Once the application's functionality is defined, then the design must be considered. Interface design is an increasingly important element of successful software applications, especially with the advent of multimedia technology and the use of the computer as an information tool. But one of the hardest parts of designing a great application is the blend of functional and visual design. Screens must appear attractive to the user, yet the interface design must reinforce the functional design of the application. A well-designed application will hide powerful functionality behind a simple interface. Most computer users already understand the basic behaviors of Windows or the Mac OS, and a good application interface design will leverage the experience of the user to make the application easier to comprehend and use.