Solution: Counting to 21

puts("You and me take turns say a number, the player forced to say '21' loses. At each turn, player can increase the number 1 or 2.")
print("Do you want to go first? (y/n) ")
choice = gets.chomp

the_number = 0

if choice == "y"
    print("You (1 or 2): ")
    player_number = gets.chomp.to_i
    if player_number > the_number && player_number <= (the_number + 2)  
        the_number = player_number 
    else
        raise "Foul! You lose."
    end
end

while the_number <= 20
    # stategy
    my_next_number = my_next_number_1 = the_number + 1
    my_next_number_2 = the_number + 2
    if my_next_number_2 % 3 == 2
        my_next_number = my_next_number_2
    end

    puts(" Me: #{my_next_number}")
    the_number = my_next_number

    if the_number == 21
        break
    elsif the_number == 20
        print("You (#{the_number + 1}  :-( ): ")
    else
        print("You (#{the_number + 1} or #{the_number + 2}): ")
    end
    player_number = gets.chomp.to_i
    if player_number > the_number && player_number <= (the_number + 2)  
        the_number = player_number 
    else
        raise "Foul! You lose."
    end
end