In Slay the Spire after roughly 60 hours of gameplay I observed a well balanced gameplay loop of overcoming an enemy, dealing with risk/reward choices and stat/deck grow. 

Few times I was able to achieve an impactful snowballing effect (card synergies) and create three different builds with the same character (fast attacker, vampire-bite-healer, camper-buffer).

I felt a big difficulty spike in 3rd floor and an even a greater difficulty spike in 4th floor.

I am definitely the target audience, the game is fast, layered, difficult and addictive. I will delete it.