In survival mode your task is to defend base as long as possible (classic Tower Defence Game concept). Difficulty is gradually increasing. In verison 1.80.23 ever-increasing number of Megatitans appear every 15 minutes, but no other types of Boss Titans. The Megatitans and also regular Titans have always increased hitpoints and speed in every conseqentual wave. Regular Titans are only Earth, Moon and Mars based. In older versions one Boss Titan appeares every 10 minutes, always stronger Boss. After fifth Boss (Ultratitan) the whole cycle of Boss Titans is repeated.
On the beggining of game you choose your planet, small/medium/large map, and percentage of mountains on the map. The crystals appear during first minutes of gameplay, but then the new one are created time-to-time on random positions only when some of the previous crystrals were refined. In older versions after depleting of one crystal the Refinery continued mining of other crystal only if the Refinery existed before that crystal. Avaliable technologies are based on technologies reached during the last level of Campaign in choosen planet. Also Easy Campaign counts if last level of choosen planet wasn't finnished in ordinary Campaign.
The barricades and mines (if researched on appropriate point of Campaign) can player obtain only in similar way as powerups and during Boss Titan attack basic stock is renewed. Some buildings in Survival Mode are more useful as in Campaign. For example robotics buildings and maybe refining improvement buildings.