/* ============================================
   ThinkingKit Design System
   Editorial refined aesthetic
   ============================================ */

/* --- Fonts --- */
@import url('https://fonts.googleapis.com/css2?family=Newsreader:ital,opsz,wght@0,6..72,300;0,6..72,400;0,6..72,500;0,6..72,600;1,6..72,400&family=DM+Sans:ital,wght@0,400;0,500;0,600;0,700;1,400&family=JetBrains+Mono:wght@400;500&display=swap');

/* --- Variables --- */
:root {
  --color-bg: #090a0c;
  --color-bg-elevated: #111318;
  --color-bg-card: #15171c;
  --color-bg-card-hover: #1a1d24;
  --color-surface: #1e2028;
  --color-border: #2a2d38;
  --color-border-subtle: #1e2028;

  --color-text: #e8e9ed;
  --color-text-secondary: #9ea1ad;
  --color-text-muted: #6b6f7e;

  --color-amber: #f59e0b;
  --color-amber-light: #fbbf24;
  --color-amber-dim: #b47708;
  --color-amber-glow: rgba(245, 158, 11, 0.08);
  --color-amber-glow-strong: rgba(245, 158, 11, 0.15);

  --color-teal: #14b8a6;
  --color-teal-dim: #0f9688;

  --color-red: #ef4444;
  --color-green: #22c55e;
  --color-blue: #3b82f6;

  --font-display: 'Newsreader', Georgia, serif;
  --font-body: 'DM Sans', -apple-system, sans-serif;
  --font-mono: 'JetBrains Mono', monospace;

  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 16px;
  --radius-xl: 24px;

  --space-xs: 0.25rem;
  --space-sm: 0.5rem;
  --space-md: 1rem;
  --space-lg: 1.5rem;
  --space-xl: 2.5rem;
  --space-2xl: 4rem;
  --space-3xl: 6rem;

  --max-width: 1200px;
  --max-width-content: 720px;

  --transition-fast: 150ms ease;
  --transition-base: 250ms ease;
  --transition-slow: 400ms cubic-bezier(0.16, 1, 0.3, 1);
}

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

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

body {
  font-family: var(--font-body);
  background: var(--color-bg);
  color: var(--color-text);
  line-height: 1.7;
  min-height: 100vh;
}

img { max-width: 100%; height: auto; display: block; }
a { color: var(--color-amber); text-decoration: none; transition: color var(--transition-fast); }
a:hover { color: var(--color-amber-light); }

/* --- Typography --- */
h1, h2, h3, h4 {
  font-family: var(--font-display);
  font-weight: 500;
  line-height: 1.2;
  color: var(--color-text);
  letter-spacing: -0.01em;
}

h1 { font-size: clamp(2.2rem, 5vw, 3.5rem); }
h2 { font-size: clamp(1.6rem, 3.5vw, 2.2rem); margin-top: var(--space-2xl); margin-bottom: var(--space-lg); }
h3 { font-size: clamp(1.2rem, 2.5vw, 1.5rem); margin-top: var(--space-xl); margin-bottom: var(--space-md); }

p { margin-bottom: var(--space-md); color: var(--color-text-secondary); }

.label {
  font-family: var(--font-body);
  font-size: 0.7rem;
  font-weight: 600;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--color-amber);
}

code, pre {
  font-family: var(--font-mono);
  font-size: 0.85em;
}

/* --- Layout --- */
.wrapper {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 var(--space-lg);
}

.content-wrapper {
  max-width: var(--max-width-content);
  margin: 0 auto;
  padding: 0 var(--space-lg);
}

/* --- Navigation --- */
.site-nav {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 100;
  padding: var(--space-md) var(--space-lg);
  background: rgba(9, 10, 12, 0.85);
  backdrop-filter: blur(20px) saturate(180%);
  -webkit-backdrop-filter: blur(20px) saturate(180%);
  border-bottom: 1px solid var(--color-border-subtle);
  transition: background var(--transition-base);
}

.site-nav .nav-inner {
  max-width: var(--max-width);
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.site-nav .nav-brand {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  color: var(--color-text);
  font-family: var(--font-body);
  font-weight: 700;
  font-size: 1.1rem;
  letter-spacing: -0.02em;
}

.site-nav .nav-brand svg {
  width: 28px;
  height: 28px;
}

.site-nav .nav-links {
  display: flex;
  align-items: center;
  gap: var(--space-xl);
  list-style: none;
}

.site-nav .nav-links a {
  color: var(--color-text-secondary);
  font-size: 0.85rem;
  font-weight: 500;
  letter-spacing: 0.02em;
  transition: color var(--transition-fast);
  position: relative;
}

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

.site-nav .nav-links a.active {
  color: var(--color-amber);
}

/* Mobile nav toggle */
.nav-toggle { display: none; background: none; border: none; color: var(--color-text); cursor: pointer; padding: var(--space-sm); }

