I have no idea if there are people interested in pixely physics sandboxes here, but I am.
I'm a big fan of creating electronics in The Powder Toy (TPT) and one of the things I dabble in is lithium-based calculating devices. I previously made these 4 modules for the 4 basic operations: +-*/. But now I streamlined these modules, drew a pretty "enclosure" around them and made sure they're working without bugs. Also I made a sample device that calculates ((59+10) * 3) / (160-137) - if you wonder how it works, go install TPT and find out! It's free and fun.