matheus.css

ul {
  list-style-type: none;
  margin: 0;
  padding: 0;
  overflow: hidden;
  background-color: #f1f1f1;
}

li {
  float: left;
}

li a {
  display: block;
  color: white;
  text-align: center;
  padding: 14px 16px;
  text-decoration: none;
}

/* Change the link color to #111 (black) on hover */
li a:hover {
  background-color: #111;
}
li a:hover:not(.active) {
  background-color: #111;
}

.active {
  background-color: #4CAF50;
}
h3{
  
  text-transform: uppercase;
  color: #000000;
}