anttis_flipper.rb

require 'rack/request'
require 'rack/response'

module Anttis
  class Flipper
    def initialize(app)
      @app = app
    end

    def call(env)
      status, headers, body = @app.call(env)

      body.extend Enumerable
      body_string = body.inject { |a, b| a + b }

      req = Rack::Request.new(env)
      res = Rack::Response.new      

      res.write(flip_pres_lines(body_string, req.GET["flip"]))
      res.write "<p><a href='?flip=#{flip_flip(req.GET["flip"])}'>flip!</a></p>"
      res.finish
    end

    private

    def flip_pres_lines(string, flip)
      if flip == "left"
        string.gsub(/<pre>(.*)<\/pre>/m) { "<pre>#{flip_lines($1)}</pre>" }
      else
        string
      end
    end

    def flip_lines(string)
      string.split("\n").map { |line| line.ljust(42).reverse }.join("\n")
    end

    def flip_flip(string)
      if string == "left"
        "right"
      else
        "left"
      end
    end
  end
end

anttis_lobster.rb

require 'zlib'
require 'rack/request'
require 'rack/response'

module Anttis
  class Lobster
    LobsterString = Zlib::Inflate.inflate("eJx9kEEOwyAMBO99xd7MAcytUhPlJyj2
    P6jy9i4k9EQyGAnBarEXeCBqSkntNXsi/ZCvC48zGQoZKikGrFMZvgS5ZHd+aGWVuWwhVF0
    t1drVmiR42HcWNz5w3QanT+2gIvTVCiE1lm1Y0eU4JGmIIbaKwextKn8rvW+p5PIwFl8ZWJ
    I8jyiTlhTcYXkekJAzTyYN6E08A+dk8voBkAVTJQ==".delete("\n ").unpack("m*")[0])

    def call(env)
      res = Rack::Response.new
      res.write "<title>Lobstericious!</title>"
      res.write "<pre>"
      res.write LobsterString
      res.write "</pre>"
      res.finish
    end
  end
end

lobster.ru

# To run this:
# rackup -p 80 lobster.ru

require 'anttis_flipper'
require 'anttis_lobster'

use Anttis::Flipper
run Anttis::Lobster.new