Drill 24: Invalid input — Classes, records and object design

public record Course(string Slug, string Title, int Lessons);

public class Progress
{
    public int Completed { get; private set; }

    public void MarkComplete(int total)
    {
        Completed = Math.Min(total, Completed + 1);
    }
}

var html = new Course("html", "HTML Foundations", 8);
var next = html with { Lessons = 9 };