IDK if anyone still plays this, but to beat hard lure 2 biters to your base for the first 4 rounds and train/shoot them while your turret shoots them. Round 5-6 try and pick off a couple as you can while using the marine spawns to get them off your back. As soon as it gets too hairy. dump the aliens on the marines and book it to the very back of your base. Let the aliens tear down the bases as they have a massive amount of health and can take it. Save up enough money for the $4000 gun or even the $6000 gun if it looks like your base is holding. Run around killing the biters first until you get clear and upgrade armor then attack.
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