Simplify the following text for a Grade 15 native English-speaking person.
Original: Postmodernism in architecture is marked by the re-emergence of surface ornament , reference to surrounding buildings in urban architecture , historical reference in decorative forms , and non-orthogonal angles .
Simplified: Postmodern architecture returns to surface ornament , historical reference in decorative forms , and non-orthogonal angles ( less box-like shapes ) .