/* ============================================================
   AI BUSINESS STUDIO LONDON — Design System
   ============================================================ */

:root {
  /* Colour - High-Key Monochrome */
  --c-bg: #fcfbf9;
  --c-surface: #ffffff;
  --c-ink: #111111;
  --c-muted: #666666;
  --c-border: #e8e5e0;
  --c-cream: #f5efe6;
  --c-accent: #000000;
  
  /* Typography */
  --font-serif: 'Cormorant Garamond', 'Times New Roman', serif;
  --font-sans: 'DM Sans', system-ui, sans-serif;

  /* Spacing */
  --space-xs: 0.5rem;
  --space-sm: 1rem;
  --space-md: 2rem;
  --space-lg: 4rem;
  --space-xl: 8rem;

  /* Motion */
  --ease: cubic-bezier(0.25, 0.46, 0.45, 0.94);
  --ease-out: cubic-bezier(0.16, 1, 0.3, 1);
}

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

html {
  scroll-behavior: smooth;
  -webkit-font-smoothing: antialiased;
}

body {
  font-family: var(--font-sans);
  background-color: var(--c-bg);
  color: var(--c-ink);
  font-size: 1rem;
  line-height: 1.7;
  overflow-x: hidden;
}

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

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

ul {
  list-style: none;
}

/* Typography */
h1, h2, h3, h4 {
  font-family: var(--font-serif);
  font-weight: 400;
  line-height: 1.15;
  letter-spacing: -0.01em;
}

h1 {
  font-size: clamp(2.5rem, 6vw, 4.5rem);
}

h2 {
  font-size: clamp(2rem, 4vw, 3.2rem);
}

h3 {
  font-size: clamp(1.4rem, 2.5vw, 1.8rem);
}

.label {
  font-family: var(--font-sans);
  font-size: 0.7rem;
  font-weight: 500;
  letter-spacing: 0.25em;
  text-transform: uppercase;
  color: var(--c-muted);
  display: inline-block;
  margin-bottom: 0.5rem;
}

/* Layout */
.container {
  max-width: 1100px;
  margin: 0 auto;
  padding: 0 var(--space-md);
}

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

/* Scroll Reveal */
.reveal {
  opacity: 0;
  transform: translateY(24px);
  transition: opacity 800ms var(--ease), transform 800ms var(--ease);
}

.reveal.visible {
  opacity: 1;
  transform: translateY(0);
}

.reveal-delay-1 {
  transition-delay: 150ms;
}

.reveal-delay-2 {
  transition-delay: 300ms;
}

/* Navigation */
.nav {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 100;
  transition: background 350ms var(--ease), box-shadow 350ms var(--ease),
    backdrop-filter 350ms var(--ease);
  border-bottom: 1px solid transparent;
}

.nav.scrolled {
  background: rgba(252, 251, 249, 0.92);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  box-shadow: 0 1px 0 var(--c-border);
}

.nav-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 1.5rem 2rem;
  max-width: 1300px;
  margin: 0 auto;
}

.nav-logo {
  font-family: var(--font-serif);
  font-size: 1.1rem;
  font-weight: 400;
  letter-spacing: 0.18em;
  color: white;
  text-transform: uppercase;
  transition: color 350ms var(--ease);
}

.nav.scrolled .nav-logo {
  color: var(--c-ink);
}

.nav-links {
  display: flex;
  align-items: center;
  gap: 2.5rem;
}

.nav-item a {
  font-family: var(--font-sans);
  font-size: 0.72rem;
  font-weight: 400;
  letter-spacing: 0.15em;
  text-transform: uppercase;
  color: rgba(255, 255, 255, 0.85);
  transition: color 350ms var(--ease);
}

.nav.scrolled .nav-item a {
  color: var(--c-ink);
}

.nav-item a:hover {
  color: white;
}

.nav.scrolled .nav-item a:hover {
  color: var(--c-muted);
}

/* Mobile Toggle */
.nav-toggle {
  display: none;
  flex-direction: column;
  gap: 5px;
  background: none;
  border: none;
  cursor: pointer;
  padding: 4px;
  z-index: 110;
}

.nav-toggle span {
  display: block;
  width: 22px;
  height: 1px;
  background: white;
  transition: all 300ms var(--ease);
}

.nav.scrolled .nav-toggle span {
  background: var(--c-ink);
}

/* Hero Section */
.hero {
  position: relative;
  height: 100vh;
  min-height: 550px;
  display: flex;
  align-items: center;
  justify-content: center;
  text-align: center;
  overflow: hidden;
}

.hero-bg {
  position: absolute;
  inset: 0;
  background-size: cover;
  background-position: center;
  background-repeat: no-repeat;
  transform: scale(1.03);
  transition: transform 7s var(--ease-out);
}

.hero-bg::after {
  content: '';
  position: absolute;
  inset: 0;
  background: rgba(0, 0, 0, 0.52);
}

