How did Expressionist theatre sets reflect a character’s mental state?

In Expressionist theatre, sets were designed to function as a dramatic force rather than a realistic environment, reflecting the protagonist's internal state through abstraction and distortion.1

To externalize a character's psyche, designers employed several techniques:

• Distortion: Walls might be constructed at sharp, unnatural angles to create a sense of being crushed or threatened, mirroring the protagonist's anxiety or entrapment.1
• Symbolic Imagery: Elements of the set were often transformed into symbolic representations of the character's fears or obsessions. For example, trees might take the shape of skeletons to signify death, while windows could be lit to resemble eyes, suggesting a feeling of being spied upon.1
• Subjective Space: Settings were often highly subjective, existing to express the ideological position of the director or the mental state of the protagonist.1
• Juxtaposition: Incongruous elements were placed together to create visual tension, effectively communicating the fragmented or intense nature of the character's experience.1

By abandoning the simulation of reality, the Expressionist stage became a platform where the physical environment served as a tangible reflection of the character's inner consciousness.1