You suffer an attack on your desktop and you must defend building a structure buying guns with the money that you have. Attackers will go from one side of the screento another another. You must position the guns to shoot them and make them dissappear. With the money you earn you can buy guns more powerful and faster. Also when you acumulatte money you can sell the weapons less effective and buy better. Each attack you receive will be more powerful than the previous one so you must increase your defense.