What I can only describe as some form of microscopic fart-cannon, the free and open source evolution sim Thrive has added what they call a Mucilage Jet for your creatures in version 0.5.10.
Yes, it's basically a way for you to add a way for your tiny little creatures to fart out a substance that gives you a burst of speed, and slows down other organisms caught in the mucilage. Thrive definitely sounds like it's starting to add more fun gameplay elements to it, while still being based on real science.
Another big new feature is time-based reproduction. Making the game a little more flexible, you don't need to constantly gather compounds as now all cells will passively acquire the necessary compounds over a period of time. This means even bigger slower creatures will always be able to do something and you spend less time mindlessly hunting for resources. To go along with this, you cannot just instantly reproduce when you have the right amount of resources, as it now takes time for it to be used.
They've also added a fancy new "Auto-Evo Exploration Tool", letting you run various auto-evolution generations with defined metrics and then you can dive into it directly to explore. Pretty cool. See more in the trailer: