uninitialized constant error (Ruby Sinatra)

[donchev1]

Hey guys, I am quite new to programming and I can't call a certain method in file from a different file.
I am using Sinatra and I am trying to display some input to a browser. According to my practical sheets from uni this is supposed to display the number from source file to the browser. It works for the command line window but not when I am calling it from the layout.rb file. It is giving me uninitialized constant error. Please Help!

mainfile.rb

require "#{File.dirname(FILE)}/source"
require 'sinatra'
get '/' do
home :erb
end

source.rb

module OXO_Game
class Game
attr_reader :input, :output
attr_writer :input, :output
def initialize(input, output)
@input = input
@output = output
end
def student_id
@student_id = "51235134"
end
end
end

layout.rb

<% require "#{File.dirname(__FILE__)}/source" %>

                <% module OXO_Game %>

                <% @input = STDIN %>

            	<% @output = STDOUT %>

            	<% g = Game.new(@input, @output) %>

                    <% g.student_id %>

            	<% end %>

<%= yield %>