Well, that’s wonderful. Now I’ve missed two posting deadlines in 2018… but at least the year is right first time in this post and I have something of an excuse too, the house has been turned upside down over the last month and a half so the heating could be upgraded. I’ve only just got myself a desktop – and more importantly, a desk – up and running in the last couple of days so my thrown together “work environment” currently looks like this:
With nowhere to actually sit down and work – and more pressing matters like making space for various engineers to work – it’s been quiet on that front to the point where the “planned” post that was going to appear yesterday has been postponed. It’ll probably turn up next Friday when there’s more time available.
One thing that turned up whilst moving storage boxes around was the little A4 whiteboard used to plan for Retro Gamer each month before that job was shifted over to a text file. The board itself wasn’t interesting until I turned it over to find the slightly smudged but still legible to do list for RG Rampage. And yes, my handwriting really is that horrific and pretty much always has been which is one of the reasons why I taught myself to type at the tender age of eleven.
RG Rampage is a platform-based collect ’em up which was put together over a couple of weeks for issue 100 of Retro Gamer magazine, where it appeared as a type-in listing. And, at least according to the changelog kept in the game’s original source file, the final build was on the 11th of January 2012 which was a day over six years ago and that doesn’t make me feel old and decrepit in the slightest! So let’s take a look at what’s going on “under the hood” – a more human-readable version of the source code and some work files have been pushed up to GitHub – in order keep the game under 3.9K uncompressed.
Most of the savings come from the graphics which are optimised in a couple of ways to keep the overall size down; the character set is just cloned from the C64’s ROM whilst skipping the third byte of each character to make it look different, whilst the platform tiles – sixteen characters in total with one more for the titles scroller – are copied into that same 2K block of character RAM. Similarly, any object which can point in either direction like the player or some of the drones is actually stored just the once in the sprite data where it’s looking to the right, with the flipped version being generated on starting up.
Another place where things are reasonably compact is the level data; each platform uses five bytes for X and Y start position, character pair, colour and width and an entire screen only needs about a hundred bytes in total when adding the player start position, enemy patrol data – basically just another five bytes per nasty saying which object to use and giving two sets of X and Y positions to track back and forth between – and a stream of coordinates for the pick-up items. The level layouts were rather arduously worked out on printed sheets because getting a bespoke editor done would’ve taken too long.
I couldn’t include music because it would’ve added too much to the program’s length, so my (t)rusty “Roundasound” engine was dragged out of storage and given a bit of a dusting down; this is pretty much the same routine which was used for Quota by Chris Young and, with some modifications from Sean Connolly, in Flair Software’s Turn ‘N’ Burn so if anyone fancies a laugh they can have a prod through the source code for that. The routine is almost painfully primitive looking back and there’s a far better version now which is the base of my Atari 8-bit sound routine too, but it was compact and did the job.
The final “trick” was creating a BASIC listing for publication which, to keep the chance of errors sneaking in to a minimum, was handled by a truly hacky piece of BlitzMax code that yanked the assembled binary file in, generated a simple checksum by adding all the bytes together and then wrote out a text file containing the game as DATA statements and a small BASIC program with a FOR/NEXT loop which the code out to memory. That text file could then be tested by copy/pasting the contents into a freshly-loaded emulator and, when everything was deemed complete, sent off for publishing.
When Darran asked me to produce a type-in for issue 100 it seemed like a fun thing to try programming but I honestly didn’t expect anybody to actually type it in! There were a few brave souls who surprised me though and, judging by the feedback, they seemed to enjoy the experience of playing it as well. Going back to RG Rampage this afternoon for the first time in a couple of years to grab screenshots, I can’t help feeling with the advantage of hindsight that the balancing was a little off – almost certainly due to the dash for the finishing line – but it still feels fun to play.
Oh dear… I’m forgetting to post again, aren’t I? But here we go because this is a special occasion; Retro Gamer issue 100 is now available and, rather than my regular homebrew section (which turns four in April 2012… suddenly I feel old!) there’s a game what I wrote called RG Rampage in there as a type-in! In fact, here’s a video of it running:
At the time of writing Issue 100 can be purchased over teh interwebs (I got mine at the local corner shop today as well) and I’ll update this post when a file version becomes available, either because the publishers have uploaded it or when someone finishes typing the thing in!
In “other news” whilst I’m here, I was in Kent a few weeks back to visit family and head over to Margate for GEEK 2012[mutters under breath about the name] where I had a great time, met up with assorted folks from the Retro Gamer forum, actually got a chance to play some games for a change and took a couple of photos – I’ll try to remember to write up a more thorough “report” or at least upload the piccies soon!