Example of customizing weblog via CSS code injection

weblog_code_injection_example.html

<style>
  .main-header a {
    color: blue;
  }

  .main-header a:hover,
  .main-header a:visited {
    color: darkblue;
  }
  
  @media all and (min-width: 800px) {
    .main-header .container{
      display: grid;
      grid-template-columns: 1fr 1fr 1fr 1fr;
      grid-template-rows: 1fr 1fr;
    }
    
    .main-header__logo {
      line-height: 0;
      grid-column-start: 1;
      grid-column-end: 1;
      grid-row-start: 1;
      grid-row-end: span 2;
    }

    .main-header__text-container {
      text-align: left;
      padding-left: 4rem;
      grid-column-start: 2;
      grid-column-end: span 4;
      grid-row-start: 1;
      grid-row-end: 1;
    }
    .main-header nav {
      text-align: left;
      padding-left: 3.55rem;
      grid-column-start: 2;
      grid-column-end: span 4;
      grid-row-start: 2;
      grid-row-end: 2;
    }
  }
</style>