How Do You Decide on What Project to Work On?

How do you decide on what project to work on? That was a question we asked. I think deep down, I like to see an equation that I can solve. And if I like the look of it, I will often just go for it. It doesn't necessarily mean that I'm going to try and solve how the universe is behaving at the moment. I just love solving equations. So I think the beauty of the maths often grabs me. The strings could be telling us something about the distribution of large-scale structure. Yet there was so little known about their dynamics.