COSCUP 2026 - Conference for Open Source Coders, Users, and Promoters

UXN is a stack-based virtual machine designed by the Hundred Rabbits. It's small enough to fit in a single C source file, and simple enough to be ported across a wide range of platforms, including GBA, Nintendo DS, DOS, PlayStation Vita, Raspberry Pi, and many more.

UXN is minimal but not limited. Paired with the Varvara devices, it can support games, drawing tools, editors, and even a graphical operating system.

UXN is simple and hackable, which makes it a useful way to learn the fundamentals of virtual machine design. This session will walk through the specification, including opcodes, memory layout, and device I/O, and then examine the reference implementation, uxn2.