Class hierarchy flattening is a project that I worked during the last five years. We try to remove type hierarchies and type information from Java programs by obfuscating them. See https://ieeexplore.ieee.org/document/6739076/ for the early results, we have new results on more recent Java versions with much lowered performance and code size overhead. This class hierarchy flattening can be seen as a delayering transformation, just like our library boundary obfuscations.