The goal seems to create a "chain" effect and multiply your microbes in the dish. Disks eat quads and vice versa, but they all reproduce with the same pollen. Don't get all enzymes, some of them actually work against you at first. I recommend getting pollinate and cultivate so you can reproduce disks and quads, try to get rid of some herbivores if they start eating everything by using "harvest" or "mutate to plant". If you have enough plants in the dish, herbivores will actually help them reproduce. Fungi will also help keeping herbivores from over-multiplying. The hardest part is not letting either disks or quads be extinct, in that case just terminate the tests. You won't profit any further if you don't have both components present (you need both to form nuggets). Hope that helps!
I wish I could at least pick which microbes to place in my dish. All plants keep getting eaten before I can even reach the cultivate button to attempt to reproduce them. Some of the enzymes seem to actually work against me and I can't get rid of them. I really like the concept of this game, but took me a long while to figure out what the goal is (as others have pointed out), and I miss a "discard" button. For those asking for a speed button, it wouldn't matter. Your goal isn't waiting for everything to die out; if you have no more microbes left to place, no more enzymes and either quads or disks are extinct, you won't make any more profit out of it and you can end all tests.
Tips for those with difficulties: 1) Remember to check all locations. Some later levels unlock more locations and your suspect might be hiding somewhere else! 2) When you lose, check the actual "guilty" person so you learn what the traits mean (long face, football shape, etc). 3) Try solving the first one or two levels without using AP so you save some "cushion" for later levels. I promise it gets easier as you know what the descriptions mean. I'm not a native english speaker so it didn't come naturally to me.
For all of you wondering, all achievements are a reference to a different western movie :). "The Ox-Bow Incident", "The Horse Whisperer", "Cowboys and Aliens", "A Fistful of Dollars", "Blazing Saddles", "The Good, the Bad and the Ugly", ??? (I'm missing this achievement), "The Killer Inside me" and "Django Unchained". As a huge fan of the genre, thanks to the developers for this great touch :) Makes trying to find all endings super exciting for me. 5/5 and fav'd.
Too bad this game will be overlooked because of its lack of badges. This is one of those hidden pearls on Kongregate: after so many years of gaming, finding this one was refreshing. Thank you, meetreen_games! 5/5 and a favorite.
 "Petri Dish"){kind=icon}
 "Welcome to Winkletown"){kind=icon}
 "'Til Cows Tear Us Apart"){kind=icon}
 "Long Way"){kind=icon}