ZX81 Computer


Showcasing monthly programs, a retro look at my my first computer.
Water Bug Was My Attempt at a zx81 Action Game

For most of the day, Iíve been thinking about my Water Bug game as I never really gave it a proper write-up. Finally got around to playing it again, I was surprised to find elements in that I thought were unique to Water Bug II are actually in this version. That made me want to walk through each board, understanding better what I had done, what worked, and what didnít. Letís dive right in.

Posted 6 days ago by Steven 15 min read

An Early and Bad Attempt at a Yarsí Revenge on the ZX81

Like many teenagers in the early eighties, I was playing video games on my Atari VCS. Yarsí Revenge was a popular purchase, and I spent many hours dodging that stupid missile and trying to take down the shields of the Qotile. It then should come at no surprise that I tried to recreate that game at 13. My attempt on the ZX81 didnít look horrible, but it sure played bad. Letís see how much.

Posted Oct 31 by Steven 4 min read

Building a Better ZX81 Digital Rain using Z80 Assembler

My original plan was to create an z80 assembler version of Moon Lander. But with the trailer release for the next Matrix movie, I found myself revisiting another program. Built entirely in machine language, Z80 Digital Rain expands on my previous version with a splash of color. Let’s dive deeper.

Posted Sep 25 by Steven 8 min read

Amping up the Visuals and Gameplay in Moon Lander V2

Last month, I shared an old moon landing program I wrote back in the early 80s. Right after that, I decided to give it a bit of a face lift, updating the visuals without changing the game play. Moon Lander v2 is my updated game, yet still the same BASIC code under hood.

Posted Aug 21 by Steven 8 min read

Try Not to Crash the Moon Lander in This ZX81 Game

When I first started programming, one of the games we would play on the old teletype machines was a simple moon lander game. The premise is you would use your thrusters to softly land on the moon. Moon Lander was my take of that program a few years later.

Posted Jul 31 by Steven 6 min read

Your Imagination Is Required With Comp Control for the ZX81

As a young teenager, I often wrote programs that I would integrate into other play. In this case, I had probably watched War Games again. The idea of a computer talking to you made for some fun fantasy play. Comp Control a little pretend play where my lowly ZX81 mimicked a much more sophisticated world. Iím sure I was running around my room thinking up some crazy way to save the world.

Posted Jun 24 by Steven 7 min read

Trying My Hand at Animation by Moving a Sailboat on My ZX81

I was hoping to have finished Gem Quest by now, but May didnít afford much time. With Summer arriving and the pandemic seeming to be winding down, at least in Boise, my attention is elsewhere. With a short list of ideas, I decided to play off last month's theme. Picture in Motion isnít new, but it is more interesting to watch.

Posted May 31 by Steven 5 min read

Having Fun Learning How to Draw Lines on My ZX81

When Simeon Dwyer shared his machine language line drawing routine, I immediately thought of redoing ďThe Picture.Ē Most of my z80 assembly has been with my Gem Quest game. I decided it would be a nice diversion to work on something else, even if a quick one. Picture Asm is the result of that diversion.

Posted Apr 30 by Steven 6 min read

Not My Best Try at Programming an Ultima Clone

Iíve talked about ZX-Ultima before. It was first attempt at building an Ultima like game on the ZX81 using BASIC. Written in 2012, it was a pretty ambitious project for me. I really enjoyed playing Ultima III on my C64 as a teenager. I always wondered what it would look like on my ZX81. It was bad. Yet, at the same time you could see the seeds of what would come later.

Posted Mar 31 by Steven 5 min read

A Developer Diary in Pictures for Gem Quest, a ZX81 RPG

If youíve been following me the last couple of months, you know Iíve been revisiting Gem Quest. Intended to be an Ultima style game for the ZX81, outside of a few demoís I really hadnít gotten far. That isnít the case now. Iíve spent the last month learning z80 assembly code and hacking my way through the game. Tracking my progress, Iíve been capturing that journey in pictures and movies, which Iíve uploaded into a Flickr album.

Posted Mar 07 by Steven 8 min read

How to Build a ZX81 Ultima Game Part 2: Gem Quest

After sharing Tiles, I started to dig into my previous attempts at building an adventure game. Digging through my past research, I thought about encoding the world differently. Sadly, my experiments using MCODER failed. This spurred me to try assembler again and, to my surprise, build a good start to my game. But first, a trip down memory lane and review my first attempt at building Gem Quest.

Posted Feb 25 by Steven 6 min read

How to Build a ZX81 Ultima Game

In 2012 I wanted to see if I could make an Ultima style game on the ZX81. I had an ambitious plan centered on the tile based graphics. After a few months of testing, I was able to create a working prototype called Tiles. Although the game isnít done, the idea behind it shows promise. You can move around the map using the standard ASDW movements. Other commands are placeholders for what could be. This article explores how Tiles came to be.

