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If you open up the Life category on the left side and the Bacteria category on the right side, you can continually click the Bacteria category on/off and it makes the Life category send a smaller Life symbol out. So pretty much if you are stuck and waiting for your lightbulb, you have something to do! :)
Under rating threshold (hideshow)
Yep, I did enjoy trying to figure out which combinations did what, but I echo the others on that trying to find those last 20 or so combinations is a chore when you can't keep track of what you already tried. 4/5