Articles by Glen's Weblog

This demo shows that you don’t need to double buffer the screen if you know where the scan line is. You can draw your sprites where the scan line is not drawing. I’ve posted the source to my GitHub link … Continue reading → …

I was going to post about this topic while I was working on Defender but didn’t get around to it and since I’ve started working on Joust which has the same video hardware I’ve come across the same situation and … Continue reading → …

Hi All, I’ve been working on porting the arcade game Joust to the CoCo 3. I wasn’t going to discuss it until I actually got it working as I don’t want the project to end up like my Defender port. … Continue reading → …

Hi All, This post was spurred on because I was replying to a comment today where someone was asking for my z80 to 6809 program and the link was dead.  I updated the link to the latest version I could … Continue reading → …

Today I completed converting the Defender Arcade code to play through all three attract modes.  The last one was definitely the hardest as it contains the sprites moving around the screen.  I also had to convert how Defender draws the … Continue reading → …

Hello, I just wanted to document this neat little trick here.  For changing the colour of one of the 16 stars on screen randomly in Defender they do the following: * Table of stars @ $AF9D to $AFDC * Format … Continue reading → …

I’ve been working hard on the Defender conversion and am happy with the progress and how well things are going.  I uploaded a video on YouTube showing that I now have two out of three attract screens working.  The code … Continue reading → …

Hello, in a recent in post I got a comment from username Perezernestoj who asked if I could convert Super Pac Man as my next game for the CoCo after I complete Defender.  I explained how much work this is … Continue reading → …

Below are a couple of coding tricks I’ve learned from Defender this week.  I thought I’d pass along the tricks for others to use, if they aren’t already. For simple loop counting, a nice fast way is to load an … Continue reading → …

Just a little blog entry to share a neat little bit of 6809 code. I’m really impressed with how well the 6809 is programmed in Defender.  I was decoding some of the Defender source code today and I came across … Continue reading → …