Play the evil role this time as you are the alien invaders. Take your army of alien troops and air ships to destroy the defending cannon. The cannon will continuously fire on your herd of alien aircrafts and jets. Your mission is to retaliate and click on the jets facing the cannon. The jet will fire bullets and missiles towards the cannon. If you click on the jets behind other jets, the jets on the front may get destroyed. You cannot avoid the cannon fire, so destroy it before it takes down all of your alien jets. The more you fire at the cannon, the more the health bar will reduce.