/* ===== CSS Custom Properties ===== */
:root {
  --bg: #f9fafb;
  --surface: #ffffff;
  --surface-alt: #f3f4f6;
  --border: #e5e7eb;
  --text: #111827;
  --text-secondary: #374151;
  --text-muted: #9ca3af;
  --primary: #4f46e5;
  --primary-hover: #4338ca;
  --primary-text: #ffffff;
  --radius: 0.75rem;
  --shadow: 0 1px 3px rgba(0,0,0,0.1), 0 1px 2px rgba(0,0,0,0.06);
  --shadow-md: 0 4px 6px rgba(0,0,0,0.07), 0 2px 4px rgba(0,0,0,0.06);
  --transition: 0.2s ease;
}

[data-theme="dark"] {
  --bg: #111827;
  --surface: #1f2937;
  --surface-alt: #374151;
  --border: #374151;
  --text: #f3f4f6;
  --text-secondary: #d1d5db;
  --text-muted: #6b7280;
}

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

html { scroll-behavior: smooth; }

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.6;
  transition: background var(--transition), color var(--transition);
}

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

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

/* ===== Layout ===== */
.container {
  max-width: 1100px;
  margin: 0 auto;
  padding: 0 1.25rem;
}

section { padding: 4rem 0; }

/* ===== Header / Nav ===== */
header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: var(--surface);
  border-bottom: 1px solid var(--border);
  transition: background var(--transition), border-color var(--transition);
}

.nav {
  display: flex;
  align-items: center;
  gap: 1.5rem;
  padding: 0.875rem 0;
}

.nav-logo {
  display: flex;
  align-items: center;
  flex-shrink: 0;
}

.nav-logo img {
  height: 36px;
  width: auto;
}

.nav-links {
  display: flex;
  align-items: center;
  gap: 1.25rem;
  margin-left: auto;
  list-style: none;
}

.nav-links a {
  color: var(--text-secondary);
  font-size: 0.9375rem;
  font-weight: 500;
  transition: color var(--transition);
}

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

.nav-controls {
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

.lang-select {
  background: var(--surface-alt);
  border: 1px solid var(--border);
  color: var(--text-secondary);
  font-size: 0.875rem;
  padding: 0.375rem 0.625rem;
  border-radius: 0.5rem;
  cursor: pointer;
  transition: border-color var(--transition), background var(--transition);
}

.lang-select:hover { border-color: var(--primary); }

.btn-icon {
  background: var(--surface-alt);
  border: 1px solid var(--border);
  color: var(--text-secondary);
  width: 36px;
  height: 36px;
  border-radius: 0.5rem;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1rem;
  transition: background var(--transition), border-color var(--transition);
}

.btn-icon:hover { background: var(--border); }

/* ===== Buttons ===== */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  padding: 0.75rem 1.5rem;
  border-radius: 0.625rem;
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  border: none;
  transition: background var(--transition), transform 0.1s ease, box-shadow var(--transition);
}

.btn-primary {
  background: var(--primary);
  color: var(--primary-text);
  box-shadow: 0 2px 8px rgba(79,70,229,0.35);
}

.btn-primary:hover {
  background: var(--primary-hover);
  color: var(--primary-text);
  transform: translateY(-1px);
  box-shadow: 0 4px 14px rgba(79,70,229,0.45);
}

.btn-outline {
  background: transparent;
  color: var(--primary);
  border: 2px solid var(--primary);
}

.btn-outline:hover {
  background: var(--primary);
  color: var(--primary-text);
}

/* ===== Hero ===== */
.hero {
  text-align: center;
  padding: 5rem 0 4rem;
  background: var(--bg);
}

.hero h1 {
  font-size: clamp(2rem, 5vw, 3.25rem);
  font-weight: 800;
  line-height: 1.15;
  letter-spacing: -0.02em;
  color: var(--text);
  margin-bottom: 1.25rem;
}

.hero p {
  font-size: clamp(1rem, 2.5vw, 1.25rem);
  color: var(--text-secondary);
  max-width: 600px;
  margin: 0 auto 2rem;
}

