Logic tweak

Ok, we were supposed to work on the Game Off Jam but half of the team (me) is KO because of flu and we are a bit stuck at the game design phase; we have some ideas which are under HEAVY investigation now so I've had some minutes to spend on this little experiment.

Decided to remove a bit of randomness by making a plant poisonous after it blooms, this should make the game a bit more challenging; however, there is still a bit of randomness when the cow eats a plant and this opens the idea to increase the probability of generating a poisonous plant after N (with N to be decided) turns.