/* ============================================
   SheetBrain Landing Page
   Clean, modern, Google-inspired design
   ============================================ */

:root {
  --blue: #1a73e8;
  --blue-dark: #1557b0;
  --blue-light: #e8f0fe;
  --blue-surface: #f0f6ff;
  --green: #1e8e3e;
  --green-light: #e6f4ea;
  --red: #d93025;
  --amber: #f9ab00;
  --text: #202124;
  --text-secondary: #5f6368;
  --text-tertiary: #80868b;
  --surface: #ffffff;
  --surface-dim: #f8f9fa;
  --border: #e0e0e0;
  --border-light: #f0f0f0;
  --radius: 12px;
  --radius-sm: 8px;
  --radius-lg: 16px;
  --shadow-sm: 0 1px 3px rgba(0,0,0,0.08);
  --shadow-md: 0 4px 12px rgba(0,0,0,0.1);
  --shadow-lg: 0 8px 30px rgba(0,0,0,0.12);
  --max-width: 1120px;
  --transition: 0.2s cubic-bezier(0.4, 0, 0.2, 1);
}

/* Prevent font-swap layout shift */
@font-face {
  font-family: 'Inter';
  font-display: optional;
}

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

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

body {
  font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  color: var(--text);
  background: var(--surface);
  line-height: 1.6;
  font-size: 16px;
}

.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 24px;
}

a { color: var(--blue); text-decoration: none; }
a:hover { text-decoration: underline; }

code {
  font-family: 'SF Mono', 'Fira Code', 'Consolas', monospace;
  font-size: 0.9em;
  background: var(--blue-light);
  color: var(--blue-dark);
  padding: 2px 6px;
  border-radius: 4px;
}

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 12px 24px;
  border-radius: var(--radius-sm);
  font-weight: 600;
  font-size: 0.95rem;
  border: none;
  cursor: pointer;
  transition: all var(--transition);
  text-decoration: none;
  white-space: nowrap;
}

.btn-primary {
  background: var(--blue);
  color: white;
  box-shadow: 0 1px 3px rgba(26, 115, 232, 0.3);
}
.btn-primary:hover {
  background: var(--blue-dark);
  box-shadow: 0 4px 12px rgba(26, 115, 232, 0.35);
  transform: translateY(-1px);
  text-decoration: none;
}

.btn-secondary {
  background: var(--surface);
  color: var(--text);
  border: 1.5px solid var(--border);
}
.btn-secondary:hover {
  background: var(--surface-dim);
  border-color: var(--text-tertiary);
  text-decoration: none;
}

.btn-lg { padding: 14px 32px; font-size: 1rem; border-radius: var(--radius); }
.btn-block { width: 100%; }

/* Navigation */
.nav {
  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(--border-light);
}

.nav-inner {
  display: flex;
  align-items: center;
  height: 64px;
  gap: 32px;
}

.nav-brand {
  display: flex;
  align-items: center;
  gap: 10px;
  text-decoration: none;
  color: var(--text);
  flex-shrink: 0;
}

.nav-logo {
  display: flex;
  align-items: center;
}

.nav-name {
  font-weight: 700;
  font-size: 1.15rem;
  letter-spacing: -0.02em;
}

.nav-links {
  display: flex;
  gap: 28px;
  margin-left: auto;
}
.nav-links a {
  color: var(--text-secondary);
  font-size: 0.9rem;
  font-weight: 500;
  text-decoration: none;
  transition: color var(--transition);
}
.nav-links a:hover { color: var(--text); }

.nav-cta { margin-left: 12px; padding: 8px 20px; font-size: 0.875rem; }

.nav-toggle {
  display: none;
  flex-direction: column;
  gap: 5px;
  background: none;
  border: none;
  cursor: pointer;
  padding: 4px;
  margin-left: auto;
}
.nav-toggle span {
  display: block;
  width: 22px;
  height: 2px;
  background: var(--text);
  border-radius: 2px;
  transition: all var(--transition);
}

/* Hero */
.hero {
  padding: 140px 0 80px;
  text-align: center;
}

.hero-badge {
  display: inline-block;
  padding: 6px 16px;
  background: var(--blue-light);
  color: var(--blue);
  font-size: 0.85rem;
  font-weight: 600;
  border-radius: 20px;
  margin-bottom: 24px;
}

.hero h1 {
  font-size: clamp(2.2rem, 5vw, 3.5rem);
  font-weight: 800;
  line-height: 1.15;
  letter-spacing: -0.03em;
  margin-bottom: 20px;
  max-width: 720px;
  margin-left: auto;
  margin-right: auto;
}

