body {
  background: url("stars-2.gif");
  color: black;
  font-family: Verdana;
}
.center {
  padding: 70px 0;
}
.main {
  background: linear-gradient(#6769f5, #a4a6fc);
  padding: 15px 15px;
}
.sidebar {
  background: linear-gradient(#6769f5, #a4a6fc);
  padding: 15px 15px;
  text-align: left;
  height: 480px;
}
.formulas {
  padding: 0 15px;
}
.footer {
  background-color: #6769f5;
}