A 52-issue weekly partwork that built into a 1,600-page programming course spanning six machines at once, including the Spectrum — and buried inside it, a 22-part machine code epic almost nobody finished typing in.
Every Spectrum program you've ever typed says OUT 254 or IN 254. The ULA doesn't actually check for 254 — it barely checks anything at all. A tiny program proves it, live, on screen.
A single SCREEN$ file that displays a picture when loaded to the screen — and runs as Z80 machine code when loaded anywhere else. The code is literally visible as colours.