Tidy your room! 12 Things

How do you get a nine year old -Thing 2 to tidy her bedroom?
After many many different ways ranging from the very simple of requests to bribery I found a new method.
Yesterday, her room was once again ridiculously untidy. Trying to get her to tidy up as she went along obviously hadn't worked so I decided to make a game out of it.
First, I asked her to pick up all of the toys and junk that had accumulated on her bed so I could change it. Then I asked her to pick up 12 things off of the floor which should really be in the bin. She thought this was good fun. Once she had counted out 12 pieces of rubbish and put them in the waste basket, I then told her to pick up everything off of the floor that needed to be put away - at least 12 things. Next, I asked her to pick up 12 things off of the desk, which had also become a dumping ground. Another 12 things off of the bookcase which shouldn't be there. Now it is possible to see how pretty the room could look she has promised to finish off her desk and bookcase tomorrow.
Tomorrow is here and -I'm still waiting.