@media (max-width: 768px) {
  .nav-toggle { display: block; }
  .site-nav .nav-links {
    display: none;
    position: absolute;
    top: 100%;
    left: 0;
    right: 0;
    flex-direction: column;
    background: var(--color-bg-elevated);
    border-bottom: 1px solid var(--color-border);
    padding: var(--space-lg);
    gap: var(--space-lg);
  }
  .site-nav .nav-links.open { display: flex; }
}

/* --- Hero (Homepage) --- */
.hero {
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  text-align: center;
  padding: var(--space-3xl) var(--space-lg);
  position: relative;
  overflow: hidden;
}

.hero::before {
  content: '';
  position: absolute;
  top: -30%;
  left: 50%;
  transform: translateX(-50%);
  width: 800px;
  height: 800px;
  background: radial-gradient(circle, var(--color-amber-glow) 0%, transparent 70%);
  pointer-events: none;
}

.hero-content {
  position: relative;
  z-index: 1;
  max-width: 700px;
}

.hero .logo-mark {
  width: 72px;
  height: 72px;
  margin: 0 auto var(--space-xl);
  opacity: 0;
  animation: fadeUp 0.8s ease forwards;
}

.hero h1 {
  font-size: clamp(2.8rem, 6vw, 4.5rem);
  font-weight: 400;
  letter-spacing: -0.03em;
  margin-bottom: var(--space-lg);
  opacity: 0;
  animation: fadeUp 0.8s ease 0.15s forwards;
}

.hero h1 em {
  font-style: italic;
  color: var(--color-amber);
}

.hero .hero-sub {
  font-size: clamp(1rem, 2vw, 1.25rem);
  color: var(--color-text-secondary);
  max-width: 540px;
  margin: 0 auto var(--space-xl);
  line-height: 1.8;
  opacity: 0;
  animation: fadeUp 0.8s ease 0.3s forwards;
}

.hero .hero-cta {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-md);
  flex-wrap: wrap;
  opacity: 0;
  animation: fadeUp 0.8s ease 0.45s forwards;
}

@keyframes fadeUp {
  from { opacity: 0; transform: translateY(20px); }
  to { opacity: 1; transform: translateY(0); }
}

/* --- Buttons --- */
.btn {
  display: inline-flex;
  align-items: center;
  gap: var(--space-sm);
  padding: 0.75rem 1.75rem;
  border-radius: var(--radius-md);
  font-family: var(--font-body);
  font-size: 0.9rem;
  font-weight: 600;
  cursor: pointer;
  border: none;
  transition: all var(--transition-base);
  text-decoration: none;
}

.btn-primary {
  background: var(--color-amber);
  color: #0a0a0a;
}

.btn-primary:hover {
  background: var(--color-amber-light);
  color: #0a0a0a;
  transform: translateY(-1px);
  box-shadow: 0 8px 24px rgba(245, 158, 11, 0.25);
}

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

.btn-secondary:hover {
  color: var(--color-text);
  border-color: var(--color-text-muted);
  background: var(--color-bg-card);
}

/* --- Cards --- */
.card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: var(--space-lg);
}

.card {
  background: var(--color-bg-card);
  border: 1px solid var(--color-border-subtle);
  border-radius: var(--radius-lg);
  padding: var(--space-xl);
  transition: all var(--transition-base);
  text-decoration: none;
  color: inherit;
  display: block;
  position: relative;
  overflow: hidden;
}

.card:hover {
  background: var(--color-bg-card-hover);
  border-color: var(--color-border);
  transform: translateY(-2px);
  box-shadow: 0 12px 40px rgba(0, 0, 0, 0.3);
}

.card .card-icon {
  width: 44px;
  height: 44px;
  border-radius: var(--radius-md);
  background: var(--color-amber-glow-strong);
  display: flex;
  align-items: center;
  justify-content: center;
  margin-bottom: var(--space-lg);
  color: var(--color-amber);
  font-size: 1.2rem;
}

.card h3 {
  font-family: var(--font-display);
  font-size: 1.2rem;
  font-weight: 500;
  margin-top: 0;
  margin-bottom: var(--space-sm);
  color: var(--color-text);
}

.card p {
  font-size: 0.9rem;
  color: var(--color-text-muted);
  margin-bottom: 0;
  line-height: 1.6;
}

.card .card-meta {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  margin-top: var(--space-lg);
  flex-wrap: wrap;
}

.card .card-tag {
  font-size: 0.7rem;
  font-weight: 600;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  padding: 0.2rem 0.6rem;
  border-radius: var(--radius-sm);
  background: var(--color-amber-glow);
  color: var(--color-amber);
}

.card .card-tag--teal {
  background: rgba(20, 184, 166, 0.1);
  color: var(--color-teal);
}

/* --- Section styling --- */
.section {
  padding: var(--space-3xl) var(--space-lg);
}

.section-header {
  text-align: center;
  max-width: 600px;
  margin: 0 auto var(--space-2xl);
}

.section-header .label {
  margin-bottom: var(--space-md);
  display: block;
}

.section-header p {
  font-size: 1.05rem;
}

/* --- Model page --- */
.model-header {
  padding: calc(80px + var(--space-3xl)) var(--space-lg) var(--space-2xl);
  text-align: center;
  max-width: 800px;
  margin: 0 auto;
}

