Thanks for playing and advice! I'll edit the game following your advice.
The defence stat went from 1 to 0.95 because your soldier would take 95% damage instead of 100%. Sorry I didn't make that clear.
I'm really sorry, I did a poor job of conveying this information to the players. Upgrading Heart and obtaining mutations for heart both increase the maximum health value (and they multiply together). I didn't clearly communicate this mechanism, and it's such a shame that you lost your game for that. My bad!