Not sure if this is already implemented, but in order to make it more challenging you could allow biters to traverse void tiles.

https://pastebin.com/ZnHtjA1u

It's a little hacky given that you have to re-add player collision in a different form, but it will let biters ignore void tiles.

Gods no.

Part of the attraction of this is it gives OCD-friendly chokepoints to defend.

Can always add it as an option, single chokepoints can make the game extremely easy and it may be unwanted.

Having to defend a potentially uneven front makes things interesting, especially since you could have one stretch of void knifing into your factory.

I'm working on some stuff to make that less of an issue.

It's been almost a month since I've heard from the author, so I'm forking to make my improvements.

@illiander42 -- do you mean the changes we discussed to the mangrove balance? I thought you were happy with what I proposed? I haven't implemented the changes yet, but I wasn't aware it was an urgent issue to need a rapid patch?

Or did you mean some other change I may have missed somewhere?

Regarding the original proposal to allow biters to traverse the maze, I'm afraid it doesn't seem possible. Artillery are somewhat fussy about collision masks it seems, so it conflicts with the terraforming. It's a shame, it'd be funny as an option!