.wrapper {
  display: flex;  
}
.content-wrapper {
  display: flex;  
  justify-content: space-evenly;
  align-items: center;
  margin-top: 4em;
  margin-bottom: 4em;
}
.sidebar {
  padding-left: 4px;
  position: -webkit-sticky;
  position: sticky;
  top: 0;
  height: 100vh;
  width: 300px;
  overflow-y: auto;  
}
.sidebar a {
  display: block;
}
.caption{
  display: block;
  text-align: center;
}
body { 
  line-height: 1.5;
  font-family: sans-serif; 
}
main {
  overflow-x: auto;
  max-width: 900px;
  margin: auto;
  padding: 1em;
}
header { text-align: center; }
footer { text-align: center; }
nav { margin-bottom: 2em; }
nav a { margin: 0.2em 0; }
.toc-h3 { margin-left: 1em; font-size: 0.9em; }
.toc-h4 { margin-left: 2em; font-size: 0.9em; }
img{  
  display: block;
  margin-left: auto;
  margin-right: auto;
}
li + li{
  margin-top: 1em;
}
@media (max-width:992px){
  .wrapper {
    display: block;
  }
  header {
    min-height: max-content;
  }
  .sidebar{
    column-count: 2;  
    flex-wrap: wrap;
    position: static;
    font-size: 0.9em;
    height: auto;
    width: auto;
  }
  .content-wrapper {
    display: grid;
    justify-content: center;
  }

}