This updated version of Alien Invasion now contains multiple levels. As you progress through the levels the background changes every so often, and game difficulty is increased gradually with enemies getting quicker and firing more rapidly. I am still trying to optimise the game difficulty, so I would appreciate any feedback regarding whether the game is currently too hard or easy. If you also have any opinions on how the gameplay could be improved further, please let me know as well.
My next objective is to attempt to create the High Score table. I have never previously managed to implement such a feature in any of my projects, but hopefully by doing a bit of research, I will be able to implement the High Score table before Christmas. Wish me luck!