After many testing, the drop of virus cores were less, so I boosted the rate in the last minute. I was between two decision "too few that will hinder the player experience or too much that might be waste but at least the player can build the structure). I took the first decision.
That's actually a good idea, to turn loss into new source of strength as building, originally I wanted the player to have new moves as you lose the core structure indicating that the energy in human body (it's technically that as story with imagination) and be redirected to the player instead (white blood cell), but I had two constraints : time and lack of art.
I'm glad you have enjoyed the game.