Total Annihilation is a great game.  It features a futuristic based gameplay setting with 2 races (Arm and Core).  When this game was released, the AI was something never seen before.  I was amazed to see that my aircraft would actually try and avoid enemy missiles and laser fire.  Units would fire while they were running.  There was also no limit on units to build...ok there was, but its like 1650 so don’t complain.  There were so many units, I loved it.  Then they released their expansion set (Core Contingency).  This set didn’t just add 6-7 units like most expansions do, but this added over 150 new units!  Plus you can download extra units from cavedog.com.  It is a great game, and even though its a few years old, it still looks great, plus its cheap, go and buy it now!