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!

2 thoughts on “Koalatro (C64)

  1. “Welcome back!”. The C64 world is a better place when TMR is active! Plus I get the chance to get some of my ‘stuff’ released periodically… ;)

    I’m obviously no coder, although I understand most concepts, but it seems to me that some people on CSDb didn’t understand the ‘purpose’ of Koalatro. i.e. the ‘trickery’ going on behind the scenes as opposed to what appears on screen. I’m referring mainly to the dull sod (or TMR hater!) who voted the ‘5’ score. I’ll have to ask Moloch who that was… ;)

  2. i’ll be surprised if i have a “hater”, i don’t think i actually interact with people enough to warrant one?!

    But if you don’t get what’s going on in the background for those scrollers or the juggling being done to cram everything into 15K then it probably just looks like another bitmap/scroller with a little sideborder use so i can sort of understand a five vote.

Leave a Reply

Your email address will not be published. Required fields are marked *