A crude measure of the simplicity of an engineering tool is the length of the manual required to give a full and complete account of how to use it and avoid misusing it.
“A record player, a kitchen appliance, a slide projector or a shaver with disorderly, chaotic, confusing or overloaded design cannot fulfil its functions. The harmony of a design too, its aesthetic quality, also has a functional purpose—it facilitates a positive emotional relationship between a device and its user.”