The film hits you in the face hard at the beginning, as Bullocks character, we find out later is the last woman is standing - the survivor of a mysterious force sweeping the planet.
Her interaction with the two small children seems inappropriate, but does convey the urgency of the situation and it grabs your attention.
That continues through the film.
A mysterious force, sending people into a unexplained misery explained later in the film which has something to do with an effect on the victims eyes, which seems to be their worst fear. To the sane it’s their worst fear, to the mad it’s their most beautiful vision, an interesting contrast.
As the film progressed, I felt empathy for the small children - especially the girl as she seemed to cop the brunt of Bullock's fury, and harshness. There are scenes towards the end of the film where she clearly feels favouritism towards her child, but remembers the promise to her now deceased colleague who wanted a promise to protect her child if anything happened to her, which Bullock seemed to reluctantly give.
Bullock’s character seems to resist the idea of parenthood throughout the film, but resolution does seem to come when she pleads with the mysterious force to not take her children, as if she is imposing her will over the force and taking responsibility for them - because at the prospect of losing them, she just cannot have it.
This is when Bullocks character steps into her parenthood, a mother’s instinct to protect her children like the mysterious force, Bullocks character imposes her will over the mystery, and guarantees the children's safety.
This film has an underlying narrative of what it means to be a mother/parent, countering the mysterious force with an equally mysterious force that is of a mothers/parents protective instinct.
The overwhelming sense I got from this film is just sadness and the reaction that people have to such sadness, maybe a reaction to their own loss of youth, people go mad - they either go into survival mode, or give hope to others by protecting and nurturing.
Bird box is an ode to the terror and rewards that come with parenthood.