Science Fair

Just found out today that I have to make a project for the science fair. I have absolutely no idea what the topic should be. I was thinking something that's not too hard and not extremely easy. At the moment I'm thinking of making my project on optical illusions or mold. I'm probably going to choose optical illusions over mold but I'm not sure how to make it. I asked a few of my friends on a few possible topics. Most of them didn't have any ideas. One of them told me about the optical illusions idea. I probably owe her something now or I can just help her with math. Luckily next class my science teacher will probably give us a few topics that people can use. For now all I can do is think of a good topic and find out how to make the project.