Astroblaster

Astroblaster is a retro-style top down, single player, space shooter. Your mission is simple: Clear away the asteroid belt and the space pirates that have been using it for a hideaway.

Asteroids contain weapons that can help. Pirate ships leave behind vital raw material that can be used to produce a steadier supply of munitions. You also need to rescue astronauts who've been left adrift in space after pirate attacks. They can build weapons from the raw material.