Great concept, very bad execution. The method used by the game to mix auto battler and gacha is so stupid that I wonder how it got approved. Want to combine units to get a higher rarity unit? You need to obtain it from gacha or clear levels first. Want to use your newly acquired unit? Good luck combining your way up to it. Finally got the unit you wanted? It's gone in the next game. The auto battler aspect is fun. The gacha aspect is ok-ish. The whole game in a package is utterly rubbish.