Naac reminds me a little bit of Smash Tv. It is a pretty straightforward top down shooter that can be downloaded from the developers homepage. You start with a handgun and have to defeat all aliens that emerge from different sides of the screen. The game would be incredibly boring if it would not feature power ups, better weapons, different types of aliens and even boss aliens that require strategy to defeat. It is absolutely crucial that you pick up the power ups and better weapons when they emerge randomly on the screen. It would otherwise become impossible to defeat the hordes of aliens at later stages.