Believability and convenience
There's an important balance to find between believability and convenience; it's easy to sacrifice one for the other. Believability is about creating a world that makes sense; one that's consistent with your theme, story, technology, characters, and more. In sci-fi, for example, the player may expect to find starships, aliens, and laser guns, but not elves, dragons, and undead mages. These elements simply don't belong. Convenience, on the other hand, is about the creative liberties we, as designers, take with the boundaries of reality to make things easier, more fun, or more accessible to the gamer. For example, traveling between villages in an RPG may take only minutes in real time, but represent weeks in game time. We don't make the player wait for weeks; we typically accelerate time for their convenience. When designing levels, we must find a middle point between these two extremes. Sometimes, we'll move closer to one direction than another, depending on the game. For Dead Keys, we'll take a convenience preference to facilitate the pick-up-and-play arcade feel. This will be reflected by a linear-level design allowing only one real route, by the staggered placement of enemies and a fixed-path camera. We'll include some props and objects to express a story now and then, but ultimately the experience needs to be smooth, progressive, and clearly action-focused. This damages the believability and narrative, but that's okay! We simply need to recognize that and focus on what's most important for our design and what our aim is--a fast-paced fun experience.