Katharsis is a game with classic side-scrolling shooter gameplay. It has 3D backgrounds, colorful graphics and an integrated storyline. The game starts in 2616, when the ship leaves Earth with 1000 settlers on board. Eighteen months later Earth loses contact with the ship. The action moves to the year 4720. One of Earth's cities is attacked by an unknown spacecraft. The player is one of the few survivors of the massacre.
The game consists of ten space levels and ten underwater levels where the player needs to protect a special bomb designed to destroy the enemy base. The player uses a whole arsenal of different weapons, can move in all directions and use afterburner. The fights with end-level bosses take place in full 3D environments.