Beetee is still messing round the tree, doing I don't know...

Beetee is still messing round the tree, doing I don't know what. At one point he snaps off a sliver of bark, joins us, and throws it against the force field. It bounces back and lands on the ground, glowing. In a few moments it returns to its original color. "Well, that explains a lot," says Beetee. I look at Peeta and can't help biting my lip to keep from laughing since it explains absolutely nothing to anyone but Beetee.