system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:Why can't flies get out of open windows as soon as you open them?
gpt
Imagine being in a very large room, and you can only see a small part of the room at any time. Someone makes a small opening (door, window) in one part of the room.

You can't leave immediately since you don't know it's open until you explore it.

On top of that, flies are very bad at figuring out transparent obstacles. A window might look open, but is actually closed.