The premise is really good, but I found the interface confusing. I had no feedback which showed what the effect was of my actions. I place an entrence, and a bar appeared. What does that mean? I couldn't figure out. I bought three units, placed them in a room, and the sprites jumped around before disapearing. I did not notice weather or not I gained any money. Nor could I glance whether things were going well. I eventually died because suddenly my three uits, who were at full health, got overwelmed and died.
It is thus a bit confusing, and overwhelming. There are many different stats, what do they mean? How does rarity come into play. I got a SR, is that special, I don't know.
What let me most down was the lack of direction. I had no real goal, except making money to make more money. That works in an idle game, because you can't die, but somehow I had to prepare myself for what was comming next without having any idea about that.
Still, amazing idea. Amazing result for three days of work, and I hope that you work on this further.