Click the green flag Choose one out of Training, Regular, Horde, or Extreme. Training is where you have no life, aliens despawn when touched and you can practice the controls. Regular is the easiest with 3 lives and mild aliens. Horde is harder with 3 lives, but many aliens coming. And Extreme being the hardest with 1 life and a "billion" Aliens coming at you. Use the Right arrow or "A" and Left arrow or "D" to turn. Use the Up arrow or "W" and Down arrow to move forwards and backwards. You start out with a fast cannon and if you click 2 then you switch to a really slow, but powerful cannon. And 3 is a cannon And only if you play EXTREME you can click 4 to fire a straight laser that does MASSIVE damage. 1=fast(but pretty weak) 2=Slow(but powerful) 3= Cannon (Straight through enemies) To shoot the Aliens click Space or left click. If you touch an Alien you lose a life. Obviously, if you lose 3 lives you are dead and you have to click the green flag again to try again. (Hearts are displayed at the top)