That showcase video is great at showing both what is so fascinating about this program and - if you have had at as long as some of us - how the program itself has improved.
There's been an uptake in users recently, which is great! So I wanted to say "hi" to anyone who's getting started and offer some advice to (hopefully) prevent some frustration as you try to get evolution off the ground in your sim.
Firstly: Environmental settings are a big deal! Mutation rates, food spawning, and breeding requirements can all make a big difference in how easy it is for species to evolve, both initially starting from scratch and in terms of continually "improving" without degenerating into extinction.
If you're starting from scratch with totally random critters, by far the biggest impact is the frequency of food. You'll probably want a high food spawn limit so that basically just swimming forward is going to land food in a Critter's belly. BUT once things kick off, you'll want to gradually adjust this so that food becomes rarer and Critters need to learn better behaviors.
Another tip: If you're interested in trying to evolve predation, I've found the single biggest factor in evolving this behavior is high value plant food. The default value of 60 per nugget is usually not going to be enough -- Critters will evolve to use every crumb of energy, so if their usual meal is too much energy to fit inside their "bellies" they will either evolve bigger bodies, or more versatile "stomachs" (i.e. Omnivorous instead of Herbivorous.)
Finally, if you want to jump start your evolution with some Critters who already have a proven track record, you can try some species evolved in my own simulations by downloading them here. (Risatsirus Roseus in particular, if added to any simulation, will most likely become the dominant species in just a generation or two. They are EXPERT visual navigators and will evolve to chase down and eat anything, including other Critters, with very little prodding.)
Good luck, and have fun! Feel free to share any interesting things you discover on the Community Page!