Fun little game, the follow mechanics worked really well. I felt like the red microbes were not so much "evil" as they were just competing for the same resources, they never seemed to want to take over the green territory and were always in defensive mode rather than offense. The level progression felt a little odd, since the red microbes weren't in the last couple levels, meaning you just grow your group and you're done, was hoping that the later levels had the red ones trying to take over your territory.
Great work overall!