The key to getting most established game genres to work on mobile is to simplify.
Keep whittling down the experience, stripping away those unnecessary layers until you have something workable and fun.
The important thing to remember is to stop before you hit the game itself, at which point you'll just be carving away chunks of fun. That's when you get something like One Tap RPG.
As One Tap RPG's extended title states, it's an unlikely mash-up of the RPG genre and Pachinko. If you're unfamiliar with the Japanese parlour game, just replace Pachinko with Peggle and you'll get the gist of it.
So, you drop your little knight at the top of a dungeon infested with assorted monsters, pots, stones, and power-ups. Said knight proceeds to trundle down through this dungeon in a straight line.
When the knight encounters an object or monster, he'll bounce off, smashing or killing the obstruction in the process (and sustaining a hit in the case of armed enemies).
These obstacles render loot and experience points, as well as modifying the knight's path. Get to the end of the course and you'll either open a random chest or fall through and perish.
The trouble is, your interaction in the above scenario ended at "So, you drop your little knight at the top of a dungeon..."
Since the game was launched, the developer has responded to criticism by adding the ability to make your knight speed up by touching the screen, but essentially this remains a randomised physics demo rather than a game.
That could be bearable (at a stretch) if the rounds were a fast, kinetic joy of springy physics and mayhem. But they're not.
Rather, each level is a slow, boring trudge to a wholly unsatisfactory end and an arbitrary score. There are two modes, Normal and Daily. But they both involve the same non-gameplay, so there's really no notable distinction worth making.
With One Tap RPG, developer Tiny Touch Tales set to work whittling down the RPG in a commendably fresh fashion. But it cut away all but the barest hint of gameplay in the process, and that's proved fatal.