Your objective is to shoot the bad guys as accurately as possible. You can aim for the head or the body area. The closer you are to the center of each of these areas the more points you gain. The trick is to make every single shot count.
Snipe the snipers before they snipe you. Once you start shooting, the sniper timer will count down fast so you may want to try and remember their positions if you can. Watch out for the sneaky soldiers that move in and out of cover.
Keep your base safe from the huge advancing army using your trusty sniper rifle, air strikes and artillery. With each wave the invading army gets stronger, spend your money on the right upgrades and try to survive the war!