Rückblende (German for "Flashback") is, in essence, a Quicktime art film with mild interactive elements that qualify it, in some sense, as a graphic adventure. It's notable for its unusual look and the emotions it evokes: a sense of nostalgia and poignancy.
It appears that the creator, Nils Deneken, began by building a physical model of a house in the woods and its surroundings, then filming and photographing the model, imposing small hand-drawn animations atop the images at times. Most of the time, you're viewing a static photograph, with hand-drawn objects or control icons representing movement atop it; mousing over or clicking on one of the icons causes a brief movie to play. In some cases, this is a pan across the model to a new physical location; at others, a scene from the protagonist's childhood is played out. As in Czech animation (and there does seem to be a visual debt to that tradition), there is no dialog, though there is a musical score.
Technically very simple, but visually appealing, and quite an unusual way to go about building an interactive application.
It's not a game in the usual sense (though it is part of this year's IGF student showcase) -- there are no puzzles, nor any real goal -- but it is an interesting, somewhat meditative experience.