* {
  margin: 0;
  padding: 0;
}

.center {
  text-align: center;
}

h1 {
  margin: 25px 0;
  text-decoration: underline;
}

p {
  margin: 10px 0;
}

.ball {
  border: 1px solid black;
  border-radius: 100%;
  display: inline-block;
  height: 50px;
  margin: 10px 5px;
  width: 50px;
}

.btn {
  margin: 25px;
}