- all-time high scorethe high score is reset every time player closes and restarts alien invasion fix this by writing the high score to file before calling sys exit(and reading the high score in when initializing its value in gamestats - refactoringlook for functions and methods that are doing more than one taskand refactor them to keep your code organized and efficient for examplemove some of the code in check_bullet_alien_collisions()which starts new level when the fleet of aliens has been destroyedto function called start_new_level(alsomove the four separate method calls in the __init__(method in scoreboard to method called prep_images(to shorten __init__(the prep_images(method could also help check_play_button(or start_game(if you've already refactored check_play_button(note before attempting to refactor the projectsee appendix to learn how to restore the project to working state if you introduce bugs while refactoring - expanding alien invasionthink of way to expand alien invasion for exampleyou could program the aliens to shoot bullets down at the ship or add shields for your ship to hide behindwhich can be destroyed by bullets from either side or use something like the pygame mixer module to add sound effects like explosions and shooting sounds summary in this you learned to build play button to start new game and how to detect mouse events and hide the cursor in active games you can use what you've learned to create other buttons in your gameslike help button to display instructions on how to play you also learned how to modify the speed of game as it progresseshow to implement progressive scoring systemand how to display information in textual and nontextual ways scoring