Great port of the all time classic. I think you have done a fantastic tribute to one of my all time favourite arcade classics. I always loved Space Invaders as a child. I do have a suggestion for a future update if you are able to update it in the foreseeable future. There is one screen missing, which is the score advance table, featuring the aliens and the scores per alien shot. Perhaps you could place this before the menu, and pressing fire jumps to the menu with the game options.