GeoJelly is a demo version of the full-length, action, side-scrolling platformer of the same name. A player directs a golden-yellow blob through 15 of the dozens of levels that are normally available to help the character escape the laboratory where it was born and experimented upon by unknown evildoers.
The character can't walk. It's only capable of jumping in two directions. The dark laboratory is also full of obstacles and traps, including deep chasms, spike pits and serrated saws. There are also difficult-to-navigate cushions that make the blob bounce off floors and walls. Although these cushions can help it reach non-dangerous areas, they can also bounce it into bad situations. As a result, the player must move the character carefully through the many rooms.
The character can only enter another laboratory chamber via a portal at the end of a level. They must collect diamonds along the way. When the player completes a certain number of chambers successfully, the demo unlocks additional ones up to Chamber 15. The best part is that the demo provides the player with infinite lives. If the character dies in an explosion of smaller blobs and bubbles, the player never has to worry about buying or earning lives to replay the level.