They both use unity, which is in my opinion the easiest to code engine currently on the market (if you ignore completely non-coding-engines like rpgmaker) Even though a platformer, with a similar way of fighting to pure onyx, like NOR is a bit harder to accomplish. Especially if the levels actually have to look good.
I bought up unity since he dos his own Hand drawn art that he drops into unity witch i now i a massive pain to do, He has a stream were he shows what hes up to sometimes and posts videos on Twitter its crazy watching him work. (talking about Night of Revenge NOT Eromancer dont AT me)