/* ===== Features ===== */
.features {
  background: var(--surface-alt);
}

.features h2,
.how-it-works h2,
.cta-section h2 {
  font-size: clamp(1.5rem, 3.5vw, 2.25rem);
  font-weight: 700;
  text-align: center;
  margin-bottom: 2.5rem;
  color: var(--text);
}

.features-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 1.5rem;
}

.feature-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.75rem 1.5rem;
  box-shadow: var(--shadow);
  transition: transform var(--transition), box-shadow var(--transition);
}

.feature-card:hover {
  transform: translateY(-3px);
  box-shadow: var(--shadow-md);
}

.feature-icon {
  font-size: 2rem;
  margin-bottom: 0.875rem;
}

.feature-card h3 {
  font-size: 1.0625rem;
  font-weight: 700;
  margin-bottom: 0.5rem;
  color: var(--text);
}

.feature-card p {
  font-size: 0.9375rem;
  color: var(--text-secondary);
  line-height: 1.55;
}

/* ===== How It Works ===== */
.steps-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 2rem;
  position: relative;
}

.step {
  text-align: center;
  padding: 0 1rem;
}

.step-num {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 48px;
  height: 48px;
  border-radius: 50%;
  background: var(--primary);
  color: #fff;
  font-size: 1.25rem;
  font-weight: 700;
  margin: 0 auto 1rem;
}

.step h3 {
  font-size: 1.0625rem;
  font-weight: 700;
  margin-bottom: 0.5rem;
  color: var(--text);
}

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

/* ===== CTA Section ===== */
.cta-section {
  background: var(--surface-alt);
  text-align: center;
}

.cta-section p {
  font-size: 1.0625rem;
  color: var(--text-secondary);
  margin-bottom: 1.75rem;
  max-width: 480px;
  margin-left: auto;
  margin-right: auto;
}

/* ===== Footer ===== */
footer {
  background: var(--surface);
  border-top: 1px solid var(--border);
  padding: 1.75rem 0;
}

.footer-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 1rem;
}

.footer-copyright {
  font-size: 0.875rem;
  color: var(--text-muted);
}

.footer-links {
  display: flex;
  gap: 1.25rem;
  list-style: none;
}

.footer-links a {
  font-size: 0.875rem;
  color: var(--text-muted);
  transition: color var(--transition);
}

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

/* ===== Visually Hidden ===== */
.visually-hidden {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  overflow: hidden;
  clip: rect(0,0,0,0);
  white-space: nowrap;
  border: 0;
}

/* ===== Mobile Nav ===== */
.nav-hamburger {
  display: none;
  background: var(--surface-alt);
  border: 1px solid var(--border);
  color: var(--text);
  width: 36px;
  height: 36px;
  border-radius: 0.5rem;
  cursor: pointer;
  font-size: 1.25rem;
  align-items: center;
  justify-content: center;
  transition: background var(--transition);
}

.nav-hamburger:hover { background: var(--border); }

.nav-mobile-menu {
  display: none;
  flex-direction: column;
  background: var(--surface);
  border-bottom: 1px solid var(--border);
  padding: 0.75rem 1.25rem 1rem;
  gap: 0.5rem;
}

.nav-mobile-menu a {
  display: block;
  padding: 0.5rem 0;
  color: var(--text-secondary);
  font-size: 1rem;
  font-weight: 500;
  border-bottom: 1px solid var(--border);
  transition: color var(--transition);
}

.nav-mobile-menu a:last-child { border-bottom: none; }
.nav-mobile-menu a:hover { color: var(--primary); }
.nav-mobile-menu.open { display: flex; }

/* ===== Responsive ===== */
@media (max-width: 640px) {
  .nav-links { display: none; }
  .nav-hamburger { display: flex; }
  .nav { gap: 0.75rem; }
  section { padding: 2.5rem 0; }
  .hero { padding: 3rem 0 2.5rem; }
  .footer-inner { flex-direction: column; align-items: flex-start; }
}