In a symmetry puzzle, there are multiple copies of the same protein. Players can work on one copy of the protein, called the "monomer" or "main chain", in the usual way. The monomer is colored normally, while the other copies of the protein are normally gray. Changes made to the monomer are automatically reflected in the copies. The design goals for a oligomer are generally similar to those for a monomer. For example, the oligomer complex should be tightly packed, ideally with few voids between the monomer and the copies.