);
  position: relative;
}

.truth-layer::before {
  content: 'COMMERCE PRODUCT TRUTH LAYER';
  position: absolute;
  top: -14px;
  left: 50%;
  transform: translateX(-50%);
  background: var(--coral-500);
  color: var(--white);
  font-size: var(--font-size-xs);
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.12em;
  padding: var(--space-1) var(--space-5);
  border-radius: var(--radius-full);
  white-space: nowrap;
}

.truth-layer__grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--space-4);
}

.truth-layer__item {
  display: flex;
  align-items: flex-start;
  gap: var(--space-3);
  padding: var(--space-4);
  background: var(--coral-50);
  border-radius: var(--radius-md);
  font-size: var(--font-size-sm);
  color: var(--charcoal-700);
  transition: all var(--transition-fast);
}

.truth-layer__item:hover {
  background: var(--coral-100);
}

.truth-layer__item-icon {
  flex-shrink: 0;
  width: 28px;
  height: 28px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1rem;
}

.truth-layer__item-text {
  font-weight: 500;
  line-height: 1.4;
}

/* --- Demo Examples --- */
.demo-card {
  background: var(--white);
  border: 1px solid var(--grey-200);
  border-radius: var(--radius-lg);
  overflow: hidden;
  box-shadow: var(--shadow-card);
  transition: all var(--transition-base);
}

.demo-card:hover {
  box-shadow: var(--shadow-card-hover);
  transform: translateY(-3px);
}

.demo-card__header {
  padding: var(--space-5) var(--space-6);
  background: linear-gradient(135deg, var(--coral-50), var(--grey-50));
  border-bottom: 1px solid var(--grey-200);
  display: flex;
  align-items: center;
  gap: var(--space-3);
}

.demo-card__brand {
  font-weight: 700;
  font-size: var(--font-size-sm);
  color: var(--coral-600);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.demo-card__type {
  font-size: var(--font-size-xs);
  color: var(--charcoal-400);
  background: var(--white);
  padding: var(--space-1) var(--space-3);
  border-radius: var(--radius-full);
  border: 1px solid var(--grey-200);
}

.demo-card__body {
  padding: var(--space-6);
}

.demo-card__question {
  font-size: var(--font-size-lg);
  font-weight: 700;
  color: var(--charcoal-900);
  margin-bottom: var(--space-3);
}

.demo-card__answer {
  font-size: var(--font-size-sm);
  color: var(--charcoal-500);
  line-height: 1.7;
  margin-bottom: var(--space-4);
}

.demo-card__meta {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
}

.demo-card__tag {
  font-size: var(--font-size-xs);
  font-weight: 500;
  padding: var(--space-1) var(--space-3);
  border-radius: var(--radius-full);
  background: var(--grey-100);
  color: var(--charcoal-500);
  border: 1px solid var(--grey-200);
}

.demo-card__tag--brand {
  background: var(--coral-50);
  color: var(--coral-600);
  border-color: var(--coral-100);
}

/* --- Readiness Checklist --- */
.checklist {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: var(--space-4);
  margin-top: var(--space-10);
}

.checklist__item {
  display: flex;
  align-items: flex-start;
  gap: var(--space-3);
  padding: var(--space-5);
  background: var(--white);
  border: 1px solid var(--grey-200);
  border-radius: var(--radius-md);
  transition: all var(--transition-base);
}

.checklist__item:hover {
  box-shadow: var(--shadow-card);
  border-color: var(--grey-300);
}

.checklist__check {
  flex-shrink: 0;
  width: 24px;
  height: 24px;
  border-radius: 50%;
  background: var(--success);
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--white);
  font-size: 0.75rem;
  margin-top: 2px;
}

.checklist__text {
  font-size: var(--font-size-sm);
  color: var(--charcoal-700);
  font-weight: 500;
  line-height: 1.5;
}

/* --- Why Public Hosting --- */
.hosting-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: var(--space-6);
  margin-top: var(--space-10);
}

.hosting-card {
  display: flex;
  align-items: flex-start;
  gap: var(--space-5);
  padding: var(--space-8);
  background: var(--white);
  border: 1px solid var(--grey-200);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-card);
  transition: all var(--transition-base);
}

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

.hosting-card__icon {
  flex-shrink: 0;
  width: 48px;
  height: 48px;
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.5rem;
}

.hosting-card__text h3 {
  font-size: var(--font-size-base);
  font-weight: 700;
  color: var(--charcoal-900);
  margin-bottom: var(--space-2);
}

.hosting-card__text p {
  font-size: var(--font-size-sm);
  color: var(--charcoal-500);
  line-height: 1.6;
}

/* --- Footer --- */
.footer {
  background: var(--charcoal-900);
  padding: var(--space-16) 0 var(--space-8);
  color: var(--charcoal-300);
}

