I see, thanks, I imagined (wrongly) that if your Wi-Fi router was down (besides Internet connection), even for a simpler issue, let's say a failed power supply, you were stuck with lights either on or off until you fixed it.

Besides my (personal) skepticism about anything IoT, I feared that in such a setup having a working Wi-Fi was "essential", if there is a failsafe of some kind (like direct bluetooth) it is less bad than I imagined.