Point Blank question

In this book, I think that one of the flat characters is James Sprintz, and one of the round characters is Alex Rider. I think James is a flat character because he only really has one trait, being a trouble-maker. Also, the definition of a flat character is like a two-dimensional character meaning a character with only one trait. "Honestly, the only thing he was good at was making trouble"(92). In the mean while, Alex is a round character because he has many traits like brave, strong, and fearless, and the definition of a round character is a character who has many traits or like a three-dimensional character. "'Come on, he is strong, and brave, we need him!'"(47). This is why James Sprintz is a flat character and why Alex Rider is a round character.