Edit in JSFiddle

@import "compass/css3";

.navigation {
  list-style: none;
  margin: 0; 
  
  background-color: #05175C;
  
  display: -webkit-box;
  display: -moz-box;
  display: -ms-flexbox;
  display: -webkit-flex;
  display: flex;
  
  -webkit-flex-flow: row wrap;
  justify-content: flex-start;
}

.navigation a {
  text-decoration: none;
  font-size:18px;
  display: block;
  padding: 1em;
  color: white;
   -webkit-transition-duration: 0.7s; /* Safari */
   transition-duration: 0.7s;
}

.navigation a:hover {
 background-color:#EE0000;
}

.navigation a:active {
 background-color: #2F4F4F;
}

@media all and (max-width: 800px) {
  .navigation {
    justify-content: space-around;
  }
}

@media all and (max-width: 600px) {
  .navigation {
    -webkit-flex-flow: column wrap;
    flex-flow: column wrap;
    padding: 0;
  }
  
  .navigation a { 
    text-align: center; 
    padding: 10px;
    border-top: 1px solid rgba(255,255,255,0.3); 
    border-bottom: 1px solid rgba(0,0,0,0.1); 
  }

  
  .navigation li:last-of-type a {
    border-bottom: none;
  }
}