* {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    box-sizing: border-box;
}

.nav-bar {
  width: 100%;
  background-color: #555;
  overflow: auto;
  display: block; 
}

.nav-bar a {
  float: left;
  padding: 12px;
  color: white;
  text-decoration: none;
  font-size: 17px;
  width: 25%; 
  text-align: center;
 
}

.nav-bar a:hover {
  background-color: #0081cb;
}

@media screen and (max-width: 500px) {
  .nav-bar a {
    float: none;
    display: block;
    width: 100%;
    text-align: left; 
  }
}