.center {
  margin: auto;
  width: 50%;
  border: 3px solid green;
  padding: 10px;
}
.rainbow-text {
background: linear-gradient(to right, #ef5350, #f48fb1, #7e57c2, #2196f3, #26c6da, #43a047, #eeff41, #f9a825, #ff5722);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

h1 {
  text-align: center;
}
h4 {
  text-align: center;
}