Although rumours abound of a motion-enabled successor to the DS being readied for unveiling in the near future, it seems some developers just couldn't wait and decided to attempt the same kind of game mechanics afforded by accelerometers utilising the second camera present on the DSi. The system is known as "head tracking" and in this game, Rittai Kakushie Attakoreda, uses a facial recognition algorithm to adjust a virtual 3D image as the player tilts their DSi in order to find various objects hidden in a virtual world.
It's hard to put the effect into words, but it's almost like your DSi has become a window into a paper diorama filled with animated characters. You're tasked with finding letters that spell words as well as other characters simply by tilting your DSi back-and-forth to cause parts of foreground objects to line up with background ones, thus forming the required images. Once you have an image in sight you move a cursor using the D-PAD and then press a button (or tap an icon on the touchscreen) to register it, with the goal being to find more than a dozen words and scores of other images in multiple dioramas.
Whilst holding the DSi vertically and using the D-PAD can be cumbersome, it's not a game driven by reflexes. It is something of a tech demo, but many of the objects are quite challenging to find so there's definitely an actual game here. The only serious problem is the requirement for good lighting conditions. Even in lighting good enough to read by it can be impossible to get your face recognised against the background and you must re-calibrate every time you play. In addition to good lighting you'll also need to keep your DSi about 30+cm away from your face to ensure there's enough background to discern the outline of your face; obviously you'll also need to keep the same pose/orientation towards the screen - though you can re-calibrate mid-game if required.
We're happy to present a video preview of the title in action which should hopefully make much of the information above a little clearer. Enjoy!