"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"...
...so starts the documentation for this game by Piero Cavina. Apparently, Oystron was started as an exercise in Atari 2600 programming after investigating how to reuse a sprite to put more objects on the screen. "I don't care," you may shout, "tell me about the game!" Very well then...
Starting on the left hand side of the play area (you can move around the whole area) you manoeuvre your ship to a position where you can destroy the enemy, who approaches from the right. Shooting the Space Oysters with your missiles reveals a pearl. This should be collected and dropped in the Pearl Zone, defined by a line of white dots. Placing eight pearls in a row rewards you with a bomb for your ship. Failure to collect, results in some stray pearls morphing into more enemies. Some enemies who are not destroyed and who reach the left hand side of the play area seize your collected pearls - the pearls can be retrieved by shooting the enemy again.
Towards the end of the level, a signal is heard and the screen flashes: The Oystron (end of level "boss") is approaching! You no longer have the ability to fire missiles; you must use the bombs that you have collected to destroy him or you can avoid him and do nothing, waiting until he mutates into a standard Space Oyster but losing many bonus points in the process. At this stage you are transported to the Warp Phase where you must destroy enemies and Space Oysters at high speed in an attempt to boost your score. A new level then begins.
The title screen is an uncomplicated affair, just like the original arcade machines, with an endlessly running attract mode. Although blocky, the graphics in Oystron are very colourful and well defined and these solid visuals are backed by some satisfying and appropriate sound effects. But this game isn't about the title screen, graphics or sound; it's about furious shooting action and strategy.
Starting on one of three level settings (beginner, intermediate or expert) the control of your main ship is excellent; it moves very smoothly, the feeling of inertia being faultless. Pressing the button rapidly fires your missiles, but holding down the button produces a steady stream of them, incredibly welcome in a battle game! Furthermore, the fire button both drops pearls when in the Pearl Zone (your ship indicates when it is ready to do this by flashing) and drops bombs when the Oystron is approaching. Overall, good use has been made of the simple controller.
The enemies are intelligent and the many variations display different character and tactics that you must learn. For example, guard your pearls carefully. If you allow them to be stolen an enemy appears that cannot be destroyed, only driven from the play area with your missiles. Especially annoying when the action becomes intense!
For the first few plays you will become frustrated, even with four lives at the start. Trust me, persevere because you will be rewarded by an immensely playable and addictive game. Blasting everything is important (and fun), but soon it becomes apparent that formulating strategies to destroy individual enemies, collect pearls or even stay alive, is the order of the day. This gives Oystron immense depth and lastability.
Much like early arcade games, limited hardware and memory can be compensated for by intricacies in gameplay. It is obvious that the programmer has spent a great deal of time and effort in perfecting the game mechanics and playability and squashing it all into a measly four kilobytes. With aspects of both Space Invaders and Defender, as well as some new concepts of its own, Oystron is an initially hard but engrossing game. If you want a quick blast then this is not for you; if you want thoughtful blasting action then Oystron comes recommended. | 
