The new engine reads the old engine's files and, in theory, loads and understands its assets in a way that is indistinguishable from the original.
Game engine recreation is a type of video game engine remastering process wherein a new game engine is written from scratch as a clone of the original with the full ability to read the original game's data files.
See also: List of open-source video games § Open-source remakes with non-free content from the proprietary original
