/* Math Solver – Thoughtlane theme */

:root {
  --primary: #0d6b8a;
  --primary-light: #1493b8;
  --accent: #0ea88c;
  --accent-light: #2dd4bf;
  --bg: #0c1222;
  --surface: #151d2e;
  --surface-elevated: #1e293b;
  --text: #e2e8f0;
  --text-muted: #94a3b8;
  --accent-soft: rgba(14, 168, 140, 0.2);
  --border: rgba(255, 255, 255, 0.08);
  --radius: 8px;
  --radius-lg: 12px;
  --font-sans: 'DM Sans', system-ui, -apple-system, sans-serif;
  --font-serif: 'Fraunces', serif;
  --font-mono: 'JetBrains Mono', ui-monospace, monospace;
  --space: 1.5rem;
  --space-lg: 2.5rem;
  --space-xl: 4rem;
  --max-width: 960px;
}

/* Light theme */
body:not(.dark-theme) {
  --bg: #f8fafc;
  --surface: #ffffff;
  --surface-elevated: #f1f5f9;
  --text: #0f172a;
  --text-muted: #64748b;
  --border: rgba(15, 23, 42, 0.1);
}

*,
*::before,
*::after {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  font-family: var(--font-sans);
  font-size: 1rem;
  line-height: 1.6;
  color: var(--text);
  background: var(--bg);
  -webkit-font-smoothing: antialiased;
  transition: background 0.4s ease, color 0.4s ease;
}

h1, h2, h3 {
  font-family: var(--font-serif);
}

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

/* Header */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(12, 18, 34, 0.72);
  backdrop-filter: blur(20px) saturate(180%);
  -webkit-backdrop-filter: blur(20px) saturate(180%);
  border-bottom: 1px solid var(--border);
  transition: background 0.4s ease;
}

body:not(.dark-theme) .site-header {
  background: rgba(248, 250, 252, 0.72);
}

.site-header .wrap {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding-top: var(--space);
  padding-bottom: var(--space);
}

.header-left {
  display: flex;
  align-items: center;
  gap: var(--space);
}

.logo-back {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  color: var(--text-muted);
  text-decoration: none;
  font-size: 0.9rem;
  font-weight: 500;
  transition: color 0.2s ease;
}

.logo-back:hover {
  color: var(--accent-light);
}

.logo-img {
  height: 56px;
  width: auto;
}

.logo {
  font-weight: 700;
  font-size: 1.25rem;
  color: var(--text);
  text-decoration: none;
  letter-spacing: -0.02em;
}

.logo:hover {
  color: var(--accent-light);
}

.theme-toggle {
  width: 40px;
  height: 40px;
  border-radius: 10px;
  border: 1px solid var(--border);
  background: rgba(14, 168, 140, 0.15);
  color: var(--accent-light);
  cursor: pointer;
  font-size: 1.1rem;
  transition: all 0.2s ease;
}

.theme-toggle:hover {
  background: rgba(14, 168, 140, 0.25);
}

.nav {
  display: flex;
  align-items: center;
  gap: var(--space);
}

.nav a {
  color: var(--text-muted);
  text-decoration: none;
  font-size: 0.9375rem;
  font-weight: 500;
}

.nav a:hover {
  color: var(--accent-light);
}

/* Hero */
.hero {
  padding: var(--space-xl) 0;
  text-align: center;
}

.hero h1 {
  margin: 0 0 var(--space);
  font-size: clamp(2rem, 5vw, 3rem);
  font-weight: 700;
  line-height: 1.2;
  letter-spacing: -0.03em;
  color: var(--text);
}

.hero-lead {
  max-width: 36em;
  margin: 0 auto var(--space-lg);
  font-size: 1.125rem;
  color: var(--text-muted);
}

.hero-cta {
  display: flex;
  gap: var(--space);
  justify-content: center;
  flex-wrap: wrap;
}

/* Buttons */
.btn {
  display: inline-block;
  padding: 0.75rem 1.5rem;
  font-family: var(--font-sans);
  font-size: 0.9375rem;
  font-weight: 600;
  text-decoration: none;
  border-radius: var(--radius);
  transition: background 0.2s, color 0.2s;
}

.btn-primary {
  background: linear-gradient(135deg, var(--primary) 0%, var(--primary-light) 100%);
  color: white;
}

.btn-primary:hover {
  background: linear-gradient(135deg, var(--primary-light) 0%, var(--accent) 100%);
  color: white;
}

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

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

/* Sections */
section {
  padding: var(--space-xl) 0;
}

section:nth-child(even) {
  background: var(--surface);
}

h2 {
  margin: 0 0 var(--space);
  font-size: 1.75rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  color: var(--text);
}

