:root {
  --primary: #2c6fbb;
  --light: #f8f9fa;
  --dark: #212529;
  --gray: #6c757d;
  --border: #dee2e6;
}
* { box-sizing: border-box; margin: 0; padding: 0; }
body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  line-height: 1.6;
  color: var(--dark);
  background-color: #fff;
}
.container {
  width: 100%;
  max-width: 960px;
  margin: 0 auto;
  padding: 0 1rem;
}
header {
  background-color: var(--primary);
  color: white;
  padding: 1rem 0;
}
header .container {
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 1rem;
}
header a { color: white; text-decoration: none; font-weight: bold; }
nav ul {
  display: flex;
  list-style: none;
  gap: 1.5rem;
  margin: 0;
  padding: 0;
}
nav a { color: white; text-decoration: none; }
main { padding: 2rem 0; }
footer {
  background-color: var(--light);
  color: var(--gray);
  padding: 1.5rem 0;
  border-top: 1px solid var(--border);
  font-size: 0.9rem;
}
h1, h2, h3 { margin: 1.5rem 0 1rem; }
.card {
  background: var(--light);
  padding: 1.25rem;
  border-radius: 8px;
  margin-bottom: 1rem;
  border: 1px solid var(--border);
}
.btn {
  display: inline-block;
  background-color: var(--primary);
  color: white;
  padding: 0.5rem 1rem;
  text-decoration: none;
  border-radius: 4px;
  font-weight: bold;
  margin-top: 0.5rem;
}
.btn:hover { background-color: #1e5aa8; }
.topic { margin-bottom: 2.5rem; }
.cards-grid {
  display: flex;
  flex-direction: column;
  gap: 1rem;
}
#lang-switch {
  background: white;
  color: var(--primary);
  border: 1px solid white;
  border-radius: 4px;
  padding: 0.25rem 0.5rem;
  font-weight: bold;
}
@media (min-width: 768px) {
  .cards-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
  }
}