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.
Making Time for a Little Life on the ZX81
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.
Writing a Utility Program for the ZX81 Was Such Fun
Sometimes, you do things out of necessity. I spent an inordinate amount of time working on adding automatic scrolling to a PRINT command. In fact, I haver another version of my print scroll routine I’ll talk about later. But this is about a utility program. A way to print out BASIC code in hex. And this article is about what I did and why.
Infinite Scrolling on the ZX81 with Machine Code Magic
Finding inspiration again from my programming groups, the idea of an infinitely scrolling screen of text came up. There were a couple of different solutions posted, some quite ingenious. I had done something similar in the past, but this time I used a bit of machine code magic to create a more flexible solution. The result is Print Scroll.
Meow in Motion: A Z80 Assembly Version of a Classic Cat Animation on the ZX81
After finishing the basic version of the cat animation, I wanted to improve the frame speed. This meant converting from BASIC to machine code. My first thought was to do the conversion with MCODER II. I dropped that idea, deciding to focus on a custom z80 Assembly version. Ergo, cat written in assembly or Fast Cat is, well, a faster version and a bit more.
Building a Star for a Vintage Computer
I missed the Dec 26 deadline for submitting, but did get a star working on the ZX81. My attempt isn’t spectacular, but it does work. I recommend checking out the other entries for Vintage Christmas Star Challenge.
More Isometric Fun with Scrolling on the ZX81
My frist isometric test was with a static background. Although that works well, it limits the size of the playfield. Thus, I decided to expand the playfield and scroll it around the player instead. It ended up being a lot more complex than I expected.
A Little Isometric Fun for the ZX81
Looking at various ideas for retro style games, something I’ve been wanting to try has been isometric graphics. I have a pretty good hand on tile based graphics now and wondered if I could do something similar with an isometric set. Hunkering down, here is how my testing is going.
More Mandelbrot Set Fun in Z80 Assembly
Okay, after finishing my BASIC program version of Mandelbrot Sets, I decided I needed more speed. I wasn’t sure if I could write a version in assembly. My concern was the floating point math. After a good amount of research, and trial and error, I finally got a version working. This is my story.
Let’s Cook up a Faster Graphic Enlarger for the ZX81
I haven’t had much time for programming the last few months. To get back into things, I decided to take an old BASIC program of mine and rewrite it. Thinking about what to convert, my mind immediately went to Enlarger. It was a rather slow animation demo that could use an update.
A Developer Diary in Pictures for Gem Quest, a ZX81 RPG
If you’ve been following me the last couple of months, you know I’ve been revisiting Gem Quest. Intended to be an Ultima style game for the ZX81, outside of a few demo’s I really hadn’t gotten far. That isn’t the case now. I’ve spent the last month learning z80 assembly code and hacking my way through the game. Tracking my progress, I’ve been capturing that journey in pictures and movies, which I’ve uploaded into a Flickr album.