.highlight {
  color: var(--blue);
  position: relative;
}

.hero-sub {
  font-size: 1.15rem;
  color: var(--text-secondary);
  max-width: 580px;
  margin: 0 auto 36px;
  line-height: 1.7;
}

.hero-actions {
  display: flex;
  gap: 12px;
  justify-content: center;
  flex-wrap: wrap;
  margin-bottom: 64px;
}

/* Demo Window */
.hero-demo { max-width: 600px; margin: 0 auto; }

.demo-window {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  overflow: hidden;
  box-shadow: var(--shadow-lg);
}

.demo-bar {
  display: flex;
  align-items: center;
  gap: 6px;
  padding: 12px 16px;
  background: var(--surface-dim);
  border-bottom: 1px solid var(--border-light);
}

.demo-dot {
  width: 10px;
  height: 10px;
  border-radius: 50%;
  background: var(--border);
}
.demo-dot:nth-child(1) { background: #ff5f57; }
.demo-dot:nth-child(2) { background: #febc2e; }
.demo-dot:nth-child(3) { background: #28c840; }

.demo-title {
  font-size: 0.8rem;
  color: var(--text-tertiary);
  margin-left: 8px;
}

.demo-content {
  padding: 24px 24px;
  height: 170px;
  overflow: hidden;
  opacity: 0;
  transition: opacity 0.4s ease;
}

.demo-content.ready {
  opacity: 1;
}

.demo-input {
  display: flex;
  align-items: baseline;
  gap: 8px;
  min-height: 28px;
}

.demo-output {
  display: flex;
  align-items: baseline;
  gap: 8px;
  min-height: 36px;
}

.demo-label {
  font-size: 0.8rem;
  color: var(--text-tertiary);
  font-weight: 500;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  flex-shrink: 0;
}

.demo-query {
  font-size: 1.05rem;
  color: var(--text);
  min-height: 1.3em;
}

.demo-cursor {
  color: var(--blue);
  animation: blink 1s step-end infinite;
  font-weight: 300;
}
@keyframes blink { 50% { opacity: 0; } }

.demo-arrow {
  display: flex;
  justify-content: center;
  align-items: center;
  padding: 10px 0;
}

.demo-arrow-icon {
  width: 32px;
  height: 32px;
  border-radius: 50%;
  background: var(--blue-light);
  display: flex;
  align-items: center;
  justify-content: center;
}

.demo-formula {
  font-size: 1rem;
  color: var(--green);
  padding: 4px 10px;
  border-radius: 6px;
  font-weight: 500;
  background: transparent;
  transition: background 0.15s ease;
}

.demo-formula.has-text {
  background: var(--green-light);
}

/* Hero Trust */
.hero-trust {
  display: flex;
  justify-content: center;
  gap: 8px;
  flex-wrap: wrap;
  font-size: 0.85rem;
  color: var(--text-tertiary);
  margin-bottom: 56px;
}
.trust-dot { color: var(--border); }

/* Pain Points */
.pain-points {
  padding: 80px 0;
  background: var(--surface-dim);
}

.pain-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 20px;
  max-width: 800px;
  margin: 0 auto 32px;
}

.pain-card {
  padding: 24px;
  background: var(--surface);
  border: 1px solid var(--border-light);
  border-radius: var(--radius);
  display: flex;
  gap: 16px;
  align-items: flex-start;
}

.pain-emoji {
  font-size: 1.5rem;
  flex-shrink: 0;
  line-height: 1;
}

.pain-card p {
  font-size: 0.92rem;
  color: var(--text-secondary);
  line-height: 1.6;
  margin: 0;
}

.pain-solution {
  text-align: center;
  font-size: 1.05rem;
  font-weight: 600;
  color: var(--green);
  max-width: 600px;
  margin: 0 auto;
}

/* Diff Badge */
.diff-badge {
  display: inline-block;
  padding: 5px 14px;
  background: var(--blue-light);
  color: var(--blue);
  font-size: 0.82rem;
  font-weight: 600;
  border-radius: 16px;
  margin-bottom: 16px;
  text-transform: uppercase;
  letter-spacing: 0.03em;
}

/* Comparison Table */
.comparison {
  padding: 100px 0;
}

.comparison-table-wrap {
  max-width: 800px;
  margin: 0 auto;
  overflow-x: auto;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--surface);
  box-shadow: var(--shadow-sm);
}

