This video is StartCraft II - Co-op series using Karax to play like "Tower Defense" without producing units to fight.(still need some energizers and observers). I don't have a good skill to micro control units but I learn this trick of tower defense from other one I have played with in Oblivion Express. Now I have almost complete all Co-op achievements. |--| I want to leave some tricks for someone like me encounter difficulties to get achievements such as "Target Purified". |--| 1. You must have a good partner to help defensing enemy like baneling, broodlord, tanks, immortals and most importantly, attack Trains.(Karax's tower can't contribute too much damage to trains, they are used to clean enemy with trains). High land is very important, you can ask your partner to help to clean or using observer and Khaydarin Monolith to clean that. |--| 3. Second train will leave when time is about 8:00, you may wonder why I put Purifier Beam in a place without any enemy and control it to. This is the most important point to get the "Purifier Target" achievement, because enemy is always generated from that point..