You play as Kirra, a thief for hire who has been tasked with retrieving an ancient mirror from some similarly ancient ruins. When she finds the mirror, it does what all ancient mirrors do: it breaks. And in doing so, the mirror shatters her reality as well. She now has to reassemble the mirror if there is any hope of restoring her world, and she does this by traveling through both her world and the mirror world, reflected in the DSi's bottom screen.
Reflection a bit like Mirror's Edge meets ... well, a mirror. Kirra can run, jump, slide, and wall jump with a truncated set of Faith's parkour moves; however, the twist is the inclusion of the second screen, and you'll run into completely different obstacles on both. Barriers, pits full of spikes, sheer drops, and more.
You'll have to figure out how to get Kirra past the obstacles on both screens, because what happens on one screen will be reflected on the other. For example, if you jump to a platform on one screen, your Mirror-Kirra may be standing (safely) on thin air. However, if you slide under an obstacle on one screen, and Mirror-Kirra falls off the map, you die. Both versions of Mirra have to survive for you to continue.
In some levels you'll encounter a dark, shadowy version of Kirra who is de-synced in time from her other self. If you jump on one screen, it might take Shadow-Kirra a second or two to jump. As you'd expect, these levels are much harder, and you'll have to find creative ways to continue on.
Konami estimates that it will take roughly three hours to complete Reflection's main quest, and longer if you're trying to track down all of the journal pages (detailing the mystery of the mirror and how it was created) and explore all of the areas. You can also unlock Expert Levels and a Time Attack mode to extend the experience.
The innovative gameplay really defines this game, but the short completion time and the low production values detract from the overall experience. But if you're looking for an unique DSiWare title that, notably, started as a student project at USC, you owe it to yourself to check out Reflection.