gistfile1.rb

index.rb

require 'sinatra'
require './lib/game'
require './lib/problem_set'

get '/' do
  @game = Game.new
  @problem = ProblemSet.random
  erb :index
end

post '/answer' do
  "Hello World '#{params[:answer]}'"
end

index.erb

Problem Set</br>
<%= @problem %>
<form action="/answer" method="post">
  <input type="text" name="answer">
  <input type="submit">
</form>