Creatures Caves

On one hand, there'd be the Selective Force Field which can be configured who may pass and who not, by clicking... I think on the base? Not exactly sure, it's a while ago I used it last. The only problem is that very rarely creatures can slip through, but it only happens when you have a very big horde running relentlessly into it over and over again.

Next up, the Electric Wall. By far the most convincing and efficient method of blocking off areas. This is the only one creatures will believe is a legit wall, so they can not see objects behind it. The downsides are that while it does work in a lot of spaces, it does not work *everywhere*. Also, it has no filter system. It blocks off for everyone. I think it even blocks off for non-creature objects, like critters or plant seeds...

This Force Field again has no selection, but it's also rather effective and even can be used for one-way passageways.

Lastly, my personal favorite, the Norngarden Potted Stopperplant. Again, sadly no distinction between different creatures, but it can be put up literally anywhere and no creatures slip through, guaranteed.
Also, while is called a potted plant, it will not actually die or something. It just looks like a plant.