:root {
  --color-primary: #222;
  --color-secondary: #666;
  --color-accent: #0066cc;
  --color-bg: #ffffff;
  --color-bg-alt: #f8f9fa;
  --color-border: #e5e5e5;
  --spacing-xs: 0.5rem;
  --spacing-sm: 1rem;
  --spacing-md: 2rem;
  --spacing-lg: 4rem;
  --spacing-xl: 6rem;
  --border-radius: 8px;
  --max-width: 1200px;
  --transition: all 0.3s ease;
}

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

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Oxygen,
    Ubuntu, Cantarell, sans-serif;
  line-height: 1.6;
  color: var(--color-primary);
  background: var(--color-bg);
}

/* Typography */
h1,
h2,
h3,
h4,
h5,
h6 {
  font-weight: 600;
  line-height: 1.2;
  margin-bottom: var(--spacing-sm);
}

h1 {
  font-size: clamp(2rem, 5vw, 3rem);
}
h2 {
  font-size: clamp(1.5rem, 4vw, 2.5rem);
}
h3 {
  font-size: clamp(1.25rem, 3vw, 1.75rem);
}

p {
  margin-bottom: var(--spacing-sm);
  color: var(--color-secondary);
}

a {
  color: var(--color-accent);
  text-decoration: none;
  transition: var(--transition);
}

a:hover {
  opacity: 0.8;
}

/* Layout */
.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 var(--spacing-md);
}

section {
  margin: var(--spacing-lg) 0;
}

/* Navigation */
nav {
  background: var(--color-bg);
  border-bottom: 1px solid var(--color-border);
  padding: var(--spacing-sm) 0;
  position: sticky;
  top: 0;
  z-index: 100;
}

nav ul {
  list-style: none;
  display: flex;
  gap: var(--spacing-md);
  align-items: center;
}

nav a {
  color: var(--color-primary);
  font-weight: 500;
  padding: var(--spacing-xs) var(--spacing-sm);
  border-radius: var(--border-radius);
}

nav a:hover,
nav a.active {
  background: var(--color-bg-alt);
}

/* Footer */
footer {
  margin-top: var(--spacing-xl);
  padding: var(--spacing-lg) 0;
  border-top: 1px solid var(--color-border);
  text-align: center;
  color: var(--color-secondary);
}

/* Components */
.btn {
  display: inline-block;
  padding: 0.75rem 2rem;
  background: var(--color-primary);
  color: white;
  border-radius: var(--border-radius);
  font-weight: 500;
  transition: var(--transition);
  border: none;
  cursor: pointer;
}

.btn:hover {
  background: var(--color-accent);
  transform: translateY(-2px);
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.15);
}

.card {
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--border-radius);
  padding: var(--spacing-md);
  transition: var(--transition);
}

/* Grid */
.grid {
  display: grid;
  gap: var(--spacing-md);
}

.grid-2 {
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
}
.grid-3 {
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
}

/* Responsive */
@media (max-width: 768px) {
  :root {
    --spacing-lg: 3rem;
    --spacing-xl: 4rem;
  }

  nav ul {
    flex-wrap: wrap;
    gap: var(--spacing-sm);
  }
}