User Interface

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I don't have a formal education in user interface design, but I'm always amazed by bad design, despite that I think it is very simply to check if you have a good design.

Four Simple Considerations

It seems to me there there are only four things to consider:

Fitts's Law

Fitts's Law can very accurately predict the time to acquire a target. It is an extremely successful model in user interface design. It applies to all user interfaces, including computers and mouse pointers. Basically it says that it is easier to press a large button which is nearby.

If you don't know Fitts's Law, you should read this small quiz with its answers: A Quiz Designed to Give You Fitts.

Clarity of Arrangement

Consistency in the interface is slightly more important then accuracy. For example, use consistent names in menus, even if they are not always 100% correct.

Undo

Allow users to make mistakes. Provide an undo option. If a users makes a mistake and the program allows him to revert the mistake, it build confidence in the program. Adding an undo option will have a great effect on the perceived reliability then making it crash less.

Modelessness

Eliminate state! Make sure that a behaviour is consistent at all times. Allow users what they want to do at all times. Make this consistent. If a users wants to scroll down a page, make sure the scrollwheel sometimes has a different meaning because some element is selected.

Modelessness (as opposed to modal, or stateful, behaviour) is even more important in consumer electronics. Surely you experienced the frustration of change the (saylight saving) time on some gizmo with a digital clock. First press button A for 3 seconds to enter 'time edit mode', then change button 'B' to advance the time, or button 'C' to change from hours to minute editing mode. More (or less) buttons is not necessarily better. It is just that the fact that a buttons behaves differently according to some state. Eliminate this state!

Further Reading