Belt decisions

Belts in the game are intended to be fast and flexible. There are no inserter-like entities and machines don't have designated input/output ports, so some early decisions were made. Belts should:

• auto-connect to machines when pointing directly at them, or directly away
• allow precise control of items while maintaining easy ad-hoc side-loading
• feel like rapidly sorting mail or luggage on real-world conveyors

Also they should have little shunting wheels and pop-up gates... because that's fun!

Straight belts are obvious:

Splitters will be familiar, although these have modes. Round Robin mode is the "normal" behaviour for distributing items evenly between outputs.

Overflow Divert mode delivers items straight ahead until the belt backs up, then diverts to the sides. Like a pressure relief valve. 

Each splitter output can be filtered or blocked. If an output is filtered then all items of the filtered type must exit that way, while the unfiltered outputs will continue to operate normally for other items.

Launchers throw items to Catchers. These are like underground belts, however the target catcher does not need to have the same orientation as the launcher, and multiple launchers can target a single catcher. This saves space and allows for some different layouts.

Mergers have a configurable priority setting for the three input directions. Since the game already allows belt side-loading the merger is meant for the more complex layouts, such as input top-up valves (opposite of the splitter's overflow relief valve).