Twitch Icons
Twitch uses a custom version of Roobert called Roobert TW for display text as well as Inter for body text. When I first joined the company these 2 fonts were being introduced as a brand refresh that was internally called UV or Ultraviolet. My first task was to design a new set of icons to pair with these fonts, and I continued drawing those icons for all 4 years I was there. There are a bit over 300 total.
General Icon Rules
I developed a set of rules to keep icons consistent. Drawing icons is really fun, and I love that it let me interact directly with people on all different feature teams at Twitch.
20x20 for Web, 24x24 for Mobile. This was going to be consolidated into a single 24x24 icon set in a coming update.
2px stroke for all lines
2px gap between strokes
Try to avoid fills, when not attempting to communicate an active state on the icon.
Use 45 degree angles where the shapes allow
2px inner radius on corners
There are some exceptions to these rules on a case by case basis.