nice game and easy. The best is to repeat level one several times to have most effective upgrades (the machine-gun, grenadier, freezer and the platforms) then lunch your mine easy. In Earth after deploying grenadiers over platforms as first line, you could go to near by 7/11 and come back to see the end. Its fun simple game but even as it is easy, you still feel the challenge up to where you have the best upgrades then you will lose interest.
still I would grade it 4 stars.
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