Yesterday I was playing Battle Supremacy on my 13" cMBP, and all of a sudden the . . . game . . . began . . . to . . . lag, not terribly, but it was definitely not ordinary. I just thought that it was a bug, as I was playing online and was about to quit the game, but then the low battery notification/warning came up. Just a few minutes ago, the same thing occurred, with the battery warning appearing. So my question is, are MacBooks supposed to reduce their graphics performance when the battery reaches a "critically" low level? Thanks.