There’s been a bit of a debate about how to categorise Charlie Brooker’s latest creation, the Black Mirror film Bandersnatch. Is it a film? Is it a game? With interactive choices that decide the actions of the characters, it’s hard to tell. What some particularly inquisitive viewers have found, though, is that there definitely is a game hidden at the end of Bandersnatch.

A loading noise made by a ZX Spectrum, the computer used by the show’s protagonist Stefan (whose life people have been ruining with their choices) can be heard at the end of the film. Some people immediately recognised this as the sound made by code being played back on cassette tapes and, on further investigation, it turned out that – with a bit of conversion – it could be downloaded onto the console and actually played.

The game that appeared was Nohzdhyve, one being worked on in Bandersnatch by the famous coder Colin Ritman. Since the discovery, game developer Matt Wescott has actually admitted that he was responsible for the easter egg (in the real world).

Read Wescott’s whole process (and a bit of extra Bandersnatch info) below.