Keep the user engaged Engagement is as important as ease of use. Engaging features can hinder usability: Randomness Not omnipotent Effects proportional to action Action entails risk The game metaphor and interface lend PSDoom a compelling narative that makes it engaging. For a task that requires the user's attention to monitor a system, engagement is as important as ease of use. Features that make an application engaging can actually hinder usability (read bullets).