/* ========================================
   GBrain — Dark tech landing page
   Inspired by autoresearch.lol
   ======================================== */

:root {
  --bg-primary: #0a0a0f;
  --bg-secondary: #111118;
  --bg-tertiary: #1a1a24;
  --bg-card: #13131f;
  --border: #252536;
  --border-hover: #3a3a55;

  --text-primary: #f0f0f5;
  --text-secondary: #a0a0b5;
  --text-muted: #6b6b85;

  --accent: #8b5cf6;
  --accent-light: #a78bfa;
  --accent-dark: #7c3aed;
  --accent-glow: rgba(139, 92, 246, 0.25);

  --blue: #3b82f6;
  --blue-light: #60a5fa;
  --green: #22c55e;

  --radius: 12px;
  --radius-sm: 8px;
  --max-width: 1100px;
  --font: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
}

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
  scroll-padding-top: 58px;
}

body {
  font-family: var(--font);
  background: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

::selection {
  background: var(--accent);
  color: #fff;
}

/* ========================================
   Navigation
   ======================================== */

.nav {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 100;
  background: rgba(10, 10, 15, 0.85);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border-bottom: 1px solid var(--border);
}

.nav-container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 24px;
  min-height: 52px;
  height: auto;
  padding-block: 8px;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.nav-logo img {
  display: block;
  height: 24px;
  width: auto;
}

.nav-links {
  display: flex;
  gap: 28px;
}

.nav-links a {
  color: var(--text-secondary);
  text-decoration: none;
  font-size: 13px;
  font-weight: 500;
  transition: color 0.2s;
}

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

.nav-cta {
  padding: 8px 18px;
  background: var(--accent);
  color: #fff;
  font-size: 13px;
  font-weight: 600;
  border-radius: var(--radius-sm);
  text-decoration: none;
  transition: background 0.2s, transform 0.15s;
}

.nav-cta:hover {
  background: var(--accent-dark);
  transform: translateY(-1px);
}

/* ========================================
   Hero
   ======================================== */

.hero {
  position: relative;
  padding: 160px 24px 100px;
  text-align: center;
  overflow: hidden;
  border-bottom: 1px solid var(--border);
}

.hero-container {
  position: relative;
  z-index: 2;
  max-width: 800px;
  margin: 0 auto;
}

.hero-label {
  display: inline-block;
  font-size: 13px;
  font-weight: 600;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--accent-light);
  margin-bottom: 20px;
  padding: 6px 14px;
  border: 1px solid var(--accent);
  border-radius: 100px;
  background: rgba(139, 92, 246, 0.08);
}

.hero-title {
  font-size: clamp(40px, 6vw, 64px);
  font-weight: 800;
  line-height: 1.1;
  letter-spacing: -0.03em;
  margin-bottom: 24px;
  background: linear-gradient(135deg, #fff 0%, #c4b5fd 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero-subtitle {
  font-size: 18px;
  color: var(--text-secondary);
  max-width: 640px;
  margin: 0 auto 40px;
  line-height: 1.7;
}

.hero-subtitle strong {
  color: var(--text-primary);
  font-weight: 600;
}

.hero-cta-group {
  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 {
  text-align: center;
}

.stat-number {
  display: block;
  font-size: 32px;
  font-weight: 800;
  color: var(--text-primary);
  line-height: 1.2;
}

.stat-label {
  display: block;
  font-size: 13px;
  font-weight: 500;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.06em;
  margin-top: 4px;
}

.hero-glow {
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  width: 800px;
  height: 400px;
  background: radial-gradient(ellipse, var(--accent-glow) 0%, transparent 70%);
  pointer-events: none;
  z-index: 1;
}

/* ========================================
   Buttons
   ======================================== */

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 14px 28px;
  font-size: 15px;
  font-weight: 600;
  border-radius: var(--radius-sm);
  text-decoration: none;
  cursor: pointer;
  transition: all 0.2s;
  border: none;
}

.btn-primary {
  background: var(--accent);
  color: #fff;
  box-shadow: 0 4px 20px rgba(139, 92, 246, 0.3);
}

.btn-primary:hover {
  background: var(--accent-dark);
  transform: translateY(-2px);
  box-shadow: 0 8px 30px rgba(139, 92, 246, 0.4);
}

.btn-secondary {
  background: var(--bg-tertiary);
  color: var(--text-primary);
  border: 1px solid var(--border);
}

.btn-secondary:hover {
  background: var(--border);
  border-color: var(--border-hover);
  transform: translateY(-2px);
}

/* ========================================
   Sections
   ======================================== */

