Space Marauder

Space Marauder is a scrolling shooter, and has been compared to NES and SNES era shooter games such as Space Megaforce. The game puts the player in the role an infantryman dropped into an alien base that is determined to enslave humanity. There are three different power-ups, and the game allows you to shoot in eight different directions. However, due to the difficulty of switching the direction of fire during the midst of battle, it is regarded to be easier to just shoot in one direction. The three power-ups are considered standard for the genre: a blue bullet, a lighter blue laser, and a pink laser. The game uses a password system to continue progress.

Source: Wikipedia, "Space Marauder", available under the CC-BY-SA License.