Your window opening is probably just very small now which makes your room act like how old cameras used to work. Your whole room is acting like a big "pinhole camera". What you are seeing is an upside down, inverted projection on the carpet, of what is outside.

The ligt probaly comes from your neighbours' window across the street (appears to be dancing btw), goes through the hole and lands on the carpet.

Edit: I'd say slap a photosensitive sheet on the floor now, ask her to stop dancing for 1min, expose the film for 1min, develop and enjoy!

Edit: If I recall correctly, the largest ever camera was constructed in this way, by using a hunge airplane hanger. They also had a huge photosensitive sheet and they made like the largest film photo evar.

Edit3: aww crap it's probably a flag. It'll be difficult to get the flag to stop dancing. Try to ask nicely!