I saw this game at the reduced price and picked it up with my Google Rewards credit. It plays very nicely and has a just-one-more-iness to it. Uses very little battery, no ads, and no microtransactions that I can see. hex-based roguelike, reminds me of another android game I have played called Hopalite.
edit My mistake, there is in-game currency purchases, but they are not really in your face. In three sittings I have managed to earn about 400 coins fwiw.
That's the prove of 2-3 surveys. I'll give it a go.