Whichever honestly, mostly for multiplier because it gets ao hard to pick up that your score only goes up steadily after a point haha. You could add magnet for multiplier to the upgrade menu itself for further away and add a power that draws in other power ups maybe? If its balanced haha. Maybe add a score multiplier that gets expensive, go up in .1 amounts, gives people the chance to get good scores, or something that you can upgrade infinitely that wouldn't break the game but then currency would always have a use. Something needs to be done about the ships, the missiles never target mine and when there's 7 the bullets shoot slow so miss you at first and hit you later, it's great, but annoying on a good run haha