:root {
  --bg: #0f172a;
  --fg: #e2e8f0;
  --accent: #38bdf8;
  --card-bg: #1e293b;
  --max-width: 960px;
}

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

html {
  scroll-behavior: smooth;
}

body {
  font-family: system-ui, -apple-system, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  background: var(--bg);
  color: var(--fg);
  line-height: 1.6;
}

.container {
  width: 100%;
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 1.25rem;
}

/* Header / Nav */
.site-header {
  position: sticky;
  top: 0;
  background: rgba(15, 23, 42, 0.85);
  backdrop-filter: blur(8px);
  border-bottom: 1px solid #1e293b;
  z-index: 10;
}

.nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 64px;
}

.brand {
  font-weight: 700;
  font-size: 1.25rem;
  color: var(--fg);
  text-decoration: none;
}

.nav-links {
  list-style: none;
  display: flex;
  gap: 1.5rem;
}

.nav-links a {
  color: var(--fg);
  text-decoration: none;
  opacity: 0.85;
  transition: opacity 0.2s ease;
}

.nav-links a:hover {
  opacity: 1;
  color: var(--accent);
}

.nav-toggle {
  display: none;
  background: none;
  border: none;
  color: var(--fg);
  font-size: 1.5rem;
  cursor: pointer;
}

/* Hero */
.hero {
  padding: 6rem 1.25rem 4rem;
  text-align: center;
}

.hero h1 {
  font-size: clamp(2rem, 5vw, 3.5rem);
  margin-bottom: 1rem;
}

.accent {
  color: var(--accent);
}

.hero p {
  font-size: 1.125rem;
  opacity: 0.85;
  margin-bottom: 2rem;
}

.btn {
  display: inline-block;
  background: var(--accent);
  color: #0f172a;
  font-weight: 600;
  padding: 0.75rem 1.5rem;
  border-radius: 999px;
  text-decoration: none;
  transition: transform 0.2s ease, box-shadow 0.2s ease;
}

.btn:hover {
  transform: translateY(-2px);
  box-shadow: 0 8px 24px rgba(56, 189, 248, 0.35);
}

/* Sections */
section {
  padding: 4rem 0;
}

h2 {
  font-size: clamp(1.5rem, 3vw, 2.25rem);
  margin-bottom: 1rem;
}

/* Cards */
.cards {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 1.5rem;
  margin-top: 2rem;
}

.card {
  background: var(--card-bg);
  border: 1px solid #334155;
  border-radius: 12px;
  padding: 1.5rem;
  transition: transform 0.2s ease;
}

.card:hover {
  transform: translateY(-4px);
}

.card h3 {
  color: var(--accent);
  margin-bottom: 0.5rem;
}

/* Footer */
.site-footer {
  border-top: 1px solid #1e293b;
  padding: 2rem 0;
  text-align: center;
  opacity: 0.7;
  font-size: 0.9rem;
}

/* Responsive nav */
@media (max-width: 640px) {
  .nav-toggle {
    display: block;
  }

  .nav-links {
    position: absolute;
    top: 64px;
    right: 0;
    left: 0;
    flex-direction: column;
    gap: 0;
    background: var(--bg);
    border-bottom: 1px solid #1e293b;
    max-height: 0;
    overflow: hidden;
    transition: max-height 0.25s ease;
  }

  .nav-links.open {
    max-height: 240px;
  }

  .nav-links li {
    padding: 0.75rem 1.25rem;
    border-top: 1px solid #1e293b;
  }
}