'There's a lot of cool things that, if you think too hard about it, they should never have worked': Fallout 3's pathfinding system had to be completely reworked over several months to account for Liberty Prime, but it was worth it because he's 'awesome'

You may remember the march of Liberty Prime, a set piece from Fallout 3 where the massive communist-hating robot stampedes across the wasteland and terrorizes everything in his path. Even climactic moments like the faceoff against big bad Mehrunes Dagon in Oblivion, which released two years before Fallout 3, seem static compared to Prime; Dagon is big and all, but Prime trundles across the open world like any other NPC.

You might think it's as simple as dropping a 3D model into the world and letting him run around...