*{
    padding: 0px;
    margin: 0px;
    box-sizing: border-box;
}

header{
  background-color: aliceblue;
}
nav{
  background-color: antiquewhite;
}
main{
  background-color: lightgreen;
  min-height: 400px;
}
details{
  background-color: cadetblue;
}
details > summary{
  background-color: lightgrey;
  list-style-type: none;
  display: flex;
  justify-content: space-between;
}
details > summary::after{
  content: "+";
  font-weight: 700px;
  font-size: x-large;
}
details[open] > summary::after{
  content: "-";
  font-weight: 700px;
  font-size: x-large;
}

/* Add a black background color to the top navigation */
.topnav {
  background-color: #333;
  overflow: hidden;
}

/* Style the links inside the navigation bar */
.topnav a {
  float: left;
  color: #f2f2f2;
  text-align: center;
  padding: 14px 16px;
  text-decoration: none;
  font-size: 17px;
}

/* Change the color of links on hover */
.topnav a:hover {
  background-color: #ddd;
  color: black;
}

/* Add a color to the active/current link */
.topnav a.active {
  background-color: #04AA6D;
  color: white;
}

footer{
  background-color: beige;
}