I'm thinking about picking up a Game Boy Advance this week after reading about all the great games available over at ign.com. My one question is, what's the difference between a "cartridge save" and a "battery save"? Sometimes the reviews say one, sometimes the other and I find it a little confusing. I've never owned a handheld before, but I remember back in the old NES/Super NES days that saves were done on cartridges with a battery in them. Is this just two ways to say the same thing, or is there some sort of add on that I should plan on buying, like a memory card for the PS2?