Which design principle uses visual barriers to keep designs organized?

The correct answer, which highlights the use of visual barriers to maintain organization in designs, is containment. Containment refers to the strategic placement of elements within defined boundaries, such as boxes, lines, or other visual cues, to create a sense of structure and clarity. This approach allows designers to effectively separate different sections of content or functionalities, ensuring that users can easily understand and navigate the design without feeling overwhelmed by visual clutter.

By using containment, designers can guide the user's eye and help them focus on specific areas of a layout, thus enhancing usability and comprehension. Additionally, containment aids in establishing a logical flow within the design, reinforcing the relationships between different components. This method is integral in producing aesthetically pleasing and functional interfaces.

Hierarchy, while it also plays a critical role in organizing elements, focuses primarily on establishing an order based on importance or sequence rather than physically separating them with barriers. Emphasis refers to drawing attention to particular aspects of the design, and unity is about the overall coherence and consistency of the design elements. While all these principles contribute to effective design, containment specifically addresses the aspect of visual barriers that helps in maintaining order.