An Air-defense (or air-raid) Drill

This afternoon, there was an air-defense drill from 2:00 to 2:30. But nobody ran out of the classroom and hid in the basement. It's not what I imagine. Ha. But it was funny, too. Because one man turned off the lights of my class, so all of us in the classroom only could see things clearly by the light from the computer's screen right in front of you. (But I think it's harm for eyes!! So, not again XD)