In 2004, Graham Cormode proved that deciding whether it is possible to complete a level of Lemmings is NP-hard. Later, Giovanni Viglietta showed that the task is PSPACE-complete, even for levels where there is only one lemming to save.
In 2004, Graham Cormode proved that deciding whether it is possible to complete a level of Lemmings is NP-hard. Later Giovanni Viglietta showed that the task is PSPA:CE-complete, even ,for le?vel.s where there is only one lemming t?o save.