modified:   chapter_01/1_stroke_and_fill.rb
	modified:   chapter_01/2_nofill.rb
	modified:   chapter_01/4_alpha_transparency.rb
	modified:   chapter_01/5_zoog.rb
	modified:   chapter_01/Rakefile
	modified:   chapter_02/1_zoog_again.rb
	modified:   chapter_03/Rakefile
	modified:   chapter_04/1_variable_declaration.rb
	modified:   chapter_04/3_varying_variables.rb
	modified:   chapter_04/4_many_variables.rb
	modified:   chapter_04/5_using_system_variables.rb
	modified:   chapter_04/Rakefile
	modified:   chapter_13/06_oscillation.rb
	modified:   chapter_15/06_pixels_2d.rb
	modified:   chapter_18/02_graphing_comma_separated_numbers_from_a_text_file.rb