Koalatro (C64)

I’ve been almost worryingly quiet for a few months – according to others rather than myself I hasten to add, I worry about me all the time – due to a mixture of illness and… well, more illness really. Normal services will hopefully be resumed once the “festive season” is out of the way and I cheer up a bit! In the meantime, I’ve been working on entries for the Intro Creation Competition at the C64 Scene Database where the primary rule is that the releases must use a single block of 16K at all times. I’ve already put out one called Clonetro on the C64CD label and today has seen the launch of the second, this time from Cosine and sporting some music from aNdy.

Koalatro is a somewhat masochistic exercise in cramming a multicolour bitmap, music, scroller (with unrolled colour splitting code that takes over five hundred bytes on it’s own) and some text into just 15K. Using a Koalapainter format picture in an intro that small whilst executing doesn’t sound too complicated, but the 10,001 bytes of data would normally eat through two thirds of the space before any code or music is included! So, whilst all the data that a Koala picture would normally require is still present, 1,000 nybbles of $D800 colour data have been rather unceremoniously packed into 500 bytes. The double speed music (the player is called twice per frame) was supplied by aNdy who originally created it for a CSDb competition a few years ago, fortunately it was pretty short because the intro needed it to be.

The scroller started out as a reasonably straight copy of one in Contribution by Super Swap Sweden – the sprite colours are split on each scanline rather than the background colour, so it only just has enough time to load two values, write to all eight and keep the side borders open if the entire loop is unrolled and all of the LDAs are absolute! As is now usually the case, I’ve pushed the source code to Github for people to prod around, but it’s not exactly the cleanest thing I’ve ever written!

MD201606 – JSL Poop (C64)

I’m half a week behind with the post because… well life stuff again, but there was another new monthly demo released last Wednesday under the Cosine flag; it’s named MD201606 – JSL Poop because it uses a two and a bit screen high conversion of a JSL-drawn picture called CSDb Shit. It took a couple of days to convert the picture and clean it up so that the text was more legible, write the bitmap scrolling code and generally put everything together including a great last minute musical contribution from aNdy.

There’s been quite a bit of “scene drama” behind the picture; it was originally posted to Facebook by JSL for around twenty minutes until he decided to remove it but, social media being what it is, that was more than long enough for it to be downloaded and, a few hops later, there was the CSDb entry. The question of whether somthing like this counts as a C64 scene release has been raised in the comments there but, to my mind at least, it references people, a website and events within that scene so is perfectly valid even before we consider the C64 scene’s history of ragging images in paper-based magazines or on disk envelopes.

I was challenged over my actions and asked if I had a reason to hate JSL; the answer to that question is no I don’t and my primary motivation was the challenge of pushing the aforementioned image into the C64 and making it scroll, even if that proved to be far less difficult than I’d expected! But at the same time, JSL’s posting the original picture made a statement even if he wasn’t brave enough to stand by his guns afterwards, so in that respect MD201606 can probably be considered a tweak at his nose , albeit without much malice intended; perhaps it’ll serve as a reminder in future though, if he doesn’t want things he creates seen by others it’s best to not distribute them on the internet in the first place! There’s some source code I’ll possibly regret posting over at Github

The end of the war

Battle Eagle is finished and sent off a day before the ABBUC competition deadline! For those who haven’t read the previous posts, Battle Eagle is a vertically scrolling shoot ’em up that uses the Atari 8-bit’s 80×192 pixel sixteen shades of one hue graphics mode and hardware sprites which are horizontally expanded to make them fit in a bit more cleanly. Here’s a short video of the title page (with some of the music composed by Sascha “Der Luchs” Lubenow) and some of the first level:

Here are some “interesting” facts about Battle Eagle just because I’ve remembered how to do bullet points today:

  • It has 50FPS smooth scrolling using a character-based screen mode.
  • There are 60 screens of scrolling background constructed from 3,620 4×4 character tiles.
  • Up to four independently controlled enemies, all generated with just two hardware sprites.
  • There’s 106 frames of animation for the explosion, player ship and enemies in there.

At some point I’ll try to do another post mortem like the one written for Callisto last year but for the moment here are a couple of screenshots and the game itself will be released onto the Cosine website as soon as the nice ABBUC people give the okay.