In simplest terms your looking at a binary Calculator, least thats what i got out of it w. So he literally made a processor in a game.
Definition of ALU via wiki
In computing, an arithmetic logic unit (ALU) is a digital circuit that performs arithmetic and logical operations. The ALU is a fundamental building block of the central processing unit (CPU) of a computer, and even the simplest microprocessors contain one for purposes such as maintaining timers. The processors found inside modern CPUs and graphics processing units (GPUs) accommodate very powerful and very complex ALUs; a single component may contain a number of ALUs.
basically what i think i just saw was a caveman computer.