Aesthetic integrity doesn’t measure the beauty of an app’s artwork or characterize its style; rather, it represents how well an app’s appearance and behavior integrates with its function to send a coherent message.
Consistency lets people transfer their knowledge and skills from one part of an app’s UI to another and from one app to another app. A consistent app isn’t a slavish copy of other apps and it isn’t stylistically stagnant; rather, it pays attention to the standards and paradigms people are comfortable with and it provides an internally consistent experience.
When people directly manipulate onscreen objects instead of using separate controls to manipulate them, they’re more engaged with their task and it’s easier for them to understand the results of their actions.
Feedback acknowledges people’s actions, shows them the results, and updates them on the progress of their task.
When virtual objects and actions in an app are metaphors for familiar experiences—whether these experiences are rooted in the real world or the digital world—users quickly grasp how to use the app.
It’s best when an app uses a metaphor to suggest a usage or experience without letting the metaphor enforce the limitations of the object or action on which it’s based.
People—not apps—should initiate and control actions. An app can suggest a course of action or warn about dangerous consequences, but it’s usually a mistake for the app to take decision-making away from the user. The best apps find the correct balance between giving people the capabilities they need while helping them avoid unwanted outcomes.