Logic is a optional system of blocks you may use to optimize your base. It's pretty easy to jump into Logic programming, and you can even use logic to stop thorium reactors from exploding!
I won't get too far into detail, but this is 99.99% of the reason Sandbox servers have gotten more attraction, especially since some people even made an entire chess game purely of Mindustry's logic system.
Just goes to show how crazy some people are to make crazy things.