Low quality ads and too few options
The ads are for low quality items and games. And getting longer and longer in time and complexity (meaning you have to click through more and more stages, wasting your time on bad ads.) The options / settings are too simple. For example, it allows turning off sound but does not allow have an option to reduce animation time. Positive point is no data is required to play. So one could turn off data to play without ads but you would not be able to access help options when stuck on a puzzle.