“Agent 51, your goal is within reach, but there is a problem.” “Understand,” you reply. Professional as always, you only allow a hint of annoyance in your voice. “Explain.” “Well, the plans are in the room in front of you, but the floor is a trap. You need to deactivate it using the terminal to your right.” You look down at the screen, a singular “READY” stares back at you. “Sounds easy enough,” you reply. “It isn’t. The interface is protected and, sadly, our operative died before he could tell us the code.” “So what do I do?” “You’re going to have to hack it. Our operative left a back door into the system, if you can find it. You can do it, Agent 51.” You nod at the voice in your ear. You can do this. Play begins with imagination. Computers are great for role playing and Code IV was one of my programs that helped enable a story. As a kid, I often augmented my play using my ZX81. Although the narrative above isn’t exact, it embodies what I was thinking when I wrote this month’s ZX81 program. Fun, adventurous, and unfair, can you crack the code and disable the floor?