.section {
  padding: 100px 24px;
}

.section-container {
  max-width: var(--max-width);
  margin: 0 auto;
}

.section-dark {
  background: var(--bg-primary);
}

.section-alt {
  background: var(--bg-secondary);
  border-top: 1px solid var(--border);
  border-bottom: 1px solid var(--border);
}

.section-cta {
  background: var(--bg-secondary);
  text-align: center;
  border-top: 1px solid var(--border);
}

.section-label {
  font-size: 12px;
  font-weight: 700;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--accent-light);
  margin-bottom: 16px;
}

.section-title {
  font-size: clamp(28px, 4vw, 40px);
  font-weight: 800;
  letter-spacing: -0.02em;
  margin-bottom: 16px;
  line-height: 1.2;
}

.section-desc {
  font-size: 17px;
  color: var(--text-secondary);
  max-width: 680px;
  line-height: 1.7;
  margin-bottom: 56px;
}

.section-cta .section-desc {
  margin-left: auto;
  margin-right: auto;
}

/* ========================================
   Features Grid
   ======================================== */

.features-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: 20px;
}

.feature-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 28px;
  transition: border-color 0.2s, transform 0.2s;
}

.feature-card:hover {
  border-color: var(--border-hover);
  transform: translateY(-2px);
}

.feature-icon {
  width: 48px;
  height: 48px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: rgba(139, 92, 246, 0.1);
  border-radius: var(--radius-sm);
  color: var(--accent-light);
  margin-bottom: 18px;
}

.feature-card h3 {
  font-size: 17px;
  font-weight: 700;
  margin-bottom: 10px;
  color: var(--text-primary);
}

.feature-card p {
  font-size: 14px;
  color: var(--text-secondary);
  line-height: 1.65;
}

.feature-card strong {
  color: var(--text-primary);
  font-weight: 600;
}

/* ========================================
   How It Works — Loop
   ======================================== */

.loop-diagram {
  display: flex;
  align-items: flex-start;
  justify-content: center;
  gap: 8px;
  flex-wrap: wrap;
  margin-bottom: 80px;
  padding: 32px;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
}

.loop-step {
  flex: 1;
  min-width: 120px;
  max-width: 160px;
  text-align: center;
}

.loop-badge {
  width: 36px;
  height: 36px;
  border-radius: 50%;
  background: var(--accent);
  color: #fff;
  font-size: 14px;
  font-weight: 700;
  display: flex;
  align-items: center;
  justify-content: center;
  margin: 0 auto 12px;
}

.loop-step h4 {
  font-size: 14px;
  font-weight: 600;
  margin-bottom: 6px;
  color: var(--text-primary);
}

.loop-step p {
  font-size: 12px;
  color: var(--text-muted);
  line-height: 1.5;
}

.loop-arrow {
  color: var(--accent-light);
  font-size: 20px;
  font-weight: 700;
  padding-top: 6px;
  flex-shrink: 0;
}

/* ========================================
   Knowledge Model
   ======================================== */

.knowledge-model {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 48px;
  align-items: start;
}

.km-text h3 {
  font-size: 24px;
  font-weight: 700;
  margin-bottom: 16px;
}

.km-text p {
  font-size: 15px;
  color: var(--text-secondary);
  line-height: 1.7;
  margin-bottom: 14px;
}

.km-text strong {
  color: var(--text-primary);
}

.km-code pre {
  background: var(--bg-primary);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 24px;
  font-family: 'SF Mono', Monaco, 'Cascadia Code', monospace;
  font-size: 13px;
  line-height: 1.6;
  color: var(--text-secondary);
  overflow-x: auto;
}

.km-code code {
  font-family: inherit;
}

/* ========================================
   Skills Table
   ======================================== */

.skills-table {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: 28px;
}

.skill-category {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 24px;
}

.skill-category h4 {
  font-size: 14px;
  font-weight: 700;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  color: var(--accent-light);
  margin-bottom: 16px;
  padding-bottom: 12px;
  border-bottom: 1px solid var(--border);
}

.skill-category ul {
  list-style: none;
}

.skill-category li {
  font-size: 13px;
  color: var(--text-secondary);
  line-height: 1.6;
  margin-bottom: 10px;
  padding-left: 16px;
  position: relative;
}

.skill-category li::before {
  content: "";
  position: absolute;
  left: 0;
  top: 8px;
  width: 6px;
  height: 6px;
  background: var(--accent);
  border-radius: 50%;
}

.skill-category strong {
  color: var(--text-primary);
  font-weight: 600;
}

/* ========================================
   Architecture
   ======================================== */

.arch-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 20px;
  margin-bottom: 64px;
}

.arch-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 28px;
}

.arch-card h4 {
  font-size: 16px;
  font-weight: 700;
  margin-bottom: 10px;
  color: var(--text-primary);
}

