Then a flash of light occurred at what seemed to be the lower left of the screen;

随后，一道闪光出现在屏幕的左下方；

youdao

A flash mob is a group of people who come together suddenly in a public place, do something unusual for a short period of time, and then quickly break up.

快闪族，是指一群人突然在公共场所聚集，在短时间内做一些不寻常的事情，然后迅速散开。

youdao

Then all of a sudden, she saw a big flash.

突然她眼前出现了一道闪光。

youdao

Then, in a flash, it will all be over.

ECONOMIST: To the ends of the earth

Then he had a flash of genuine brilliance, scripted or otherwise, by pointing out that the Tory party was full of people who were "either in jail or had just come out of jail".

BBC: By Nick Assinder

And then, the visitor disappeared in a flash, just as if a TV screen had been turned off.

FORBES: An Internet Carol