struct Part1 {
    points: u32
}

impl Part1 {
    fn new() -> Part1 {
        Part1 { points: 30 }
    }

    fn points<'a>(&'a mut self, points: u32) -> &'a mut Self {
        self.points = points;
        self
    }

    fn run(&self)  {
        println!("{:?}", self.points);
    }
}

fn main() {
    let mut p = Part1::new().points(11);
    p.run();

    p.points(5);
    p.run();
}