Joey's U

Here is my Undo tile for Joey's Challenge. I nearly didn't make it in time, but I didn't want to miss out as I have managed all the other challenges since the alphabet started.

I don't really 'get' Undo. I realise after a couple of times you diverge, but then what? Do you keep diverging (I did) ? What happens to the space left behind, I went back and filled in with more aura lines, but is that right? Mine never ends up looking like the tile on the step out, that one has centre pools, when are they created? Any way, here we are:-