Playing FPS games on a mobile device with a controller isn't exactly black magic. Manufacturers have been scrambling to provide mobile players the greatest gaming controllers for their phones since since PUBG mobile and similar FPS titles were released for Android and iOS a few years ago.
While...
I want to say it's one to one, but in all honesty I'm a bit fuzzy there. I can recommend JoyFreak's sister site AdminIntel - Admin & Webmaster Resource where there are lots for people of varying degrees of expertise with development, you likely can get a far more precise answer there!