Michael Shannon truely excels here when he exhibits his flawless adaptation to the character. He potrays himself to be more stronger when he emotionally and psychologically shifts characters back and forth from being sane to being mentally unstable.
On the whole the movie has a smooth and steady screenplay where the writer has taken thorough care in not rushing or increasing the pace of the film and that is the reason for the movie's impact on us.
I really appreciate the way the director has shown a sudden storm conjuring up at mid day and that's truely the time when one would least expect a storm. And, I think it really connects to the instability in Michael Shannon's mind as painted by the director.
Michael Shannon's daughter , ie; Hannah's inability to hear is also a direct connect to the film. It's seen in the film that Michael Shanon says that that the nightmares he encounters are not just dreams but they are REAL FEELINGS. And that's were Hannah's character in an add on. Although staying mute throughout the film she is a witness in many scenes when Michael Shannon hallucinates (feels).