bad_guess doesn't append when I get wrong letter

import random

words = [
         'apple',
         'banana',
         'orange',
         'coconut',
         'strawberry',
         'lime',
         'grapefruit',
         'lemon',
         'kumquat',
         'blueberry',
         'melon'
         ]

while True:
    start = input('Press enter/return to start, or enter Q to quit')
    if start.lower() == 'q':
        break

    secret_word = random.choice(words)
    bad_guesses = []
    good_guesses = []

    while len(bad_guesses) < 7 and len(good_guesses) != len(list(secret_word)):

        for letter in secret_word:
            if letter in good_guesses:
                print(letter, end='')
            else:
                print('_', end='')

        print('')
        print('Strikes: {}/7'.format(len(bad_guesses)))
        #print(bad_guesses)a
        print('')

        guess = input("Guess a letter: ").lower()

        if len(guess) != 1:
            print('You can only guess a single letter!')
            continue
        elif guess in bad_guesses or guess in good_guesses:
            print('You already guess that letter!')
            continue
        elif not guess.isalpha():
            print('You can only guess letters!')
            continue

        if guess in secret_word:
            good_guesses.append(guess)
            if len(good_guesses) == len(list(secret_word)):
                print('You win! the word was {}.'.format(secret_word))
                break
            else:
                bad_guesses.append(guess)

    else:
        print('You didn\'t guess it! My secret word was {}'.format(secret_word))