.wrapper {
  width: 900px;
  max-width: 100%;
  margin: auto;
}

form.multi-form {
  padding: 20px;
}
form.multi-form fieldset:not(.active) {
  display: none;
}
form.multi-form fieldset.active:first-of-type ~ .buttons .prev,
form.multi-form fieldset.active:first-of-type ~ .buttons .submit {
  display: none;
}
form.multi-form fieldset.active:not(:last-of-type) ~ .buttons .submit {
  display: none;
}
form.multi-form fieldset.active:last-of-type ~ .buttons .next {
  display: none;
}