Performant drag & drop + FLIP animations were not trivial to implement (naive approaches like re-render fully on each mousemove fail spectacularly). I needed to

Performant drag & drop + FLIP animations were not trivial to implement (naive approaches like re-render fully on each mousemove fail spectacularly). I needed to see FPS on a couple different devices so I added the counter. Also, since I claim good rendering performance in the case study, I just kept it there as "proof" :)