Is Hamlet sane throughout the play?

Hamlet, in my opinion is truly insane in parts of this play. At the first, I don’t think he was, but then having to deal with his father’s murder and having the weight of responsibility to kill his uncle, had a big affect on him and his sanity. I think anyone would go a little crazy under those circumstances, so I understand why he would go insane. I think if Hamlet was just pretending to be crazy he would have been normal at times too, but Hamlet never seemed to come out of it and he was insane all the time.