ruby_1
  1. general
  2. keywords
  3. math
  4. unit tests
  5. subroutings
  6. classes
  7. self
  8. super
  9. terminal
  10. strings
  11. arrays
  12. symbols
  13. hashes

    ruby_2
  1. regexp
  2. flow control
  3. exceptions
  4. iterators
  5. yield
  6. inheritance
  7. modules
  8. web-server