if you still want to create it, as long as you dont use the original Pokemon graphics, and you dont use the official game, logic/programming files(ie. js code etc) you cant be sued. ideas can be patented, however ideas that are made public, cant be called in a Law Court. as long as you do what i said above.
however this is not a official legal advice, you should contact an attorney and ask him, or contact Nintendo(as i recall if you contact them, they give you permission, as long as you also publish on their platforms, where you also get a % of the income.). the advice i suggested is from my own knowledge.