The laser needs energy to operate. This energy is always regenrating at a slow rate. Display Weapon energy is displayed in the upper left part of the console. Your score is displayed below the Weapons energy. The Radar in the center is showing all enemy ships.
Ships draining energy are red.
The remaining energy of the base is in the upper right part of the console. As soon as this energy reaches zero, the game is over. Here is your map of the sky, so you can plan out your strategies. Here is the view the aliens see as they are approaching. Here is your partner, he is watching from above and will send you information reagrding the enemys position.