The key will help to open the door to the next level. You have a perfect gun helping to kill the enemies. You explore different locations where a key is hidden. INVASION - is the simplest 3D shooter with surviving elements in which you must survive on an unknown planet. Don't think it won't be hard. Every location is full of various aliens who want to destroy you. The main idea is simple. Collect ammos, medical kits, door keys, kill opponents. The game will be thrilling for you. Good luck. FE.
more information...