We have a solid AI with different levels of difficulty for exciting solo matches but most of all, we have a huge campaign. (blog.us.playstation.com)
Another (lesser) approach might be to negotiate different rate schedules for different levels of difficulty for the matter as a whole. (lawdepartmentmanagement.typepad.com)
To differentiate in response to student readiness, a teacher constructs tasks or provides learning choices at different levels of difficulty. (ascd.org)