For December, I decided to embrace the Christmas spirit. Inspired by group posts, I created a Christmas tree and snow scene. It needed a little flair, so I added an animated message to the scene. Very retro program for my ZX81.
ZX81 Prototype: Echoes from the Tower of Love
I've talked about Tower of Love before, but that was a much different version of the game. That version was all about the intro screen and my initial attempt at the story. I even showed another design I had made. To my surprise, I had a third version of the adventure that I started. Time to share!
Beyond the Atari: A Pitfall! Simulator for the ZX81
Pitfall! without the peril, with this accurate ZX81 simulator.--> While contemplating what ZX81 program to write about this month, I completely forgot that I had created a Pitfall! Simulator. It began as a fun project to occupy my time during winter break. My initial goal was to recreate David Crane's LSFR (Linear Feedback Shift Register) in Z80. However, after learning more about its functionality, I took the project much further than I had originally intended.
A Trip Down Memory Lane: Recreating “I Was Here” in ZX81 BASIC
A recently posted meme reminded me of the silly things we did on computers. In the early eighties, most computers came with BASIC as their default OS. A common starting point was a s simple “hello world” program. But almost as often, someone wrote something a bit more personal. This is my tribute program to the “I was here” concept of those days.
How to Create an Infinite Maze on the ZX81
I saw the Commodore 64 maze generator for years, but ignored it on my ZX81 for different reasons. For one, the characters needed didn’t exist on the ZX81 keyboard. The other was the lack of automatic scroll. Undeterred this month, I created my own version in Sinclair BASIC. I’m quite happy with the results, even if not quite the same.
Journey's End: Unleashing My ZX81 Split Graphic Mandelbrot Program
In my final article about Mandelbrot sets, I’m sharing the hybrid program built from the last two. After finishing the chunky graphics version, I envisioned a merged version. This split graphic version is a nice compromise to showcase the beauty of the fractal.
Chunky Graphics for the ZX81: A New Way to See the Mandelbrot Set
After completing my Chunk Graphics mode, my thoughts went to how best to use it. My first idea was something new, such as a flight simulator. After pondering, I stuck with something current by modifying my Mandelbrot Set program. With three gradients, it would be an interesting use of the mode.
Exploring Chunky Graphics: A New 3-Color Screen Mode for ZX81
Out on a run back in November of last year, I had this idea to create a 3-color screen mode of the ZX81. The idea was to use the checkered, or gray, graphic characters to add a third color. After reading about the C64 color modes, I called it chunky graphics as an homage to its wide pixel format. The pixel’s are chunky due to the 2x1 ratio and not being square. Let’s dig into the details.
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.
ZX81 Digital Rain: A Retro Display of the Matrix Code
![ZX81 Rain, Chroma ZX81 Screenshot, 2023 by Steven Reid]](https://www.reids4fun.com/images/zx81/zx81rain-2023-zx81-chroma-screenshot-by-steven-reid-320x240.png)
The holiday's provided me a nice break to enjoy writing code. During that time, I revisited my digital rain program. For ZX81 Rain, I cleaned up the colors and added a little randomness to where the drops start. Nothing super exciting, but the overall effect is much nicer and looked good in both black/white and color on the ZX81.
Accelerating FizzBuzz on the ZX81: A Basic Guide to High-Speed Integer Printing
Reading some old programming books from the eighties, I saw that the ZX81 had an ABS command that made me think I could improve my FizzBuzz program. It was late and my mind mixed that command with a modulus one, which the ZX81 doesn’t have. In any case, it offered me an excuse to fix the latency introduced by printing numbers.
Playing With BASIC by Revisiting My Retro E.T. Game for the ZX81
I had this idea the other day. One of the problems I’ve had with the ZX81 is printing numbers, which is pretty slow. Due to this, many of my games avoided printing them. delaying showing score until after play has ended. My idea was to try to find a way to speed that up. Not only did I find a way, I decided to implement it in an older game of mine: E.T.
Cat’s Can Be Fun on Computers Too
A recent post in a Facebook BASIC group of a cat animation. A couple of other members converted it to their BASIC code of choice. Mine being the ZX81, I promptly worked on a version for it. I created a mostly full screen version, which tends to show how slow the ZX81 really was. In any case, it was quite a fun little exercise.
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.
Let’s Have Fun Playing Snake on the ZX81
I’ve been on a retro computing binge lately and was recently watching one on programming on what it was like to program in the 80’s. Having lived and programmed during that time, I know full well what that was like. But the narrator was showing off an Apple ][+, a computer I didn’t own. Although I programmed on an Apple ][ in high school, my memory of it is vague at best. But what was really interesting was what he was programming: a snake game. Being something I’d never tried myself, I thought now would be as good time as any.
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.
A little BASIC fun with Mandelbrot Sets
Fun with Mandelbrot sets. I never thought I’d say that, but here I am doing just that on the ZX81. I ran across some fun discussions on them. They are often used as benchmarks, but I just wanted to create some interesting pictures. This is my version using Sinclair BASIC that creates a few interesting ones.
Creating a Fun Little ZX81 Implementation of Fizzbuzz
Hey, it’s October. Well, it has been for a few weeks now. In any case, it is also time for a ZX81 program. I recently joined an 8-Bit Programming & Engineering Facebook group and its cover is a photo of a FizzBuzz program in Pascal. As a quick exercise, I thought I’d write my own in ZX81 BASIC.
Wasting Time Watching Circles in This ZX81 Demo
I ran across a ZX81 forum post showing a fast way to print a circle in BASIC. It was based on an article for the Atari back in 1983. I was surprised how fast the routine was and wondered how it would in assembly. Long story short, I built a screen saver for the ZX81. Sure, the ZX81 really didn’t need one, but the circles are fun to watch.
A Super Fast Scrolling Demo on the ZX81
Totally divergence from working on Gem Quest. I got around to cleaning up my scrolling demo from last month. In doing so, it made me wonder would it would be like to code it in assembly. The answer is both bland and interesting. Let’s discuss why that is.
Super Simple ZX81 Scrolling Example
Although I've been busy working with the ZX81 this month, it has been with my Gem Quest game. Not much to share yet there, but I am working on it. To get in something for the month, I thought I’d share an updated demo program.
The Monster From the Deep Arrives on Your ZX81
This month’s program is a super simple graphic program I created in 1984 called The Monster. Probably developed as a title screen, the graphic looks like some swamp creature with seaweed hanging off it. I’m not positive what I was going for, but it does look rather imposing.
Wandering Down the ZX81 Road
I had this idea on Sunday that led to today’s program—more about that in a minute. One of those sit down and do it programs, I banged this out pretty quick yesterday. Not wasting time, I decided today I’d share it. Road is a very simple program that I never intended to make. But here it is, so lets talk about it more.