Why is shadow the hedgehog so mean?

Oh, dude, Shadow the Hedgehog is like the grumpy teenager of the Sonic world. He's all moody and brooding because of his tragic past and stuff. I mean, if I had to deal with aliens and government experiments, I'd probably be a little cranky too. So, yeah, that's why Shadow is so mean, but hey, at least he looks cool doing it, right?