The lack of a tutorial made it very difficult to understand what exactly I was doing, even after spreading decay all over the place I still had no clue if I was even winning or not. Also the game started to lag quite a lot once more and more tiles were active on the field at the same time, so it became difficult to continue to progress in the game. Other than that, I think the concept is sound, it just needs a bit more mechanical polish to really make it shine :)