The game itself is fine. You auto-merge soul stones until you get two level 10 ones. Merge those together for a new hero (i.e. the gacha). It's a fun system.
I'm giving a low rating because Gamepub doesn't know how to handle app updates to save their life. Most apps will prompt you to update the game before you can even make it past the title screen. This game doesn't. So when I logged on today, I received ZERO idle rewards after idling for about 7 hours the previous night. I had the same 5b gold I had the night before. I tried to update and reopen the game to see if that would give me my idle rewards and still nothing.
If every other game can tell you to update before you play, why can't you all follow suit. I don't want to play an idle game where I don't get idle rewards because the devs can't program a simple "please update your app" screen. You already had an update 1 day after your play store release, so I wouldn't be surprised if this keeps happening every week. Fix the way you handle updates so your players don't suffer because of your mistakes.