Man in Gap is not about a guy trying to find his way around a Gap store; the gap is quite literal here, as you can see in the screenshot.
Basically, each level is composed of a ceiling and a floor, which snap together quite suddenly. As can be expected, when that happens and you're caught in-between, you're squished to a very thin line of pixels. Not so good.
What makes it even worse is that the ceiling and the floor mostly interlock: They're like two pieces in a zipper, and where the ceiling has a "peak" the floor usually has a "valley" that meshes with it. You can see what I mean if you look at the jagged line in the screenshot - that's the contour of the floor and ceiling.
Lucky for you, there are one or two places in each level where the ceiling doesn't quite meet the floor. Your job is to quickly find those places (with your eyes only) and get to them before the level snaps shut. It takes about two-three seconds every time, so it's very fast. And every level has a different terrain, so you never get used to it.
Zero plot, minimal controls, and tons of fun. Really addictive, at least for me. I love the soundtrack, too - it's a nice guitar track with some hardcore distortion.