.footer__grid {
  display: grid;
  grid-template-columns: 2fr 1fr 1fr;
  gap: var(--space-12);
  margin-bottom: var(--space-12);
}

.footer__brand {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  margin-bottom: var(--space-4);
  color: var(--white);
  font-weight: 700;
  font-size: var(--font-size-lg);
}

.footer__brand-icon {
  width: 36px;
  height: 36px;
  background: linear-gradient(135deg, var(--coral-500), var(--coral-600));
  border-radius: var(--radius-sm);
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--white);
  font-weight: 800;
  font-size: var(--font-size-sm);
}

.footer__description {
  font-size: var(--font-size-sm);
  line-height: 1.7;
  color: var(--charcoal-400);
  max-width: 400px;
}

.footer__heading {
  font-size: var(--font-size-sm);
  font-weight: 700;
  color: var(--white);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  margin-bottom: var(--space-5);
}

.footer__links {
  list-style: none;
}

.footer__links li {
  margin-bottom: var(--space-3);
}

.footer__links a {
  color: var(--charcoal-400);
  font-size: var(--font-size-sm);
  transition: color var(--transition-fast);
}

.footer__links a:hover {
  color: var(--coral-500);
}

.footer__bottom {
  padding-top: var(--space-8);
  border-top: 1px solid var(--charcoal-800);
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  align-items: center;
  gap: var(--space-4);
}

.footer__copyright {
  font-size: var(--font-size-xs);
  color: var(--charcoal-500);
}

.footer__note {
  font-size: var(--font-size-xs);
  color: var(--charcoal-500);
  max-width: 500px;
  text-align: right;
  line-height: 1.6;
}

/* --- Divider --- */
.divider {
  width: 60px;
  height: 3px;
  background: linear-gradient(90deg, var(--coral-500), transparent);
  border-radius: var(--radius-full);
  margin: var(--space-6) 0;
}

.divider--center {
  margin-left: auto;
  margin-right: auto;
}

/* --- Scroll-to-top --- */
.scroll-top {
  position: fixed;
  bottom: 24px;
  right: 24px;
  width: 44px;
  height: 44px;
  background: var(--coral-500);
  color: var(--white);
  border: none;
  border-radius: 50%;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  box-shadow: 0 4px 16px rgba(232, 85, 58, 0.3);
  opacity: 0;
  visibility: hidden;
  transform: translateY(10px);
  transition: all var(--transition-base);
  z-index: 100;
}

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

.scroll-top:hover {
  background: var(--coral-600);
  transform: translateY(-2px);
}

/* --- Animations --- */
.fade-in {
  opacity: 0;
  transform: translateY(20px);
  transition: opacity 0.6s ease, transform 0.6s ease;
}

.fade-in.visible {
  opacity: 1;
  transform: translateY(0);
}

/* --- Responsive --- */
@media (max-width: 1024px) {
  .cards-grid,
  .cards-grid--4col {
    grid-template-columns: repeat(2, 1fr);
  }

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

  .footer__grid {
    grid-template-columns: 1fr 1fr;
  }
}

@media (max-width: 768px) {
  .hero__title {
    font-size: var(--font-size-4xl);
  }

  .section__title {
    font-size: var(--font-size-3xl);
  }

  .hero__explainers {
    grid-template-columns: 1fr;
  }

  .cards-grid,
  .cards-grid--2col,
  .cards-grid--4col {
    grid-template-columns: 1fr;
  }

  .truth-layer__grid {
    grid-template-columns: 1fr;
  }

  .hosting-grid {
    grid-template-columns: 1fr;
  }

  .nav__links {
    display: none;
    position: absolute;
    top: 64px;
    left: 0;
    right: 0;
    background: var(--white);
    border-bottom: 1px solid var(--grey-200);
    padding: var(--space-4) var(--space-6);
    flex-direction: column;
    box-shadow: var(--shadow-lg);
  }

  .nav__links.open {
    display: flex;
  }

  .nav__toggle {
    display: block;
  }

  .footer__grid {
    grid-template-columns: 1fr;
  }

  .footer__bottom {
    flex-direction: column;
    text-align: center;
  }

  .footer__note {
    text-align: center;
  }

  .arch-diagram {
    /* allow scrolling on mobile */
  }
}

@media (max-width: 480px) {
  .hero__title {
    font-size: var(--font-size-3xl);
  }

  .hero__actions {
    flex-direction: column;
  }

  .btn {
    justify-content: center;
  }

  .section {
    padding: var(--space-16) 0;
  }

  .container {
    padding: 0 var(--space-4);
  }
}

/* --- Print --- */
@media print {
  .nav, .scroll-top {
    display: none;
  }

  .section {
    padding: var(--space-8) 0;
    page-break-inside: avoid;
  }

  .card, .demo-card {
    box-shadow: none;
    border: 1px solid #ccc;
  }
}