*, *::after, *::before {
      box-sizing: border-box;
  }

  :root {
    font:1.2em/1.4 Arial, Helvetica, sans-serif;
  }

  body {
    padding: 0;
      margin: 0;
  }

  .container{
      max-width: 80rem;
      margin-inline: auto;
      padding-inline: 1rem;
  }
  header {
    background-color: #333;
    color: #fff;
    border: 5px solid #000;
      display: flex;
      flex-direction: column ;
  }

  header ul {
    list-style: none;
    margin: 0;
    padding: 0;

  }

  header a {
    color: #fff;
    text-decoration: none;
    display: block;
    padding: 0.5em 1em;
    border-top: 1px solid #999;
  }

  header .title {
    font-size: 150%;
    font-style: italic;
    font-weight: bold;
    padding-block: 1em;
      margin-inline: 1em;
  }

  main {
    padding: 0 1em;
  }

  .cards {
    list-style: none;
    margin: 0;
    padding: 0;
  }

  .cards li {
    border: 5px solid #000;
    margin-bottom: 1em;
      display: flex;
      flex-direction: column;
  }

  .cards h2 {
    background-color: #333;
    color: #fff;
    margin: 0;
    padding: 0.5em 1em;
  }

  .cards .inner {
    padding: 0.5em 1em;
  }

  .sidebar {
    background-color: #333;
    border: 5px solid #000;
    padding: 0.5em 1em;
    color: #fff;
  }


  @media (min-width: 640px) {

      header{
          flex-direction: row;
          justify-content: flex-end;
            a{
                  border: none;
            }
            nav {
            display: flex;
            }
            ul{
                display: flex;
                align-items: center;
                padding: 0;
                margin: 0;
                }
      .title{
          display: flex;
          margin-inline-end: auto;
      }
      main {
          display: flex;
      }
      .cards {
          flex-direction: row;
          gap: 5rem;
      }
      }
  }
@media (min-width:640px) {
    .cards{
        display: flex;
        flex-wrap: wrap;
        gap: 1rem;
        li{
            flex: 0 1 16rem;
        }
    }
}
@media (min-width: 640px) {
    main{
        display: flex;
        margin-block-start: 1rem;
        gap: 1rem;
    }
}