I can’t give specifics since I haven’t really touched board rendering, but I think these are the files you would want to look at:
- goban/src/GobanCanvas.ts at main · online-go/goban · GitHub
- goban/src/GobanSVG.ts at main · online-go/goban · GitHub
- this is a new, experimental board that may replace the old one (New experimental SVG based goban renderer)