.hero:hover .hero-bg {
  transform: scale(1);
}

.hero-content {
  position: relative;
  z-index: 1;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 1.5rem;
  max-width: 850px;
  padding: 0 var(--space-md);
}

.hero-title {
  font-family: var(--font-serif);
  font-size: clamp(2.5rem, 5.5vw, 4.5rem);
  font-weight: 300;
  line-height: 1.15;
  color: #ffffff;
  text-shadow: 0 2px 25px rgba(0, 0, 0, 0.45);
}

.hero-sub {
  font-family: var(--font-sans);
  font-size: 0.8rem;
  font-weight: 400;
  letter-spacing: 0.35em;
  text-transform: uppercase;
  color: rgba(255, 255, 255, 0.8);
}

.hero-scroll {
  position: absolute;
  bottom: 2.5rem;
  left: 50%;
  transform: translateX(-50%);
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.6rem;
  z-index: 1;
}

.hero-scroll span {
  font-family: var(--font-sans);
  font-size: 0.6rem;
  letter-spacing: 0.2em;
  text-transform: uppercase;
  color: rgba(255, 255, 255, 0.45);
}

.hero-scroll-line {
  width: 1px;
  height: 40px;
  background: linear-gradient(to bottom, rgba(255, 255, 255, 0.35), transparent);
  animation: scrollPulse 2.2s ease-in-out infinite;
}

@keyframes scrollPulse {
  0%, 100% {
    opacity: 0.4;
    transform: scaleY(1);
  }
  50% {
    opacity: 1;
    transform: scaleY(1.2);
  }
}

/* Manifesto Section */
.manifesto-section {
  background-color: var(--c-surface);
}

.manifesto-layout {
  display: grid;
  grid-template-columns: 1fr 2fr;
  gap: var(--space-lg);
  padding: var(--space-lg) 0;
}

.manifesto-line {
  font-family: var(--font-serif);
  font-size: clamp(1.4rem, 2.8vw, 2.2rem);
  font-weight: 300;
  line-height: 1.5;
  margin-bottom: var(--space-md);
  color: var(--c-ink);
}

.manifesto-line:last-child {
  margin-bottom: 0;
}

/* Trust Section */
.section-header {
  margin-bottom: var(--space-lg);
}

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

.section-header h2 {
  margin-top: 0.5rem;
  font-weight: 300;
}

.trust-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: var(--space-lg);
}

.trust-card {
  background: var(--c-surface);
  border: 1px solid var(--c-border);
  padding: var(--space-lg) var(--space-md);
  text-align: left;
  transition: transform 300ms var(--ease), box-shadow 300ms var(--ease), border-color 300ms var(--ease);
}

.trust-card:hover {
  transform: translateY(-4px);
  box-shadow: 0 16px 36px rgba(0,0,0,0.03);
  border-color: #bbbbbb;
}

.trust-card-title {
  font-family: var(--font-serif);
  font-size: 1.8rem;
  margin-bottom: var(--space-sm);
  color: var(--c-ink);
}

.trust-card-text {
  font-family: var(--font-sans);
  font-size: 0.92rem;
  color: var(--c-muted);
  line-height: 1.8;
}

/* Service Approach Section */
.services-list {
  display: flex;
  flex-direction: column;
  gap: var(--space-md);
  margin-top: var(--space-md);
}

.service-item {
  display: grid;
  grid-template-columns: 80px 1fr;
  padding: var(--space-md) 0;
  border-bottom: 1px solid var(--c-border);
  transition: transform 300ms var(--ease);
}

.service-item:hover {
  transform: translateX(8px);
}

.service-number {
  font-family: var(--font-serif);
  font-size: clamp(2rem, 4vw, 3rem);
  color: var(--c-muted);
  font-weight: 300;
  line-height: 1;
}

.service-details {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.service-title {
  font-family: var(--font-serif);
  font-size: 1.8rem;
  font-weight: 300;
}

.service-desc {
  font-family: var(--font-sans);
  font-size: 0.95rem;
  color: var(--c-muted);
  max-width: 60ch;
}

/* Contact Section */
.contact-section {
  text-align: center;
  background-color: var(--c-surface);
}

.contact-content {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--space-sm);
}

.contact-invitation {
  font-family: var(--font-serif);
  font-size: clamp(2rem, 4vw, 3rem);
  font-weight: 300;
  color: var(--c-ink);
}

/* Invitation Form styling */
.invitation-form {
  width: 100%;
  max-width: 600px;
  margin: 3rem auto 0;
  text-align: left;
}

.form-group-row {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 1.5rem;
}

@media (max-width: 576px) {
  .form-group-row {
    grid-template-columns: 1fr;
    gap: 0;
  }
}

.form-group {
  display: flex;
  flex-direction: column;
  gap: 0.4rem;
  margin-bottom: 1.5rem;
}

.invitation-form .form-label {
  font-family: var(--font-sans);
  font-size: 0.65rem;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--c-muted);
  font-weight: 500;
}

