The document discusses key principles of design including balance, rhythm, scale and proportion, emphasis, and harmony. It defines different types of balance, rhythm, and harmony. For balance, it describes symmetrical and asymmetrical balance. For rhythm, it outlines rhythm by repetition, gradation, radiation, opposition, and transition. It also discusses scale and proportion in relation to object and room size. Emphasis and harmony are achieved through various design elements and arrangements. Unity and variety are both important for an harmonious design.