Nature flies

My home is being invaded by dozens of tiny black flies, about three mm long and thin.Can anyone tell me what I am facing here?

Edit: There's one crawling on my computer screen. At least I thout it was crawling on it. But it is crawling around INSIDE it. Even if it curls up and dies right now, I'll always have it in front of me.

Edit: This is my window from the outside, after I closed it. Most of the crawlies are caught in spiderwebs.


Also, the bug in my computer screen has died. Inside the visible area, of course.