If you really want to expand your horizons try to write an operating system. It does not have to be from the metal up or involve kernel authoring. It can be as

If you really want to expand your horizons try to write an operating system. It does not have to be from the metal up or involve kernel authoring. It can be as an application in your current OS, or even something that works in a web browser. Writing a new OS will force you to consider security handling, transmission limitations, performance, original usability problems, organization that scales in multiple directions, and so on.