.comparison-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.9rem;
}

.comparison-table th,
.comparison-table td {
  padding: 14px 18px;
  text-align: left;
  border-bottom: 1px solid var(--border-light);
  border-right: 1px solid var(--border-light);
}

.comparison-table th:last-child,
.comparison-table td:last-child {
  border-right: none;
}

.comparison-table tbody tr:last-child td {
  border-bottom: none;
}

.comparison-table thead th {
  font-weight: 700;
  font-size: 0.85rem;
  color: var(--text-secondary);
  padding-bottom: 16px;
  border-bottom: 2px solid var(--border);
  background: var(--surface-dim);
}

.comparison-table thead th:first-child {
  border-radius: var(--radius) 0 0 0;
}

.comparison-table thead th.highlight-col {
  color: var(--blue);
  background: var(--blue-light);
  border-radius: 0 var(--radius) 0 0;
}

.comparison-table td:first-child {
  font-weight: 500;
  color: var(--text);
}

.comparison-table td.highlight-col,
.comparison-table tbody td:last-child {
  background: var(--blue-light);
  font-weight: 600;
  color: var(--blue-dark);
}

.comparison-table tbody tr:hover td {
  background: var(--surface-dim);
}

.comparison-table tbody tr:hover td:last-child {
  background: #dce8fd;
}

.comparison-table .yes { color: var(--green); font-weight: 600; }
.comparison-table .no { color: var(--red); }
.comparison-table .partial { color: var(--amber); }

/* Pricing Compare */
.pricing-compare {
  text-align: center;
  margin-top: 32px;
  font-size: 0.92rem;
  color: var(--text-secondary);
  max-width: 640px;
  margin-left: auto;
  margin-right: auto;
}

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

.section-header {
  text-align: center;
  margin-bottom: 56px;
}
.section-header h2 {
  font-size: clamp(1.75rem, 3.5vw, 2.25rem);
  font-weight: 800;
  letter-spacing: -0.02em;
  margin-bottom: 12px;
}
.section-header p {
  font-size: 1.1rem;
  color: var(--text-secondary);
  max-width: 500px;
  margin: 0 auto;
}

.features-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 28px;
}

.feature-card {
  padding: 32px 28px;
  border: 1px solid var(--border-light);
  border-radius: var(--radius-lg);
  transition: all var(--transition);
}
.feature-card:hover {
  border-color: var(--border);
  box-shadow: var(--shadow-md);
  transform: translateY(-2px);
}

.feature-icon {
  width: 52px;
  height: 52px;
  border-radius: var(--radius);
  display: flex;
  align-items: center;
  justify-content: center;
  margin-bottom: 20px;
}
.feature-icon.generate { background: #fef7e0; color: #f9ab00; }
.feature-icon.explain { background: var(--blue-light); color: var(--blue); }
.feature-icon.debug { background: #fce8e6; color: var(--red); }

.feature-card h3 {
  font-size: 1.2rem;
  font-weight: 700;
  margin-bottom: 10px;
  letter-spacing: -0.01em;
}

.feature-card > p {
  font-size: 0.92rem;
  color: var(--text-secondary);
  line-height: 1.65;
  margin-bottom: 20px;
}

.feature-example {
  background: var(--surface-dim);
  border-radius: var(--radius-sm);
  padding: 16px;
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.example-input {
  font-size: 0.85rem;
  color: var(--text-secondary);
}

.example-arrow {
  color: var(--text-tertiary);
  font-size: 0.8rem;
  text-align: center;
}

.example-output {
  font-size: 0.88rem;
  font-weight: 500;
}

.example-note {
  font-size: 0.8rem;
  color: var(--text-tertiary);
  font-style: italic;
}

/* Context Section */
.context-section {
  padding: 100px 0;
  background: var(--surface-dim);
}

.context-inner {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 64px;
  align-items: center;
}

.context-text h2 {
  font-size: clamp(1.75rem, 3.5vw, 2.25rem);
  font-weight: 800;
  letter-spacing: -0.02em;
  margin-bottom: 20px;
  line-height: 1.2;
}

.context-text > p {
  font-size: 1rem;
  color: var(--text-secondary);
  line-height: 1.7;
  margin-bottom: 16px;
}

.context-list {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 12px;
  margin-top: 24px;
}
.context-list li {
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 0.95rem;
  font-weight: 500;
}

.context-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  overflow: hidden;
  box-shadow: var(--shadow-md);
}

.context-card-header {
  padding: 14px 20px;
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--text-secondary);
  background: var(--surface-dim);
  border-bottom: 1px solid var(--border-light);
}

