Magic card "guessing" game

magic.rb

#!/usr/bin/env ruby
deck = (1..21).to_a.shuffle

show_deck = -> {
  n = 0
  deck.each_slice(7) { |pile| puts "\npile #{n+=1}\n\n#{pile.join("\n")}\n\n" }
}

select_pile = -> pile {
  piles = *deck.each_slice(7)
  deck = ((0..2).to_a - [pile])
    .insert(1, pile)
    .map { |i| piles[i] }
    .flatten
}

deal = -> {
  deck = (1..21)
    .each_slice(3)
    .reduce(&:zip)
    .flatten
    .reduce([]) {|result, i| result << deck[i-1]; result}
}

get_pile = -> { print "pile ? "; gets().to_i }

puts <<-EOL
pick a number in a pile, once chosen answer which pile it is in
3 times and I will tell you the number!"
EOL

3.times do
  show_deck.call
  pile = 0
  pile = get_pile.call until pile.between?(1, 3)
  select_pile.call(pile-1)
  deal.call
end

puts "Number is #{deck[10]}"