#functions go here

def yes_no(question):

    """checks user responce to a question is yes / no (y/n), returns 'yes' or 'no' """

    while True:

        response = input(question).lower()

        # check the user says yes / no/y/n
        if response == "yes" or response == "y" or response == "Yes" or response == "YES":
            return "yes"
        elif response == "no" or response == "n" or response == "No" or response == "NO":
            return "no"
        else:
            print("please answer yes or no ")

def instructions():
    """prints instructions"""

    print("""instructions""")



def int_check():
    """Checks users enter an integer more than / equal to 13"""

    error = "Please enter an integer more then / equal to 13."

    while True:
        try:
            response = int(input("what is the game goal? "))

            if response < 13:
                print(error)
            else:
                return response

        except ValueError:
            print(error)

#main routine

#ask the user if they want instructions (check they say yes / no
want_instructions = yes_no("Do you want to see the instructions? ")

# Display the instructions if the user wants to see them...
if want_instructions == "yes":
    instructions()

print()
game_goal = int_check()
print(game_goal)