This reminded me of something I did almost two decades ago now that I feel really improved my ability to program in Ruby at the time. I spent months reading through ActiveSupport and Rails source code and re-implemented whole subsystems on my own to just understand how they worked. I had a blast and learned a ton along the way not just about ruby but about software engineering and being able to process and understand "large projects". At the time, I also remember really enjoying Jim Weirich's talks and his good-natured personality inspired me to dig into rake and rubygems as well.