There have been small flying insects flying around me, and I killed one after another. What happened?

Take you and me as an example. I work in front of the computer in my bedroom every day. A little black flying bug flies around me, killing one and then appearing a few minutes later. I can only see one at a time, one after another, and you have to die before the next one appears. I was drunk, so I named him Infinite Dead Worm.