TLDR; the game is fine...
Can’t complain about performance. (iPhone 7+) When that’s said, it’s very repetitive once you get into mid-end game material. It’s very, very, grindy. And the auto-play is often a better player than yourself. A plus would be that it’s not very gacha (random poll loot; what you want to call it) you can buy each hero in game instead of using thousands of diamonds in summon without getting what you wanted. It’s definitely rewarding enough to be F2P, but I would think it would be less grindy for P2W. Which is always sad in any game - because there ultimately will be a power struggle between payed and non-payed.