.context-card-body { padding: 20px; }

.context-tag-group {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-bottom: 16px;
}

.context-tag {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 6px 12px;
  background: var(--blue-light);
  color: var(--blue-dark);
  border-radius: 6px;
  font-size: 0.82rem;
  font-weight: 500;
}
.context-tag small {
  color: var(--text-tertiary);
  font-weight: 400;
  font-size: 0.75rem;
}

.context-meta {
  display: flex;
  gap: 16px;
  padding-top: 12px;
  border-top: 1px solid var(--border-light);
}
.context-meta span {
  font-size: 0.8rem;
  color: var(--text-tertiary);
  font-weight: 500;
}

/* How It Works */
.how-it-works { padding: 100px 0; }

.steps {
  display: flex;
  align-items: flex-start;
  gap: 0;
  max-width: 900px;
  margin: 0 auto;
}

.step {
  flex: 1;
  text-align: center;
  padding: 0 24px;
}

.step-number {
  width: 48px;
  height: 48px;
  border-radius: 50%;
  background: var(--blue);
  color: white;
  font-weight: 700;
  font-size: 1.2rem;
  display: flex;
  align-items: center;
  justify-content: center;
  margin: 0 auto 20px;
}

.step h3 {
  font-size: 1.1rem;
  font-weight: 700;
  margin-bottom: 10px;
}

.step p {
  font-size: 0.9rem;
  color: var(--text-secondary);
  line-height: 1.6;
}

.step-connector {
  width: 80px;
  height: 2px;
  background: var(--border);
  margin-top: 24px;
  flex-shrink: 0;
}

/* Custom Function Section */
.custom-fn {
  padding: 80px 0;
  background: var(--surface-dim);
}

.custom-fn-inner {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 48px;
  align-items: center;
}

.custom-fn-text h2 {
  font-size: clamp(1.5rem, 3vw, 2rem);
  font-weight: 800;
  letter-spacing: -0.02em;
  margin-bottom: 14px;
}

.custom-fn-text p {
  font-size: 0.95rem;
  color: var(--text-secondary);
  line-height: 1.7;
}

.custom-fn-demo {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 24px;
  box-shadow: var(--shadow-sm);
}

.cell-row {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 10px 14px;
  background: var(--surface-dim);
  border-radius: var(--radius-sm);
  border: 1px solid var(--border-light);
}

.cell-row.result {
  background: var(--green-light);
  border-color: #c8e6c9;
}

.cell-label {
  font-size: 0.8rem;
  font-weight: 700;
  color: var(--text-tertiary);
  flex-shrink: 0;
  width: 28px;
}

.cell-formula {
  font-size: 0.88rem;
  background: transparent;
  padding: 0;
  color: var(--text);
}

.cell-row.result .cell-formula {
  color: var(--green);
}

.cell-arrow {
  text-align: center;
  color: var(--text-tertiary);
  padding: 8px 0;
  font-size: 1.2rem;
}

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

.pricing-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 28px;
  max-width: 720px;
  margin: 0 auto;
}

.pricing-card {
  padding: 36px 32px;
  border: 1.5px solid var(--border);
  border-radius: var(--radius-lg);
  position: relative;
  transition: all var(--transition);
}
.pricing-card:hover {
  box-shadow: var(--shadow-md);
}

.pricing-card.featured {
  border-color: var(--blue);
  box-shadow: var(--shadow-md);
}

.pricing-badge {
  position: absolute;
  top: -12px;
  left: 50%;
  transform: translateX(-50%);
  background: var(--blue);
  color: white;
  font-size: 0.75rem;
  font-weight: 700;
  padding: 4px 16px;
  border-radius: 12px;
  text-transform: uppercase;
  letter-spacing: 0.04em;
}

.pricing-name {
  font-size: 1.1rem;
  font-weight: 700;
  color: var(--text-secondary);
  margin-bottom: 8px;
}

.pricing-price {
  font-size: 2.5rem;
  font-weight: 800;
  letter-spacing: -0.03em;
  margin-bottom: 4px;
}
.pricing-price span {
  font-size: 1rem;
  font-weight: 500;
  color: var(--text-tertiary);
}

.pricing-desc {
  font-size: 0.88rem;
  color: var(--text-tertiary);
  margin-bottom: 24px;
}

.pricing-features {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 12px;
  margin-bottom: 28px;
}
.pricing-features li {
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 0.9rem;
}

.pricing-annual {
  text-align: center;
  font-size: 0.82rem;
  color: var(--text-tertiary);
  margin-top: 12px;
}