.section-lead {
  margin: 0 0 var(--space-lg);
  font-size: 1.0625rem;
  color: var(--text-muted);
  max-width: 42em;
}

/* Intro */
.intro-text {
  margin: 0 0 var(--space);
  font-size: 1.0625rem;
}

.intro-list {
  margin: 0 0 var(--space);
  padding-left: 1.5em;
}

.intro-list li {
  margin-bottom: 0.5em;
}

.intro-note {
  margin: 0;
  padding: var(--space);
  background: var(--accent-soft);
  border-radius: var(--radius);
  font-size: 0.9375rem;
  color: var(--text-muted);
}

/* Pipeline / How it works */
.pipeline-steps {
  display: grid;
  gap: var(--space-lg);
}

.step {
  display: grid;
  grid-template-columns: auto 1fr;
  gap: var(--space);
  align-items: start;
}

.step-num {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 2.5rem;
  height: 2.5rem;
  background: linear-gradient(135deg, var(--primary) 0%, var(--accent) 100%);
  color: white;
  font-weight: 700;
  font-size: 1rem;
  border-radius: 50%;
  flex-shrink: 0;
}

.step h3 {
  margin: 0 0 0.25em;
  font-size: 1.125rem;
  font-weight: 600;
  color: var(--text);
}

.step p {
  margin: 0;
  font-size: 0.9375rem;
  color: var(--text-muted);
}

.step code {
  font-family: var(--font-mono);
  font-size: 0.875em;
  padding: 0.15em 0.4em;
  background: var(--surface-elevated);
  border-radius: 4px;
  color: var(--accent-light);
}

/* Features */
.feature-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: var(--space);
}

.feature-card {
  padding: var(--space);
  background: rgba(21, 29, 46, 0.5);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  transition: transform 0.35s cubic-bezier(0.4, 0, 0.2, 1), box-shadow 0.35s ease;
}

body:not(.dark-theme) .feature-card {
  background: rgba(255, 255, 255, 0.7);
}

.feature-card:hover {
  transform: translateY(-2px);
  box-shadow: 0 12px 24px rgba(13, 107, 138, 0.15);
}

.feature-card h3 {
  margin: 0 0 0.5em;
  font-size: 1.0625rem;
  font-weight: 600;
  color: var(--text);
}

.feature-card p {
  margin: 0;
  font-size: 0.9375rem;
  color: var(--text-muted);
}

/* Use cases */
.use-case-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
  gap: var(--space);
}

.use-case {
  padding: var(--space);
  background: rgba(21, 29, 46, 0.5);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-radius: var(--radius-lg);
  border-left: 3px solid var(--accent-light);
  transition: transform 0.35s cubic-bezier(0.4, 0, 0.2, 1);
}

body:not(.dark-theme) .use-case {
  background: rgba(255, 255, 255, 0.7);
}

.use-case:hover {
  transform: translateY(-2px);
}

.use-case h3 {
  margin: 0 0 0.5em;
  font-size: 1.0625rem;
  font-weight: 600;
  color: var(--text);
}

.use-case p {
  margin: 0;
  font-size: 0.9375rem;
  color: var(--text-muted);
}

/* Technology */
.tech-list {
  margin: 0;
  padding-left: 1.5em;
}

.tech-list li {
  margin-bottom: 0.75em;
  font-size: 0.9375rem;
  color: var(--text-muted);
}

.tech-list strong {
  color: var(--text);
}

/* CTA */
.cta {
  text-align: center;
}

.cta h2 {
  margin-bottom: 0.5em;
}

.cta p {
  margin: 0 0 var(--space);
  color: var(--text-muted);
}

.cta-links {
  display: flex;
  gap: var(--space);
  justify-content: center;
  flex-wrap: wrap;
  margin-top: var(--space-lg) !important;
}

/* Footer */
.site-footer {
  padding: var(--space-lg) 0;
  border-top: 1px solid var(--border);
}

.site-footer p {
  margin: 0;
  font-size: 0.875rem;
  color: var(--text-muted);
}

.footer-back {
  display: inline-block;
  margin-top: 1rem;
  color: var(--accent-light) !important;
  text-decoration: none;
  font-weight: 500;
}

.footer-back:hover {
  text-decoration: underline;
}

/* Responsive */
@media (max-width: 640px) {
  .site-header .wrap {
    flex-direction: column;
    align-items: flex-start;
    gap: var(--space);
  }

  .nav {
    flex-wrap: wrap;
  }

  .hero-cta {
    flex-direction: column;
  }

  .btn {
    display: block;
    text-align: center;
  }
}