I thought I’d try something a bit different this month. I’d been looking at different ways to build maps for years but never really did much with them. After watching a video on binary partitioning, I decided to see if I could build a simple map builder on the ZX81.
This is the result.
I wrote this back in August and I’m finally getting around to publishing it. It was first shared in my BASIC group, but the ZX81 lacks a lot of the functionality needed for it to run well. Undeterred, I hacked at the program to not only display the twisted cylinder, but also add a bit of randomness to the demo.
I’d seen a few different BASIC programs that print out a map of the world. Generally blocky, they still looked decent, but much of the data was too big for the ZX81—until I ran across a C64 version based on a Spectrum program. Examples in hand, I built a version for the ZX81.
Having finished my last Truchet tiles program in BASIC, I wondered how fast it would run in machine code. Soon afterward, I gave it a try, writing a version that runs significantly faster than the BASIC one. Let’s dive in and see how it works.
Sometimes ideas drop right into your lap. In the case of this month’s program, it was a mix of a post and a video that led me to this Truchet animation. A simple concept, but it worked way better on the ZX81 than I expected.
It’s funny how a random video can spark an idea. One moment I’m watching someone play around with ASCII art, and the next I’m thinking, “Hey, I could make something like that on the ZX81.” That little spark turned into a weekend project: a simple banner program using different fonts. How fun!
This month’s program is a bit of a departure. It is a take on the classic "Wolf, Goat, Cabbage" puzzle. The twist is, I didn’t write this one. Instead, I decided to update it to make the interface a bit easier to use. Let’s dive into the code.
With little time lately, I decided to explore some Generative AI ideas to flesh out new concepts. I’ve dabbled in vibe coding for some time now and thought I’d see how the models would do with adventure-style games. One of the results of that was Castle Quest, a small text adventure for the ZX81.
After updating my print scroll routine, I started thinking about how I could use it to create a different version of my infinite maze program. The original used graphic characters and spaces since the ZX81 lacked a backslash. This new version takes a different approach, using alternate graphics to build a more visually interesting maze while leveraging a better machine scrolling routine.
I’d read about and studied cellular automata but had never programmed any simulations for them. Conway’s Game of Life is the go-to simulation and something others had already implemented on the ZX81, even when I was a kid. I finally got around to typing in some of those programs but found them slow. My version aims to correct that.