/ic/ - Artwork/Critique

how do you into clean as fuck line art like this? or i guess just any theories on line art in general that you know; I can't seem to grasp it at all. specifically i'm interested in the extremely subtle variation of line weight in images like this. looking at it it deceptively looks like all the same line weight at first but if you focus on any particular part you can tell it's slightly varied to imply depth. but I'm sure the artist didn't just add some random bumps and indiscriminate scribbles here and there just for the sake of avoiding flatness; it looks very deliberate and controlled and I can't figure out the underlying concept, whatever it may be, no matter how long i stare at it.

the only "theory" about line art I've ever read is that closer forms are outlined more thickly, but of course it's not as simple as that.