In the MarsNAliens Black Hole Defence game there are many different types of aliens on the attack. They are powerful and strong but if you have a good tower defense strategy you will be able to survive the attack. The aliens are trying to escape by making it to a black hole and its up to you to stop them using your tower and turret defenses. You have a lot of different types of towers, turrets and other defenses to use so make sure you use them wisely.