# Check that users have entered a valid
# option based on a list
def string_checker(question, valid_ans=("yes", "no")):
    error = f"Please enter a valid option from the following list: {valid_ans}"

    while True:

        # Get user response and make sure it's lowercase
        user_response = input(question).lower()

        for item in valid_ans:
            # check if the user response is a word in the list
            if item == user_response:
                return item

            # check if the user response is a word in the list
            # the first letter of an item in the list
            elif user_response == item[0]:
                return item

        # print error if user does not enter something that is valid
        print(error)
        print()

# Displays instructions
def instructions():
    print("""
*** Instructions ***

This is a math quiz that contains basic arithmetic questions. 
Although you may choose to include area questions if you wish to.
Each arithmetic question will use two random numbers 
and a random operator (+, -, * or /).
For area questions it will either be for a square or rectangle.
The lengths and width will be shown for rectangles, squares will show one side with a number

Your goal is to answer each question correctly.

How it works:
• Choose how many questions you want to answer 
• You may choose if you want to include area questions or not.
• For each round, a new maths question will appear.
• Type your answer and press <enter>.
• The quiz will tell you if you are correct or incorrect.
• If you entered an incorrect answer, the correct answer will be shown.
• Your total score will be shown at the end if you wish to see them.


Rules:
• Arithmetic numbers are between 2 and 12.
• Area numbers are between 2 and 24.
• If area questions are included there will be a 50% chance for an
 area question to appear each round.
• For area questions you do not need to include units.
• Division questions may produce decimal answers.
• If an answer contains decimals it will be rounded to 1 dp.
• You can exit the quiz at any time by typing 'xxx'.


Good luck!
""")


# Main routine

# ask the user if they want to see instructions and display
# them if requested
want_instructions = string_checker("Do you want to see instructions? ")

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

print()
print("program continues")