The things of everyday design

In 1988, Don Norman published The Design of Everyday Things, he coined the concept of “affordances” The concept is a relationship between the properties of an object and the capabilities of the agent that determine just how the object could possibly be used. A handle on a door is an affordance: it indicates that the door should be pulled. A good affordance takes advantage of some natural interaction between a thing and its user. If something has visual feedback mechanisms, those mechanisms should be at eye level.