There's only two options when making a Christian game.
A ) Making it cheesy and preachy and hyperspiritualized. Basic graphics. The type many here have suggested. Best suited for 50-somethings and 5 year olds. And no Non-Christians would want to get near.
B ) Don't make it Christian, but based off of some Christian concepts, that are stretched to not be accurate.
That's the problem with Christian movies and video games. There's really no room in the middle. But I think it's even more true for games.
Either way you can't really represent evil without someone getting offended. So if you do a good vs evil game, how do you create an immersive bad guy?
It's like this old Christian movie from the 90s, about boxing. Kind of a Rocky ripoff actually. But they wanted to paint the bad character clearly and the only way to do that was show him being bad. So insert the scenes of the rich, famous bad guy on his private jet, drinking alcohol with a woman in a tight dress on each arm. And other such portrayals, which then offended many Christians, especially those that took their children to see the movie.
So you can't do that, thus you have to just talk about him and what a bad guy he is, which looses something in the storytelling.
Hence the only option left are things which would be best suited as a game for phones that's "relaxing".