.arch-card p {
  font-size: 14px;
  color: var(--text-secondary);
  line-height: 1.65;
}

.arch-card strong {
  color: var(--text-primary);
  font-weight: 600;
}

.benchmark h3 {
  font-size: 24px;
  font-weight: 700;
  margin-bottom: 12px;
}

.benchmark > p {
  font-size: 15px;
  color: var(--text-secondary);
  line-height: 1.7;
  margin-bottom: 28px;
  max-width: 680px;
}

.benchmark-table {
  overflow-x: auto;
}

.benchmark-table table {
  width: 100%;
  border-collapse: collapse;
  font-size: 14px;
}

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

.benchmark-table th {
  font-weight: 600;
  color: var(--text-muted);
  font-size: 12px;
  text-transform: uppercase;
  letter-spacing: 0.06em;
}

.benchmark-table td {
  color: var(--text-secondary);
}

.benchmark-table td strong {
  color: var(--text-primary);
}

.delta {
  color: var(--green);
  font-weight: 600;
}

/* ========================================
   Install Code Block
   ======================================== */

.install-code {
  max-width: 720px;
  margin: 0 auto 40px;
}

.install-code pre {
  background: var(--bg-primary);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 24px 28px;
  font-family: 'SF Mono', Monaco, 'Cascadia Code', monospace;
  font-size: 13px;
  line-height: 1.7;
  color: var(--text-secondary);
  overflow-x: auto;
  text-align: left;
}

.install-code code {
  font-family: inherit;
}

/* ========================================
   FAQ
   ======================================== */

.faq-list {
  max-width: 760px;
}

.faq-item {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  margin-bottom: 12px;
  overflow: hidden;
}

.faq-item summary {
  padding: 20px 24px;
  font-size: 15px;
  font-weight: 600;
  color: var(--text-primary);
  cursor: pointer;
  list-style: none;
  display: flex;
  justify-content: space-between;
  align-items: center;
  transition: background 0.2s;
}

.faq-item summary:hover {
  background: rgba(255,255,255,0.02);
}

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

.faq-item summary::after {
  content: "+";
  font-size: 20px;
  font-weight: 400;
  color: var(--accent-light);
  transition: transform 0.2s;
}

.faq-item[open] summary::after {
  content: "−";
}

.faq-item p {
  padding: 0 24px 20px;
  font-size: 14px;
  color: var(--text-secondary);
  line-height: 1.7;
}

.faq-item code {
  background: var(--bg-tertiary);
  padding: 2px 6px;
  border-radius: 4px;
  font-family: 'SF Mono', Monaco, monospace;
  font-size: 12px;
  color: var(--accent-light);
}

/* ========================================
   Footer
   ======================================== */

.footer {
  background: var(--bg-primary);
  border-top: 1px solid var(--border);
  padding: 64px 24px 32px;
}

.footer-container {
  max-width: var(--max-width);
  margin: 0 auto;
  display: grid;
  grid-template-columns: 1fr 2fr;
  gap: 48px;
}

.footer-brand img {
  display: block;
  height: 24px;
  width: auto;
  margin-bottom: 14px;
}

.footer-brand p {
  font-size: 14px;
  color: var(--text-muted);
  max-width: 280px;
  line-height: 1.6;
}

.footer-links {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 32px;
}

.footer-col h4 {
  font-size: 12px;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--text-muted);
  margin-bottom: 16px;
}

.footer-col a {
  display: block;
  font-size: 14px;
  color: var(--text-secondary);
  text-decoration: none;
  margin-bottom: 10px;
  transition: color 0.2s;
}

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

.footer-bottom {
  max-width: var(--max-width);
  margin: 48px auto 0;
  padding-top: 24px;
  border-top: 1px solid var(--border);
  text-align: center;
}

.footer-bottom p {
  font-size: 13px;
  color: var(--text-muted);
}

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

@media (max-width: 860px) {
  .nav-links {
    display: none;
  }

  .hero {
    padding: 140px 24px 80px;
  }

  .hero-stats {
    gap: 32px;
  }

  .knowledge-model {
    grid-template-columns: 1fr;
  }

  .loop-diagram {
    flex-direction: column;
    align-items: center;
  }

  .loop-step {
    max-width: none;
    width: 100%;
  }

  .loop-arrow {
    transform: rotate(90deg);
    padding: 4px 0;
  }

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

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

@media (max-width: 480px) {
  .hero-stats {
    gap: 24px;
  }

  .stat-number {
    font-size: 26px;
  }

  .features-grid,
  .skills-table {
    grid-template-columns: 1fr;
  }

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

  .btn {
    width: 100%;
  }
}