#code {
    width: 100%;
}

.form-group {
    width: 100%;
}

.parent {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
}

.child {
  flex: 0 0 10%; /* explanation below */
  text-align: center;
  margin: 5px;
}

@media (max-width: 480px) {
  .child {
      flex: 0 0 22%;
  }
}