* { box-sizing: border-box; margin: 0; padding: 0; }
  body { 
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif; 
    background: #f5f5f5; 
    min-height: 100vh;
    display: flex;
    flex-direction: column;
  }
  header { text-align: center; padding: 10px 0; background: #111; }
  header img { height: 60px; width: auto; }
  main { 
    flex: 1; 
    padding: 10px;
  }