Astro Warrior

The game is a basic top down shooter that was common at the time, similar to Zanac for the NES. The game plays through three levels with a boss at the end of each. Astro Warrior's three levels each have many different kinds of enemies that attack in various patterns. The stages themselves have no obstacles. Like most shooters, learning the enemies' patterns and how best to deal with them is the key to success in Astro Warrior. Also as important is collecting power-ups, which can be accomplished by shooting at targets on the ground. These power-ups are vital to the game as it is almost unplayable without them, especially the speed-ups. Without speed-ups, your ship moves way too slowly to do much of anything. The other power-ups include a stronger laser weapon and two Gradius-style options.

Source: Wikipedia, "Astro Warrior", available under the CC-BY-SA License.