Principle 7: Overlay

Creates narrative and object spatial relationship in visual flatland when layered objects are location dependent. Overlay supports usability by allowing users to utilize flatland ordering properties to overcome a lack of non-spatial hierarchies. To land the plane a bit, Overlay allows designers to use motion to communicate location dependent objects that exist behind or in front of others in non 3D space. Credit: Bady, Javi Pérez In the example on the left, the foreground object slides to the right to reveal the location of additional background objects. In the example on the right, the entire scene slides down to reveal additional content and options (while using the Offset & Delay Principle to communicate the individuality of the photo objects). To a certain degree, as designers, the idea of 'layers' is so obvious as to be self-evident. We design with layers and the concept of layers are deeply internalized. However, we must be careful to distinguish between the process of 'making' verses 'using.' As designers who are continually engaged in the process of 'making,' we are intimately familiar with all of the pieces of the object (including the hidden pieces) we are designing. As a user, however, those non visible pieces are by definition and practice, hidden both visually and cognitively. The Overlay Principle allows designers to communicate relationship between 'z-axis' positioned layers and in so doing, promote spatial orientation to their users.