JTace is a purely HTML5/JS free and libre interactive fiction/text adventure creation engine. It's easy to use, easy to modify, flexible, and powerful. The engine was created by Ben Ehrlich for the development of Underground Dungeon. Features of the engine include robust natural language parsing, an integrated combat system, maze/labyrinth navigation, inventory and spell casting systems, a well commented, well organized code base, and an easy to use object oriented creation system.