Brain Snacks: Tasty Tidbits of Knowledge
Even though Marie Lu wrote Legend as an adult, she's apparently had the idea for the character Day floating around in her head since she was fifteen—coincidentally the same age Day is when the story opens up.
(Source)
Even though Marie Lu is writing full-time now, she used to be pretty immersed in the gaming world. Before writing Legend, Lu worked at a company making Facebook games. (Source)
Since Legend is the first book of a trilogy, it makes sense to wonder what the next books will bring. Lu gives us a hint by saying that the last book, Champion, was the only one that made her cry while she was writing it. Uh-oh. (Source)