.invitation-form .form-input,
.invitation-form .form-textarea {
  font-family: var(--font-sans);
  font-size: 0.95rem;
  color: var(--c-ink);
  background: transparent;
  border: none;
  border-bottom: 1px solid var(--c-border);
  padding: 0.7rem 0;
  transition: border-color 200ms;
  outline: none;
  width: 100%;
  resize: none;
}

.invitation-form .form-input:focus,
.invitation-form .form-textarea:focus {
  border-color: var(--c-ink);
}

.invitation-form .form-textarea {
  min-height: 100px;
}

.form-actions {
  margin-top: 2rem;
  position: relative;
}

.invitation-form .btn-dark {
  background: var(--c-ink);
  color: var(--c-surface);
  font-family: var(--font-sans);
  font-size: 0.75rem;
  font-weight: 500;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  padding: 1.1rem 2rem;
  border: 1px solid var(--c-ink);
  cursor: pointer;
  transition: all 250ms var(--ease);
  width: 100%;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  position: relative;
}

.invitation-form .btn-dark:hover {
  background: transparent;
  color: var(--c-ink);
}

.btn-loader {
  display: none;
  align-items: center;
  justify-content: center;
  position: absolute;
  inset: 0;
  background: inherit;
  color: inherit;
}

.btn.loading .btn-loader {
  display: flex;
}

.btn.loading .submit-text {
  opacity: 0.35;
}

.spinner {
  width: 20px;
  height: 20px;
  animation: spinnerRotate 1.5s linear infinite;
}

.spinner circle {
  stroke-dasharray: 90, 150;
  stroke-dashoffset: 0;
  stroke: currentColor;
  animation: spinnerDash 1.5s ease-in-out infinite;
}

@keyframes spinnerRotate {
  100% { transform: rotate(360deg); }
}

@keyframes spinnerDash {
  0% {
    stroke-dasharray: 1, 150;
    stroke-dashoffset: 0;
  }
  50% {
    stroke-dasharray: 90, 150;
    stroke-dashoffset: -35;
  }
  100% {
    stroke-dasharray: 90, 150;
    stroke-dashoffset: -124;
  }
}

.form-result {
  text-align: center;
  padding: 3rem 2rem;
  background: var(--c-surface);
  border: 1px solid var(--c-border);
  margin-top: 3rem;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 1rem;
  max-width: 600px;
  margin-left: auto;
  margin-right: auto;
}

.form-result h3 {
  font-family: var(--font-serif);
  font-size: 1.8rem;
  color: var(--c-ink);
}

.form-result p {
  font-family: var(--font-serif);
  font-style: italic;
  color: var(--c-muted);
  max-width: 45ch;
  line-height: 1.6;
}

.alert-icon {
  width: 44px;
  height: 44px;
}

.success-result .alert-icon {
  color: #10b981;
}

.error-result .alert-icon {
  color: #ef4444;
}

/* Footer styling */
.footer {
  background: var(--c-bg);
  border-top: 1px solid var(--c-border);
  padding: var(--space-md) 0;
  text-align: center;
}

.footer-inner-minimal {
  font-family: var(--font-sans);
  font-size: 0.7rem;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--c-muted);
}

/* Mobile responsive menu overlays and updates */
@media (max-width: 768px) {
  .nav-links {
    position: fixed;
    top: 0;
    right: -100%;
    width: 80%;
    max-width: 300px;
    height: 100vh;
    background: var(--c-surface);
    flex-direction: column;
    align-items: flex-start;
    padding: 6rem 2rem 2rem;
    gap: 1.8rem;
    box-shadow: -10px 0 30px rgba(0,0,0,0.05);
    transition: right 350ms cubic-bezier(0.16, 1, 0.3, 1);
    z-index: 105;
  }

  .nav-links.open {
    right: 0;
  }

  .nav-overlay {
    position: fixed;
    inset: 0;
    background: rgba(0,0,0,0.4);
    backdrop-filter: blur(4px);
    opacity: 0;
    visibility: hidden;
    transition: opacity 300ms, visibility 300ms;
    z-index: 101;
  }

  .nav-overlay.open {
    opacity: 1;
    visibility: visible;
  }

  .nav-item a {
    color: var(--c-ink) !important;
    font-size: 0.9rem;
  }

  .nav-toggle {
    display: flex;
  }

  .nav-toggle.open span:nth-child(1) {
    transform: translateY(6px) rotate(45deg);
  }

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

  .nav-toggle.open span:nth-child(3) {
    transform: translateY(-6px) rotate(-45deg);
  }

  .nav-toggle span {
    background: white;
  }

  .nav.scrolled .nav-toggle span {
    background: var(--c-ink);
  }

  .manifesto-layout {
    grid-template-columns: 1fr;
    gap: var(--space-md);
  }

  .trust-grid {
    grid-template-columns: 1fr;
    gap: var(--space-md);
  }

  .service-item {
    grid-template-columns: 1fr;
    gap: 0.5rem;
  }
}