- Didn't realise that nil.to_i = 0 https://stackoverflow.com/questions/11029256/difference-between-nil-blank-and-empty - Interesting that .count and .size doesn't just count number of elements in array. If I did (1..5).count or .size # => 5 If I did .length, it would have an error. .count { | i | not i.to_s.include? '5' } can be used as a block. - .reject It's cool that reject blocks can be used in this manner: 1) .reject { |e| e.to_s.include?('5') } 2) .reject { |n| n.to_s =~ /5/ } Both achieve the same thing. - Ruby formatting. This is very new to me. ("%-5s" % "teg") => "teg " It's like saying the format is 5 characters in a sring. https://idiosyncratic-ruby.com/49-what-the-format.html - .ljust expands the string or if there is an integer, fills the strings to the number of characters. "hello".ljust(4) #=> "hello" "hello".ljust(20) #=>...