string-reversed.rb

def reverse(string)
  # gets (input from STDIN) isn't necessary cause you get string argument in this method
  # input = gets.strip

  # You should split your string by empty string to get an array of it's chars
  string_array = string.split('')

  # Class name should be started from a capital letter
  new_word = Array.new

  # You get only last letter here, but it's probably should be in loop
  # last_letter = string_array.pop
  #
  # if string_array.length > 0
  #   new_word.push(last_letter)
  # else return new_word.join
  # end

  while letter = string_array.pop
    new_word.push(letter)
  end

  # In Ruby you can ommit return keyword if you just want to return the last value
  new_word.join
end

p reverse("Look at me, I am reversed!") # => "!desrever ma I ,em ta kooL"