body {
  margin: 0;
  padding: 0;
  background: #273261;

}

h2, p {
  margin: 10px;
}

ul {
  list-style-type: none;
  margin: 0;
  padding: 0;
  overflow: hidden;
  background-color: #333333;
}

ul li {
  float: left;
}

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

ul li a:hover {
  background-color: #111111;
}
ul li a.active {
  background-color: #04AA6D;
}

.center {
  display: block;
  margin-left: auto;
  margin-right: auto;
  width: 50%;
}

      .box {
            width: 400px;
            height: 300px;
            background-color: rgb(11, 19, 21);
            border: 2px solid blue;
            border-radius: 50%;
            
        }