It is the time of the year again for me to embarrass myself. It is much harder to make a prediction this year than the last.
15 gas build is arguably one of the most popular builds now for TvT. It can transit into Marine Tank or mech composition. It basically works like a 1-1-1 build with an earlier command centre. Given that it is a 1-1-1 build, there are many things you can do early when the Medivac is out. This post discusses some of the better variations of a 15 gas build.