Shoot Em Up is a 1st Person Shooter where you control a target on the screen and shoot waves of aliens over various levels. You can scroll the screen left or right as you search for the aliens to shoot and once you have shot enough you move to the next level. The aliens will throw cubes at you and if one hits then you lose part of your shield gauge and when it reaches zero you lose one of three lives. Other gauges to keep an eye out for is your fuel gauge which slowly decreases and ammo which decreases when you fire. There are icons scattered around for all three gauges and when shot increase them.