[nuccy]

The video is indeed very nice, it shows few things [1] not mentioned on the website:

- the chain is routed through the add-on device, so it should be longer than usual

- the pedals don't rotate when the chain and the wheel do, so there is a custom pedal hub with a ratchet mechanism

1. https://youtube.com/watch?v=SFsnS0Yb1Bs&t=83s