Core War is a fictional competition between two programs running in a virtual machine. It was invented in 1984 by D. G. Jones and A. K. Dewdney. The competitors, or warriors as they were called in the original paper, are written in a simplified assembly language called Redcode and compete in an arena of 8,000 (some competitions choose 8,192) memory cells.

The goal of Core War, as in any war, is to destroy the opposition. A winner is declared when the all of the instances of the opposing program die by executing an invalid instruction.

This demonstration implements a Core war simulation on the Gopher Badge. Text, updates, markers as memory is read or written by a warrior, are written directly to the ST7789. While the action appears frantic, the overall amount of data to be updated per frame is relatively low. The average number of pixels changed per frame is around 7% so the overhead in drawing commands is offset by not maintaining a frame buffer where 93% of the image is unchanged per frame.

Left and right randomly choose a new respective warrior. Up and down increase and decrease the simulation speed. A pauses, B resets.

The demonstration includes victorious warriors from various Core War tournaments.

The code is available on GitHub, davecheney/corewar.