Mrs is right. I considered writing for mobile but there are major hurdles to doing it. For one as a writer you want to be able to test things, and it's not easy (at least in most mobile games) to backtrack and try different options. Plus the uh, financial, hurdles so to speak. Imagine maxing everything and how long that'd take without dumping gobs of money into the app. For those reasons I haven't wanted to start such a thing, for fear I'd never be able to finish.
One last hurdle I saw were the frequent updates and events. It's a lot to cover, and your work could be rendered obsolete by an update.
I'll stick to writing on games where you pay your fee and have the right to play and cheat all you want