success.rb

# Ruby 2.2.1

require 'httparty'

URL_PREFIX = 'http://www.wholelattelove.com'
@leaf_url = ''

def response(suffix)
  HTTParty.get(URL_PREFIX + suffix)
end

def branch(node, direction)
  puts "Checking #{node}..."
  @leaf_url = URL_PREFIX + "#{node[direction]}"
  branch = response("#{node[direction]}")
  fetch_node(branch) unless branch.include? 'game' # NOTE: Skip dead branches.
end

def fetch_node(node)
  if node.include? 'great'
    puts "LEAF URL: #{@leaf_url}"
    exit # NOTE: Stop checking once the leaf is found.
  else
    branch(node, 'right')
    branch(node, 'left')
  end
end

start = response('/challenge')
root = response("#{start['start']}")

fetch_node(root)