Yes, this image is about the "holdout" mutation system.
You can play it by going on "Mutation" in the main menu, and select "change mutation", then select "holdout
There is also a "dash
" and "shootzones
" mutations that are part of the EMS.
After selecting the mutation, start a new game through menu.
Or if you want test directly, type e.g.
map c1m2_streets holdout
There is only a few maps with holdout mutation and you can also download some more on steamworkshop
Here is some:
In my opinion is a great mutation.
If you like it, you should try some "Let's Build Maps
" that was a similar approach.