Which aspect of design does the principle of proportion focus on?

The principle of proportion focuses on the harmony between elements of different sizes. In design, proportion refers to the relationship in size and scale between different elements within a composition. It dictates how these elements relate to each other and to the whole design, which is key to creating balance and visual harmony. Proportional relationships help guide the viewer's eye and can establish a sense of order or chaos, depending on how they are applied. This harmony is crucial in ensuring that all elements work together cohesively rather than competing for attention or creating a visual imbalance.

The other aspects mentioned, such as color selection, simplicity of design elements, and typography, are important design principles, but they pertain to specific areas of design rather than the overall relationship between sizes and scales of different elements.