:root {
  --bg-color: #ffffff;
  --text-color: #000000;
}

body.dark {
  --bg-color: #121212;
  --text-color: #f0f0f0;
}

body {
  background-color: var(--bg-color);
  color: var(--text-color);
  font-family: sans-serif;
  margin: 0;
  padding: 0;
}

header {
  padding: 1rem;
  background: #0077cc;
  color: white;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

nav a, nav button {
  margin: 0 0.5rem;
  color: white;
  text-decoration: none;
  background: none;
  border: none;
  cursor: pointer;
}

main {
  padding: 1rem;
}

.articles img {
  width: 100%;
  max-width: 300px;
}