Atum is a game in which you play as someone who's playing a 2D platformer. It is, however, by most standards not a particularly good platformer, as it requires that you be a habitual smoker to beat it. That's what makes Atum so neat, though: objects inside the main character's exceedingly white (and literary) apartment influence what unfolds on the screen within a screen. Need to get past a security camera? Just use your cigarette to create a smokescreen. Can't see in the dark? Hold your lighter frighteningly close to your very expensive-looking computer monitor. Etc. Etc. Etc. It's well worth a look, I think - in spite of some clunk in its trunk.
I suppose my main issue is that, while the "real"/virtual world interaction gimmick is striking, it ends up becoming tedious fairly quickly. Magnets and smoke, especially, are very finicky, and I found myself picking items up, putting them down, and picking them back up again far more often than I'd have liked. Sure, it's definitely a little thing, but it made me realize that turning my in-game abilities into "real" world objects almost hurt the experience more than it helped.
Moreover, most of the puzzles weren't particularly interesting - more teaching me the basic mechanics than actually leveraging them. But then, Atum's a relatively short game, so that's sort of unavoidable. I'd love to see this idea expanded outside its current, relatively confining box, though. Not literally, of course. Then it'd be a game in which you play as someone who's playing as someone who's playing a 2D platformer. And that's just enough meta-levels to make me start asking unsettling existential questions. In other words: too many.