For once you are not going to have to save mankind from all of the endless names of enemies that are out there. You will be helping to save the Martians from the humans that are invading to make way for a second planet to inhabit. The humans are a very aggressive bunch and have destroyed the defenses of Mars and you are the last defense for your entire planet. What would you being saving if you are the last? It's not like you could restart your race unless your family is on vacation down in Star Cluster 2057. Anyways this does not matter all that matters is that you make sure to shoot the astonaut soldiers that will be attacking from your left and right. Make sure to watch your energy levels so your laser gun does not overheat. At the end of each round you will be able to use the currency you have gathered from battle to use to purchase upgrades for your gunner and for the resource gathering robots.