Four of a colour in a row or column clears. Beads falling into the gap can clear again — that is a chain.
Pairs of coloured beads fall. Link four of one colour in a row or column and they vanish; whatever was above drops into the gap, and if that lands four in a row it clears too. The longer the chain, the sharper the score rises.
Questions
Do I need an account?
No. Opening the page is the whole setup.
Where does the score go?
Into this browser on this device. Nothing is sent to a server, so it does not follow you to another device.
Does it work on a phone?
Yes. The pad and drop button below the board are sized to be pressed with a thumb.
Does it work offline?
Yes. Once the page has loaded, it plays through with the network off.
What if I stop halfway?
The board and score are kept, and reopening the page resumes from there.
Is there sound?
It starts off. The button below the board turns it on, and that choice is remembered.