"Space Guardian" Game

Time for a space shooter. As usual, save the earth before the aliens take control of. Laser fire is enabled instantly whenever an enemy is above you. Watch on your red health bar in the upper left corner. Whenever you are struck, your health reductions (and your score) more or less, depending on your damage. Change music and sound FX to your preference. Everything can be silenced. Can you beat all alien intruders?