17.11 THE TETRIS TEST The ideal experience is uninterrupted calmness and serenity with mild chal- lenge to keep the engagement level high. Challenge: What are the intended challenges of the game? What types of chal- lenge is the game about? This will keep clear the distinction between usabil- ity issues and game design issues. Is the game about quickly and decisively taking very specific tactical actions, like Bungie's Myth, or is about manag- ing your own attention--figuring out what's important amidst a roiling sea of ever-changing unit movement and building upgrading as in Rise of Nations? Or maybe there should be no time pressure at all, as in Civilization 4, and each tiny decision should be deliberate and intended to further a greater over-arch- ing strategic goal. Whatever the real challenge is, try to make sure it's clarified such that there is no ambiguity between usability and game design issues. 17.11 The Tetris Test For the sake of brevity, I'm going to fill this out using Tetris, a simple game that most people have played at least once. See the end of the chapter for a blank version of this prep sheet or go to www.steveswink.com/usability/ for downloadable versions.