NULLBYTE

A machine-code puzzle

NULLBYTE is a PC puzzle game about finding a one-byte mistake in someone else’s program and using it to make the program do something it wasn’t written to do. You work with a small fictional machine rather than real computers, reading its code and changing how it runs.

Reading the machine

The machine fits on one screen: 256 cells of memory, four registers and a stack. Its memory is visible as the code runs, alongside the stack and your input. The listing disassembles that memory in real time, so changing a byte can change the instruction you see. Bytes that came from your input are lit up, making it possible to trace their effect.