you are correct. having to pay for membership is the conciquence of an ad free game.
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actually, you will be able to mix and match the 4 basic units to produce new units such as hurricane, which is air+water, lava, which is fire+earth, and ent, which is earth+water (I think).also, air elementals can shoot lightning! and there is a separate earth miner which is not shown.also, lava can burrow underground, ent can create small plants which can move, hurricane moves fast and can pick up stuff and throw it. all of the basic 4 elementals can also sacrifice themselves for a gigantic effect. earth will act like a spearton, air like an albowtross, fire like a swordwrath, and water like an archidon. the miners look like lizards/spiders however. I personally think that hurricane is the best. as for the mix and matching, I think that you highligh the two elementals you want to combine and press a button. I don't think that combining uses gold. the result is stronger than the the two elementals you used to put it together. also, combining water and fire produces a huge explosion which deals gigantic damage. water can also freeze into icicles or empty onto the ground and put itself together later. this slows down approaching enemies. there is also some sort of flaming lizard produced by 2 fire elementals. you can watch elementals fighting order empire in this video uploaded by crazy jay at youtube by searching for elemental empire stick empires on youtube (I do not know the exact address). It will be the first result you see. I hope this has made things clearer to you and has convinced you that it is an excellent empire.
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yes, it can.