## 1 Introduction  
_You've trailed the killer through fields, across rivers and under bridges, from downtown to the edge of town, his taunting voice echoing in your head the entire way...and now, finally, he's made a mistake. It's a minor one, as mistakes go, but you've been able to follow an errant word, spoken in jest, to new evidence deep in the university's library. And now you have him. \"It's only a matter of time,\" you think to yourself as you rush out the front doors of the library and toward your car, \"soon I'll track him down and then he'll have to tell me what really happened to my son\". There's no escape for the monster this time. Reaching the parking lot, you drop heavily into the seat of your car, the exhaustion of hours of non-stop, hurried walking spreading through your legs at the sudden reprieve. You turn the key in the ignition, flip on the headlights, and roll out of the lot, pointing the car in the direction indicated by the killer's final message...and your stomach grows. Exasperated, you realize that you forgot to stop at the grocery after getting off work again. There's no food in the house, and you know that you really should try to cook something healthy tonight. You've been eating too much fast food lately and you don't want it to become a habit. With a heavy sigh, you fold up the killer's last taunting note and shut down your GPS unit. You'll have to pick up the chase when the weekend rolls around..._  
What we've just described is a hypothetical player's experience of our hybrid-reality game (HRG) _University of Death_. Mobile gaming researcher [PERSON] defines HRGs as games that \"employ mobile technologies and GPS devices as tools for transforming physical spaces into interactive game boards\" [1], and _University of Death_ (_UoD_) achieves this transformation by mapping a number of GPS-powered _ludic_ challenges onto the geography of the actual city of Pullman, Washington. From a _ludic_ perspective, _UoD_ is half scavenger hunt and half puzzle game: players travel across the city, following clues and GPS coordinates to a series of story-caches [2]. In addition to providing them with the next location in the sequence, each successive story-cache presents players with another piece of a larger murder-mystery puzzle that they must eventually solve in order to complete the story and \"win\". In this sense, _UoD_ is certainly a game; however, it is also an experiment in storytelling. In creating _UoD_, we wanted to do more than just make a \"game board\" out of the city of Pullman: we also wanted to use the medium of hybrid-reality gaming to explore the unique opportunities that the mobile internet affords storytellers. While this essay is not focused on _University of Death,_ it does build upon our experiences creating that HRG in order to interrogate the larger theoretical issues inherent in storytelling through mobile gaming. Ultimately, we argue that the mobile internet expands the immersive potential of in-game storytelling in new directions by enabling the creation of games powered by portable, location-aware interfaces. We believe that the mobile gaming format [3] has thus become the latest iteration in a decades-long evolution of digital games of various platforms that seek to empower the player not just as an avatar in a gameworld but also as a co-author of that gameworld, alongside the gamemaker(s). Like video games before them, then, mobile games eschew storytelling _via_ traditional linear narrative structures in favor of a nonlinear, cooperative storytelling process. Unlike video games, though, mobile games are uniquely able to extend this cooperative storytelling process into the physical world through the use of location-aware interfaces, enabling the achievement of a new level of player immersion. In mobile games like _UoD_, players are encouraged to implicate places in the physical world as part of their gameworld, while also overlaying elements of the gameworld onto the physical world.