I am a complete newbie to screenwriting. I have settled on trying Celtx as my scriptwriting software as it seems pretty user friendly, easy to use, will auto format in the right style for me and, importantly, it's free! I can also access the Celtx Studio from my PC and my MacBook and from the iPad's Celtx Script app, allowing me to sync across all my machines. However, I am wondering what is a decent software to use for the plotting and planning phases. I am a very visual person and like things to look good and organised, so that would be awesome. I would like something where i ca plot the scenes, flow, developments, twists etc before i move on into writing the script. As I am using Celtx, which is free, I am willing to pay for the plotting software. Any suggestions?