body {
    margin: 0;
    font-family: Arial, sans-serif;
    background: #f7f7f7;
    color: #222;
  }
  
  .topbar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 16px 24px;
    background: white;
    border-bottom: 1px solid #ddd;
  }
  
  nav button {
    margin-left: 8px;
    padding: 8px 14px;
    cursor: pointer;
  }
  
  main {
    max-width: 800px;
    margin: 40px auto;
    padding: 0 20px;
  }
  
  .page {
    display: none;
    background: white;
    padding: 24px;
    border-radius: 12px;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.06);
  }
  
  .page.active {
    display: block;
  }