Headcannon Game Engine (HCGE) is a multiplatform 2D game engine with focus on high performance on lower-end hardware and simple portability for the user. It has been in development solely by Simon "Stealth" Thomley since 2004 officially, though it has roots in his older work going as far back as 1997. The use of Headcode as its programming interface allows for development on one system and play on any other for which the engine exists without requiring the developer to (re)compile or make any technical modifications. It also has built-in editing tools that become more powerful with each update, and is the origin of the "live editing mode" featured in the Methyl game engine.