Gemstone Keeper is an action twin-stick roguelike shooter where a brave explorer can traverse a large and mystical cavern to search for rare and precious gemstones. The deeper an explorer goes into the caverns, the more valuable gemstones that can be found, however at the risk of facing more of the dangerous and hostile creatures that live there, including creatures that are larger than life.

Armed only with a gun, explorers must break through rocks to collect minerals and gemstones and fight off the creatures, and find the portal that can help them go back up to sell what they collect or go further down.

Gemstone Keeper uses ASCII art in both a pure and diverse form, as almost every part of the game's look come directly from text and symbols while very loose in form. The weapon and bullet system is fully interchangeable, over 150 gemstones to collect, several creatures and bosses, different game modes and a soundtrack that echoes through the open spaces in-between the rocky walls. Gemstone Keeper is the shooter that is both fun and eerie.