/* FAQ */
.faq {
  padding: 100px 0;
  background: var(--surface-dim);
}

.faq-list {
  max-width: 680px;
  margin: 0 auto;
}

.faq-item {
  border-bottom: 1px solid var(--border);
  padding: 0;
}

.faq-item summary {
  padding: 20px 0;
  font-weight: 600;
  font-size: 1rem;
  cursor: pointer;
  list-style: none;
  display: flex;
  align-items: center;
  justify-content: space-between;
  color: var(--text);
  transition: color var(--transition);
}
.faq-item summary:hover { color: var(--blue); }

.faq-item summary::after {
  content: '+';
  font-size: 1.4rem;
  font-weight: 400;
  color: var(--text-tertiary);
  transition: transform var(--transition);
  flex-shrink: 0;
  margin-left: 16px;
}
.faq-item[open] summary::after {
  content: '\2212';
}

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

.faq-item p {
  padding: 0 0 20px;
  font-size: 0.92rem;
  color: var(--text-secondary);
  line-height: 1.7;
}

/* CTA */
.cta {
  padding: 100px 0;
  text-align: center;
}
.cta h2 {
  font-size: clamp(1.75rem, 3.5vw, 2.25rem);
  font-weight: 800;
  letter-spacing: -0.02em;
  margin-bottom: 12px;
}
.cta p {
  font-size: 1.05rem;
  color: var(--text-secondary);
  margin-bottom: 28px;
  max-width: 480px;
  margin-left: auto;
  margin-right: auto;
}

/* Footer */
.footer {
  padding: 64px 0 32px;
  background: var(--text);
  color: rgba(255, 255, 255, 0.7);
}

.footer-inner {
  display: flex;
  justify-content: space-between;
  gap: 48px;
  margin-bottom: 48px;
}

.footer-brand { max-width: 280px; }
.footer-brand .nav-name { color: white; }
.footer-brand .nav-brand { pointer-events: none; }

.footer-tagline {
  font-size: 0.88rem;
  margin-top: 10px;
  color: rgba(255, 255, 255, 0.5);
}

.footer-links {
  display: flex;
  gap: 64px;
}

.footer-col {
  display: flex;
  flex-direction: column;
  gap: 10px;
}
.footer-col h4 {
  font-size: 0.82rem;
  font-weight: 600;
  color: rgba(255, 255, 255, 0.4);
  text-transform: uppercase;
  letter-spacing: 0.06em;
  margin-bottom: 4px;
}
.footer-col a {
  color: rgba(255, 255, 255, 0.7);
  font-size: 0.88rem;
  text-decoration: none;
  transition: color var(--transition);
}
.footer-col a:hover { color: white; text-decoration: none; }

.footer-bottom {
  padding-top: 32px;
  border-top: 1px solid rgba(255, 255, 255, 0.1);
}
.footer-bottom p {
  font-size: 0.8rem;
  color: rgba(255, 255, 255, 0.35);
}

/* ============================================
   Responsive
   ============================================ */

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

  .nav-links.active {
    display: flex;
    flex-direction: column;
    position: absolute;
    top: 64px;
    left: 0;
    right: 0;
    background: var(--surface);
    padding: 16px 24px 24px;
    border-bottom: 1px solid var(--border);
    box-shadow: var(--shadow-md);
    gap: 16px;
  }

  .hero { padding: 110px 0 60px; }
  .hero h1 { font-size: 2rem; }
  .hero-sub { font-size: 1rem; }
  .hero-actions { flex-direction: column; align-items: center; }

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

  .features-grid { grid-template-columns: 1fr; gap: 20px; }

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

  .comparison-table { font-size: 0.8rem; }
  .comparison-table th, .comparison-table td { padding: 10px 12px; }

  .steps { flex-direction: column; gap: 24px; }
  .step-connector { width: 2px; height: 32px; margin: 0 auto; }

  .custom-fn-inner { grid-template-columns: 1fr; gap: 32px; }

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

  .footer-inner { flex-direction: column; gap: 32px; }
  .footer-links { flex-direction: column; gap: 32px; }

  .hero-trust { flex-direction: column; align-items: center; gap: 4px; }
  .trust-dot { display: none; }
}

@media (max-width: 480px) {
  body { font-size: 15px; }
  .container { padding: 0 16px; }
  .hero h1 { font-size: 1.75rem; }
  .feature-card { padding: 24px 20px; }
  .pricing-card { padding: 28px 24px; }
}