Arcade
Humanity has expanded through the galaxy, thanks to crystals made of an unknown matter that provides high levels of energy, and they are used by all galactic civilizations. This energy matter appears as energized gems, to pick up the gems you will need first to take away the excess of energy by shooting them. When you kill an alien it will throw out his crystal so you can pick it up. Be careful because if you shoot a crystal it will be destroyed. Survive and collect gems!