I found this when experimenting. A few things I noticed: Candles, buttons, ect. become 2 dimensional. Every block is double its width. You can only walk in a straight line, but you can by pass this using enderpearls. Another way is to saddle a happy ghast stand on it facing the opposite direction on which way you want to go and then spawn a chicken infront of you. This will launch you. The weirdest thing is that all blocks have no collision.