Workprint – July 2017

July 12th, 2017 by Jason

Yes I’m running late with the workprint post again (or perhaps I should say “as usual”) but, now that I’ve settled back into playing with game code, there’s been some time over the last couple of weeks spent dabbling with Z80 and quite a bit of head scratching about how to do software sprites; I’ve got a sort of working routine on the Spectrum which lacks proper X movement right now, but a lot more thought is required because it can only deal with three or at a push four objects per frame that are ten by ten pixels. That’s crappy and I know the problem is down to my Z80 “skills” being tragically weak, although another project that shall remain nameless for the moment has recently taught me a few things that might help.

On the 6502 front, I’ve been doing a few tweaks to Hammer Down that have been pending for ages so that’s slowly creeping forwards. There’s also the option of doing a small, reasonably well documented C64 game perhaps under the Backward Engineering label (since it hasn’t seen action for a while) to release via C64CD but I haven’t decided what exactly. My “default setting” is a scrolling shooter of course and part of me is tempted to write something with a simplified attack wave engine similar to the one in Ash & Dave’s Pirates In Hyperspace where the enemies have speed values for X and Y which all get changed when a timer expires. C64CD releases are meant to be simple so should I boil the design down to the bare minimum like that or do something a little more involved I wonder? Again, further mental gymnastics are needed…

MD201706 (accelerated C64)

June 30th, 2017 by Jason

Another release so soon? MD201706 is merely a plotter with some cosmetic niceness, but the code is a little unusual; it needs a SuperCPU (which can be emulated in recent versions of VICE and, unless it’s lying, it should run on either PAL or NTSC) or the Turbo Chameleon set to 6MHz or faster in order to run. Its single buffered and can clear, update and draw four hundred points a frame courtesy of the expansion hardware. It isn’t fully using the capacity of either device, the current firmware of Chameleon with its speed set to “no limit” is slightly faster than the SuperCPU but I restricted myself to 6MHz in case that top speed changes downwards with future updates.

A few people are probably going to ask “why” and the simple answer is “because”, but I’d actually been prodding around my unrolled plotter which was used in MD201704 on the C128, using 2MHz mode in the borders and found myself wondering just what my Turbo Chameleon could do with it. Then Wolf 3D for the SuperCPU arrived and I decided to make my code run with both. As always, GitHub is the source for… erm, the source and questions can be passed on in the usual manner.

This is probably going to be the end of season two for the Monthly Demo series because I want to take a little break to work on games… and yes, I’m already braced for the influx of responses that’ll probably get, so will be running away before this post goes out!

WannaClone (C64 and Atari 8-bit)

June 20th, 2017 by Jason

Two releases for the price of one this time, although they’re built on the same block of scroller code. WannaCrypt for the C64 and Atari 8-bit is a teensy demo with a loose copy of the WannaCrypt decryption tool and a scrolling message which is, due to a discussion about simple encryption at the Atari Age forums, reversibly mangled using a couple of simple techniques. Here’s the C64 version which features an old but still golden tune composed by Marc “Skywave” Francois…

…and this is what it looks like on the Atari 8-bit with graphical help from José Pereira and accompanied by Miker on the POKEY. There are even vertical colour splits being used on this one!

The source code for both the C64 and Atari 8-bit versions are available at GitHub, although they don’t come with the painfully hacky BlitzMax tool which takes some text and creates a mashed up binary file.