Flattened depictions can be found in traditional black and white silhouettes, though white, any color, or a shade of gray might be used within the flat shapes. Form is only suggested by the outer boundaries of the flat shapes. Total flattening of objects often makes them into icons for the type of person, animal, object, etc. they are, de-emphasizing individuality.
The features of a face or the limbs of a body might each be rendered as a flat shape, but each is treated as a 2D surface, with no indication of 3D form. It is only the viewer's familiarity with a given subject that might lead to the interpretation of three-dimensional volume or space.
Flat shapes for each object might be used to emphasize the abstract composition of the scene being depicted. The flatness might imply shallowness. Or it could highlight the isolation of one character from another.
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