body {
    background: linear-gradient(90deg, rgb(237, 240, 237) 10%, rgb(153, 233, 153) 25%, rgb(91, 216, 79) 75%, rgb(209, 240, 212) 90%);
    width: 100%;
    margin: auto;
    font-family: 'Courier New', Courier, monospace;
    color: black;
    height: 100%;
    overflow: auto;
  }
  
  header {
    text-align: center;
    border-left: dotted;
    border-right: dotted;
    border-top: dotted;
    border-bottom: dotted;
    vertical-align: middle;
    text-align: center;
    height: 100%;
    width: 94%;
    margin-left: 3%;
    margin-right: 3%;
  }
  
  nav, article, aside {
    height: 100%;
    border: none;
  }
  
  nav {
    margin-left: 3%;
    height: 500px;
    width: 15%;
    float: left;
  }
  
  article {
    width: 64%;
    height: 100%;
    float: left;
    overflow: auto;
  }
  
  aside {
    float: left;
    overflow: hidden; /* zmiana na "hidden" */  
    margin-right: 3%;
    width: 15%;
    height: 500px;
    border: none;
    overflow: hidden;
 }

  iframe {
    width: 100%;
    height: 100%;
  }
  
  * {
    box-sizing: border-box;
  }
  
  body > footer {
    border: dotted black;
    margin-left: 3%;
    margin-right: 3%;
    width: 94%;
    height: 100%;
    clear: both;
  }
  
  body > footer, body > nav, body > article {
    padding: 15px;
  }
  
  /* Dodatkowe style */
  body {
    background-attachment: fixed; /* Utrzymuje tło nieruchome */
    background-size: cover; /* Dopasowuje tło do rozmiaru elementu */
  }
  
  header, nav, article, aside, footer {
    background: inherit; /* Odziedzicza tło od elementu body */
  }