In Tennessee Williams' play A Streetcar Named Desire, stage directions play a critical role in informing the audience about characters' emotional states and intentions. Consider the following excerpt from the play’s stage directions:
"As BLANCHE struggles to remember, her body language shows tension and vulnerability, contrasting sharply with STANLEY’s robust posture, which asserts dominance. The dim lighting casts shadows that envelop BLANCHE, isolating her even further."
Based on this description, how does Williams utilize stage directions to develop the theme of power dynamics between the characters?