* {
  box-sizing: border-box;
}

:root {
  --light: #F2E4D0;
  --bright: #FFF5A8;
  --medium: #00565B;
  --dark: #3A4A1E;
}

 body {
  font-family: arial;
    margin: 0;
  padding: 0;
}
.header {
  display: flex;
  color: var(--light);
  background-color: var(--dark);
  justify-content: center;
}

.header a {
  color: var(--light);
  text-decoration: none;
}

.topnav {
  margin:0;
  padding:0;
  display: flex;
  color: var(--light);
  background-color: var(--light);
  justify-content: center;
}

.topnav ul{
  list-style-type: none;
  margin: 0;
  padding: 0;
  background-color: var(--light);
  display: flex;
}

.topnav li a {
  display: block;
  color: var(--dark);
  text-decoration: none;
  padding: 14px 16px;
  white-space: nowrap;
  text-overflow: ellipsis;
  overflow: hidden;
  max-width: 200px;
  max-height: 50px;
}

.topnav li a:hover {
  background-color: var(--bright);
}


.flexbox {
  display:flex;
  flex-wrap:wrap;
}
.flexbox > * {
  width:100%;
  padding:1rem;
}

/* tablet breakpoint */
@media (min-width:768px) {
  .flexbox > .left-sidebar,
  .flexbox > .right-sidebar {
    width:50%;
  }
}

/* desktop breakpoint */
@media (min-width:1024px) {
  .flexbox > .header {
    order:-3; /* header first */
  }
  .flexbox > .topnav {
    order:-2; /* topnav second */
  }
  .flexbox > .left-sidebar {
    /* left sidebar third (second in second row) */
    order:-1;    
  }
  .flexbox > .main-content {
    width:50%;
  }
  .flexbox > .left-sidebar,
  .flexbox > .right-sidebar {
    width:25%;
  }
}