Creative director of Irrational Games, Ken Levine talks us through Bioshock Infinite's sky-lines in a new dev diary. The sky-lines are golden transport rails that link Columbia's floating buildings, and can be traversed using sky-hooks. While riding the rails you'll be able to sky-shoot people with powerful sky-guns from the sky until they are dead. The footage we've seen so far has consisted of very scripted sequences, so it's hard to know how free-form Bioshock Infinite's sky-line battles will be. Still, the in-game action that is shown looks spectacular. Learn more in the E3 2011 trailer , or have a read of our Bioshock Infinite E3 impressions .