"In the Irata solar system lies the planet Stella. It is surrounded by an energy belt. In this belt there live space oysters. They make good food, so there are other outer space creatures living among them, that eat the oysters..."
The space oysters are headed your way. You must shoot them to reveal pearls. Collect the pearls and deposit them in the Pearls Zone. Defend you pearls from being stolen or destroyed by attacking enemies. Near the end of each level, you must destroy the Oystron by dropping bombs. There is also a warp phase where you must travel at high speed between space oysters and enemies.