Set the structure, press start, and put it on whatever screen the room can see. It counts down the level, announces the next blinds, and keeps going until somebody wins.
Nothing is stored and nothing is sent anywhere — once the page has loaded it will keep running with the wifi off.
The single biggest cause of argument in a home game is somebody not knowing the blinds went up. A clock on a screen ends that permanently, and it ends the job of whoever was previously keeping time in their head.
A level change in the middle of a hand is awkward — the hand finishes at the old blinds. A visible warning means the dealer can decide whether there is time for one more, which is the convention every card room uses.
Once this page has loaded, the clock is running in your browser and nothing else is needed. Close the wifi, close the laptop lid at your peril, but the network can go down and the tournament carries on.
Yes — press F11 in most browsers. The display scales to whatever screen it is on.
Changing any setting rebuilds the structure and resets to level one, so set it before you start.
Only to load. After that it runs locally and nothing is sent anywhere.