Game engine recreation

Game engine recreations are remade engine interpreters for video games that replace the original engine binary that came with the original game. A notable example of game engine recreation is ScummVM which successfully recreated the SCUMM engine of classical LucasArts' point and click adventures. For further examples, refer to the list of game engine recreations.

Game engine recreations are made to allow the usage of classical games with newer operating system versions, recent hardware or even completely different operating systems than originally intended. Another motivation is the ability to fix engine bugs which is often hard or impossible with the original engines (with notable exceptions, see community patch) once a software has become unsupported abandonware, with the source code not available.

When game engine recreations are made in a top down development methodology, in the first step the general game's functionality is programmed and the structure is defined. Then, in later steps, the resulting engine is adapted to the specific detail behaviour of the original game, often by reverse engineering, debugging and profiling the originally. An example is OpenRA based on specifications contributed by the community by clean-room re-implementations without dis-assembling the original executable, which result in game engines whose behavior differs from the original. Another example is the Total Annihilation engine remake Spring Engine, which resulted in being used for many more games. Typically, this approach results in an approximation of the original behaviour only and not a "clock cycle wise" identical behaviour. On the positive side, running code exists faster and the finally resulting source code is less specifically tied to specific, single game and can be re-used as general game engine for other games.

...
Wikipedia