Ratio·9 needs JavaScript, because the click is scheduled in the Web Audio graph in your browser. Here is what it does.
Set the click to 70 BPM. Play two bars of eighth-note triplets, three notes per beat, then two bars of sextuplets, six notes per beat, without touching the click. The pulse never moved and your picking hand just doubled its speed. That ratio, not the tempo dial, is what builds speed: you reach the fast motion immediately, against a beat that stays put, so any drift is audible against a reference that did not shift.
The method is written up in full in the field manual, which reads without JavaScript. Source code: github.com/frankbirzle/ratio9