I move through the interstitial layers, I smoke in the basement, I write in the margins, and grow in the cracks

I'm lost and I'm looking, all around the edges, and I'll never find more than a crumb because it's designed that way

They say I've lost thirty-percent of my mind, but not the main part

I'm only seen when there aren't many people around, I'm only heard by accident

I don't speak, unless someone speaks to me, but who would want to?