ttons include one for basic shooting, and another for the different abilities you have.
As you complete levels and kill aliens, you start getting experience. As what usually happens in this type of game, earning experience helps you level up, and as you level up, you get special abilities.
Alien Zone Plus is an action game with some really entertaining touches of RPG, outstanding graphics, and a huge amount of content. You can unlock new characters, new space stations, weapons, etc.