What is it Game Engine of Game like Simpsons Tapped out,Family Guy: The Quest for Stuff,....? [on hold]

i have a question what is it Simpsons Tapped out , Family Guy: The Quest for Stuff , SpongeBob Moves In , Clash of Clans , Boom beach , ... game engine? i believe someone say they have own engine but i think they use specified engine and customize that engine.is very important to know.i have a article in university for My phd and i don't must start from where.

P.S #1:if they don't have a specified engine please introduce me some useful article.

P.S #2:i think that engine is CrossPlatform,if that isn't,is not important article about what platform is it.