Oystron

Oystron is one of the earliest homebrew game for the Atari 2600. The project was started as a multi-sprite demo. The player controls a ship shown from a side view that can freely move around the fixed screen and can face both directions. Enemies called "space oysters" appear from the right and need to be shot to convert them into pearls that need to be collected before they leave the screen on the left side. Collecting is done by colliding with them, which transports them to a "pearl zone" on the left side of the screen marked by two vertical columns. The pearls are stored there, but can still be stolen by enemies when they pass.

The game tracks the score and a meter is filled at the bottom of the screen showing progress. There are four lives and a new one is provided for every 4,000 points. For every row of eight pearls a bomb is provided. At the end of a level an Oystron boss appears. It can only be defeated by putting a bomb in its path so it cannot get away. As soon as the boss appears a warp phase is entered and the player's ship travels at a fast speed, avoiding enemy collisions. There are three difficulty levels.