Alien Invasion is a challenging skill game on www.flash-games.net for free. The goal for you is to smash the enemies by shooting at them and protect yourself depending on the four stone shelters. In the game, left click launch the ammos to the enemy which is composed by many units. The units will attack you by throwing down the ammos too. Hide yourself under the stone shelters to avoid them. But the ammos will also damage the shelters eventually. So you have a rigid time limitation to clear all the enemy units before your shelters are totally destroyed. The war is crucial. Come on and good luck!