WTF are these tiny flies?

[CrimsonElevenDelightPetrichor]

There are thousands of them crawling on the kitchen floor near the patio doors. Nowhere else in the house that I've seen so far.
Just appeared in the last few hours while I was out.

They must have hatched… although flies are usually maggots 1st.

We get like flies like that when our bananas have gone off

Bloody hell that's an invasion! Do you have any rotting food you don't know about or a dead mouse lurking somewhere?

Is there decking the other side of the patio doors? Could something have died under there?

Could they be flying ants that have come out of their nest?

Fruit flies? But they usually fly, albeit very slowly, they’re quite ‘bumbling’ for want of a better word. Any rotten fruit, anything steeping in water for too long or a new plant? It’s quite a lot to have appeared in one go! Those three and a new item of shopping that’s a plant or fruit would be what I was investigating.

Sorry photo is a bit blurry. Definitely flies not ants.
Patio outside, no decking.
No rotten fruit, no mouse carcass in the vicinity. I do have a cat, who I blame for most unexplained things, but I can't see how this is her fault.
They look more like fungus gnats than fruitflies, but they aren't particularly near any plants.
I've sprayed them with flash bleach spray, which appears to have killed them but I really want to know where they're coming from.

I did buy a new plant but it's nowhere near the patio doors.
It's all a bit 🤮

They’ve gone to the patio doors because they’re attracted to the light - I suspect new plant is the culprit.

There are no flies near the new plant - it is in a different room. No flies near the window in that room.
Still 🤮

I need to know where these are coming from! I’m so invested now!

Me too ☹️

UPDATE!
They're coming from under the fridge. It's a big fridge-freezer so I can't tip it up on my own to investigate further, but someone can help me in the week. In the meantime I'll just squirt bleach spray around/under it.
I'm fairly horrified about what I'm going to find underneath it. Revising my opinion that this isn't the cat's fault. 🙀

Hey I have had these for a few days I was bleach spraying them and they would return.

I went and bought Raid for ants and cockroaches and sprayed everywhere then shut the door.

This morning there is nothing.

I guess something has got stuck and died under there, maybe a mouse? Or it could be a spill, but unless you have an idea what could have been spilled under the fridge from behind/the sides? What could that be? (In our kitchen you could have a spill from the side because there's a counter next to it where people make drinks).

I've moved it out and cleaned around/behind it, but I need to look at the underside. 🤮

Well that's a problem then. I can't use Raid because of the fishtank in the room.
Hopefully I'll be able to find the root cause in the week.