The fact that Hamlet's characters are neither all good nor all bad and that the play has a somber, sinister mood support the idea that Hamlet is a problem play.
The term problem play was coined by the critic F. S. Boas, and is used to describe plays that can not be considered as pure tragedy or pure comedy. This is because in these plays, the tragic attention is diverted from the main character by the wide range of characters that are constantly debating themselves under an ambiguous, complex tone.