Posted Jan 31 by Steven 10 min read

How I Used My ZX81 to Draw the Iconic OP Logo

As 2020 wound down, I had a couple of different ideas for new ZX81 programs. Most of them were graphic programs of various sorts. Themes ranged from dumpster fire pictures, an advent calendar, a virus action game, to a solo RPG. Although they were all great ideas, I didn’t think I’d get any complete enough to publish. In the end, I decided to enter in one of my old graphic programs of the Ocean Pacific logo.

Posted Dec 27, 2020 by Steven 4 min read

Creating Charts on Your ZX81 Couldnít Be More Simple

As usual, I procrastinated a bit in finishing my ZX81 program for November. Between holidays, work, and NaNoWriMo, I didnít get around to it until this last weekend. I decided to try something a little different for this monthís program. The program itself, Charts, is a simple line graph plotteróspelling and bugs galore. As interesting as that program is, the real story is how I entered it.

Posted Nov 30, 2020 by Steven 7 min read

Entering a Program Shouldn't Be This Frustrating

Back in July, I made a mistake and entered in Star Probe again. I had forgotten that Iíd already shared it. But, unlike my first attempt, I had taken a different approach which made it a much different game. Jumping ahead, I decided to finish what I started. Here is Star Probe Redo, an updated version as Octoberís program.

Posted Oct 25, 2020 by Steven 12 min read

Here Is a Silly Test Program for the ZX81

September proved to be a rather busy month, at work and home. It isnít unusual for me, and I usually find time to throw a render or program together. As this month closed, I found myself in need of a program to share and not a lot of time. While cleaning up a few things on my laptop, I found this little test program I wrote last month that fit the need.

Posted Sep 29, 2020 by Steven 3 min read

Here Is My Crazy Idea to Make a ZX81 Game with a Printer

Back in the day I learned to program on school PDP-11 with a 6 teletypes and a CRT attached. I was still in computer club at the time, thinking the 8" floppies were pretty cool. To my despair, the poor thing died that Summer and, when I took my programming class, it was on an Atari 800. But the programs I wrote the previous year stuck with me. Printer Car harkens back to those days.

Posted Aug 29, 2020 by Steven 8 min read

Can You Win in This Easy Game of ZX81 Dice

Lately, I’ve been reflecting on my programming journey. It is hard to believe that it has been over nine years since I started writing my monthly articles. I’m nearing the end of my printouts, and thought I’d write about my ZX81 Dice Game.

Posted Jul 31, 2020 by Steven 5 min read

Try to Be a Great Space Navigator Taking This Silly ZX81 Quiz

Having a healthy imagination and perchance for sci-fi, Spaceship is a bit of both. I assume I conjured up the idea as part of some playtime activity. Written in 1983, it was one of my earlier programs and lacked graphics. Yet, it was still a bit of fun.

Posted Jun 29, 2020 by Steven 5 min read

A Silly Little Code Hack For The ZX81

I have some sort of fascination with code breaking. A byproduct of all the spy movies I watched as a kid. A friend of my would make spy cases with Lego’s, and I had to build my own of course. I had a wallet with home made credentials and so on. Code Searcher is a bit of a homage to those golden age gadgets of the 60s and 70s.

Posted May 25, 2020 by Steven 5 min read

A Good Start To Adventure Game That Never Was

When I was a child, I remember going over to a friends house and playing Wizardry on his Apple. Leaving his house, I was super excited about the game I saw. Although my lowly ZX81 was no match, I had visions of creating my own games like it. My attempt, although a test, could have been so much more.

Posted Apr 28, 2020 by Steven 7 min read

It’s Not Easy Surviving the Waters in This ZX81 Game

A bit cliche by 1985, but I was obviously still playing Frogger and the clones it spawned. With all its dodging and moving, the game is classic for good reason. Even in modern times, it has spawned the likes of Crossy Road and other in spirt games. My own attempt, called Sea Cross, finds you trying to get your family safely across the water and home. I doubt you’ll be able to.

Posted Mar 29, 2020 by Steven 5 min read

Resurrecting an Old Band Logo in This ZX81 Animation

The ZX81ís graphics be a lot of fun to program. Although I wasnít a big fan of the PLOT command, I do have some examples of its use. My taken on the TS logo for the rock band Twisted Sister is one one example. Like a primitive screen saver, it can be fun to watch.

Posted Feb 27, 2020 by Steven 4 min read

Play an Old Star Trek Game That Fails to Be Fun

Okay, I’ll admit that I was a Star Trek junky. As a kid, I remember eagerly waiting each week to watch reruns of the original series with my family. When 1983 rolled around, I’d watched both of the original movies and owned the comic books that bridged the two. As such, creating a Star Trek game on my ZX81 should come as no surprise.

Posted Jan 25, 2020 by Steven 4 min read

Can You Run and Jump Your Way through This ZX81 Game?

Running platform games with simple controls were all the rage when mobile gaming got started. Although the themes varied, they all tended to have a few if only on control to them. Some made you press down and release. Others ran on their own, requiring you to press or swipe as needed. My journey into the genre began in 1985 when I wrote Bolder. It may not be popular or exciting, but does show that the concept had roots going deeper than you may realize.

Posted Dec 29, 2019 by Steven 6 min read