Pretty fun little autobattler gacha game! For as mindless and dumb as it can be, I had a surprisingly good time with this and ended up getting addicted to building up my army and watching them eviscerate enemies like a pack of piranhas. And as much as I say it's dumb, there is still a method to the madness where you need to decide how best to plan your gacha purchases around the rent time limits and so on. So yeah, nice stuff!
Having said that, there will a few rough spots I encountered:
*On my first playthrough, I kept just encountering slimes over and over until it got to the point where I couldn't earn enough money for rent. It wasn't until my second playthrough that suddenly I started encountering coffee cups and other higher tier enemies that could give me enough money to stay competitive. Maybe the spawn system could be better reworked to avoid this, or better yet, the spawn system could be removed and instead have different areas on the map where different tiers of enemies congregate that the player should move to as they get stronger? Might give it a bit of a journey/adventure feel where you're moving forward instead of running circles in the city: maybe you even need to pay to unlock the doors to these new biomes like COD Zombies to add more strategic elements.
*The game started to feel rather monotonous and unsatisfying as it went on as I don't think it delivered the sense of progression/evolution effectively. Compared to something like Vampire Survivors where you go from small stuff to thousands of bullets covering the screen later on, this game feels rather stagnant: the enemies change shape and the numbers are technically increasing, but everything "looks" the same. One change that I think would help would be the way money is handled: I was surprised when I started to get so much money later on because it didn't "look" like I was. Instead of only increasing the coin sizes like you do, maybe you should keep the size the same, but just spawn more coins: an explosion of 100 pennies looks more appealing than 4 quarters, if you catch my drift.