Cool concept, I can see myself playing again and again, and definitely its not as easy as it looks lol. I thought that when timer reaches 0, virus will spread and game will over, but its nice that we get few more chance to clear the board and great thing about this mechanic is, that since it spreads with same color, it becomes more easier to remove, but there are more of them to remove, so it doesn't get too difficult but strikes perfect balance!!
Good game and great work