Chapter 4 - Case study: interface design #2
Description
Chapter link: https://github.com/learnbyexample/ThinkRubyBuild/blob/master/chapters_md/case_study_interface_design.md
Main issue: couldn't install turtle in Ruby and had issues like mentioned here peterc/trtl#5
Possible solution, use Exercise 3 (grid drawing) from Methods chapter as a base to teach concepts like Encapsulation, Generalization, Interface design etc