This paper is a documentation of the design and implementation of an educational dungeon game created in HTML, CSS, JavaScript, and Three.js. The player is a character in a succession of three-dimensional rooms where one is required to fight enemies by answering questions and finding hidden chests with hints of knowledge. This way, they are expected to answer informatics questions to unlock exit doors. Errors send the player back to 'penalty paths' ensuring the importance of correct recall. Progressive learning content is gathered in an in-game journal, which aids in spaced repetition and memory retention. The design of the system, game mechanics, educational design rationale, and implementation details are fully discussed. The project is a proof-of-concept in the use of a browser-based 3D game environment as an excellent tool to teach computer science topics at the undergraduate level.