The chest system at the end of each stage is pure bullshit. Most likely the chances are something like 99% to get the garbage item, 0.8% to get the next most garbage item, and then 0.2% chance to get the rare/epic item. If you use 7 karats to choose again, the chances probably go to 99% second most garbage item, 1% rare item.
Other than that and the extreme amount of IAP crap they have in this game, it wouldnt be so bad. I could deal with the rest if they didnt rig the chances of getting the shittiest items possible.
Open one of those gold/premium chests, and youll most likely get gold. This IAP business model really sucks, i wish a company would just step up and make a good game where you pay money up front and then not again. Or at least make it fair.
Deleting this trash, and id recommend to avoid this game. IAP is only OK when done right.