.model-header .question-hook {
  font-family: var(--font-display);
  font-size: clamp(1.3rem, 3vw, 1.8rem);
  font-style: italic;
  color: var(--color-amber);
  margin-bottom: var(--space-lg);
  line-height: 1.4;
}

.model-header h1 {
  margin-bottom: var(--space-md);
}

.model-header .one-liner {
  font-size: 1.1rem;
  color: var(--color-text-secondary);
  max-width: 600px;
  margin: 0 auto var(--space-lg);
}

.model-header .model-meta {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-md);
  flex-wrap: wrap;
}

.model-content {
  max-width: var(--max-width-content);
  margin: 0 auto;
  padding: 0 var(--space-lg) var(--space-3xl);
}

.model-content h2 {
  font-size: 1.5rem;
  padding-top: var(--space-xl);
  border-top: 1px solid var(--color-border-subtle);
}

.model-content p {
  font-size: 1.02rem;
  line-height: 1.85;
}

.model-content ul, .model-content ol {
  margin-bottom: var(--space-md);
  padding-left: var(--space-lg);
  color: var(--color-text-secondary);
}

.model-content li {
  margin-bottom: var(--space-sm);
  line-height: 1.7;
}

/* Visual explanation box */
.visual-box {
  background: var(--color-bg-elevated);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: var(--space-xl);
  margin: var(--space-xl) 0;
  text-align: center;
}

.visual-box svg {
  max-width: 100%;
  height: auto;
}

/* Related models */
.related-models {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
  gap: var(--space-md);
  margin-top: var(--space-lg);
}

/* --- Tools page --- */
.tool-embed {
  background: var(--color-bg-card);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: var(--space-xl);
  margin: var(--space-xl) 0;
}

/* --- Filter bar --- */
.filter-bar {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  flex-wrap: wrap;
  margin-bottom: var(--space-xl);
  padding-bottom: var(--space-lg);
  border-bottom: 1px solid var(--color-border-subtle);
}

.filter-btn {
  font-family: var(--font-body);
  font-size: 0.8rem;
  font-weight: 500;
  padding: 0.4rem 1rem;
  border-radius: 100px;
  border: 1px solid var(--color-border);
  background: transparent;
  color: var(--color-text-secondary);
  cursor: pointer;
  transition: all var(--transition-fast);
}

.filter-btn:hover {
  border-color: var(--color-text-muted);
  color: var(--color-text);
}

.filter-btn.active {
  background: var(--color-amber);
  border-color: var(--color-amber);
  color: #0a0a0a;
}

/* --- Feature grid (homepage) --- */
.feature-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--space-lg);
  max-width: var(--max-width);
  margin: 0 auto;
}

@media (max-width: 900px) { .feature-grid { grid-template-columns: repeat(2, 1fr); } }
@media (max-width: 600px) { .feature-grid { grid-template-columns: 1fr; } }

.feature-item {
  padding: var(--space-xl);
  border-radius: var(--radius-lg);
  background: var(--color-bg-card);
  border: 1px solid var(--color-border-subtle);
}

.feature-item .feature-number {
  font-family: var(--font-display);
  font-size: 2rem;
  font-weight: 300;
  color: var(--color-amber-dim);
  margin-bottom: var(--space-md);
  line-height: 1;
}

.feature-item h3 {
  font-size: 1.1rem;
  margin-top: 0;
  margin-bottom: var(--space-sm);
}

.feature-item p {
  font-size: 0.88rem;
  margin-bottom: 0;
}

/* --- Stats row --- */
.stats-row {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-2xl);
  padding: var(--space-2xl) var(--space-lg);
  flex-wrap: wrap;
}

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

.stat-item .stat-number {
  font-family: var(--font-display);
  font-size: 2.5rem;
  font-weight: 400;
  color: var(--color-text);
  letter-spacing: -0.03em;
}

.stat-item .stat-label {
  font-size: 0.8rem;
  color: var(--color-text-muted);
  margin-top: var(--space-xs);
}

/* --- Footer --- */
.site-footer {
  border-top: 1px solid var(--color-border-subtle);
  padding: var(--space-2xl) var(--space-lg);
  text-align: center;
}

.site-footer p {
  font-size: 0.85rem;
  color: var(--color-text-muted);
}

.site-footer a {
  color: var(--color-text-secondary);
}

/* --- Utility --- */
.text-center { text-align: center; }
.mt-xl { margin-top: var(--space-xl); }
.mt-2xl { margin-top: var(--space-2xl); }
.mb-xl { margin-bottom: var(--space-xl); }
.mb-2xl { margin-bottom: var(--space-2xl); }

/* --- Animations --- */
@media (prefers-reduced-motion: no-preference) {
  .animate-in {
    opacity: 0;
    transform: translateY(16px);
    transition: opacity 0.6s ease, transform 0.6s ease;
  }
  .animate-in.visible {
    opacity: 1;
    transform: translateY(0);
  }
}