Realised that this is what I've got in the bedroom, in 'really obvious shit...' news
(I've moved in to parent's flat, and there are lots of things with no information or instructions and with which parent is unable to help.)
There are two ceiling lights, each with a central main light, surrounded by a border of low light that cycles through various colours. One press of the wall switch during the day activates one of the main lights, and three presses turns that off and the border on. At night, it seems to be the other way round. This was all very confusing when I discovered it.
Then, last night, one press of the wall swtich turned on both main lights, the second of which I had assumed over the last few months not to be working. Two main lights was like the glare of a thousand suns, but after about a dozen presses, I got it back to one light with only the border on, which is what I'd been going for. I did find a remote control the other day, that looks like it must be for some smart lighting system, presumaby this one. I did press several buttons to see if anything would happen, but it didn't at the time. However, I'm guessing that something I pressed activated the second light. Possibly. The remote doesn't have anything useful like a brand name on it, so I don't know what to search for.
Anyway. I've changed my vote to be like dessiato