game.rb

require 'sinatra'

before do
  content_type :txt
  @defeat = { rock: :scissors, paper: :rock, scissors: :paper }
  @throws = @defeat.keys
end

get '/throw/:type' do
  player_throw = params[:type].to_sym

  # delivers error if user does not pick a valid throw
  if [email protected]?(player_throw)
  halt 403, "You must throw one of the following: #{throws}"
  end

  # selects a random throw for the computer
  computer_throw = @throws.sample

  # compares throws and selects winner
  if player_throw == computer_throw
  "Whoa, jinx.  You tied with the computer.  Try again."
  elsif computer_throw == @defeat[player_throw]
  "Awesome.  As we know, #{player_throw} defeats #{computer_throw}."
  else
  "Hmm... #{computer_throw} unfortunately defeats #{player_throw}."
  end
end