Oh man, the original sketch to this is old, I think like 2015 old. It was my first drawing of a robot, ever. Once I finally got around to playing with ClipStudio I also started toying with brush packs. I think the random 'tubes' and 'wires' pack I downloaded did a pretty great job with the background, this is one of the few pieces where premade brushes worked out for me. I feel like most of the time, while the premade brushes are really cool and look great, if they don't match your artstyle or whatever you're going for they can really stick out and make the rest of the piece look quite bad. Guess I got lucky with this one.