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I don& #39;t use Twitter very often, but for a few days now I& #39;ve wanted to share my "quarantine project" 
https://abs.twimg.com/emoji/v2/... draggable="false" alt="😆" title="Smiling face with open mouth and tightly-closed eyes" aria-label="Emoji: Smiling face with open mouth and tightly-closed eyes"> This project is about an old MSDOS game I love: Supaplex.
This project is about an old MSDOS game I love: Supaplex." title="I don& #39;t use Twitter very often, but for a few days now I& #39;ve wanted to share my "quarantine project" https://abs.twimg.com/emoji/v2/... draggable="false" alt="😆" title="Smiling face with open mouth and tightly-closed eyes" aria-label="Emoji: Smiling face with open mouth and tightly-closed eyes"> This project is about an old MSDOS game I love: Supaplex." class="img-responsive" style="max-width:100%;"/>
Last year I ported another old game to Nintendo Switch: Triplane Turmoil ( https://github.com/sergiou87/triplane-turmoil).">https://github.com/sergiou87... Luckily there was already a port to SDL 1.2. It just needed an upgrade to SDL 2 and a few fixes! It was fun, so I wanted to port other games from my childhood
However, I couldn& #39;t find the source code of any of them. I tried reaching the original authors of those games, but no luck, so I gave up and went back to other hobbies. Then, this year, with COVID-19 around the corner in Spain, I got the "itch" again for porting an old game…
I found an interesting project about Supaplex: https://github.com/cilliemalan/supaplex
It">https://github.com/cilliemal... was "an effort to disassemble and understand the speed fix code once again". It already had a few symbols renamed, a few comments. Enough to get me started, but still feel like a challenge.
It">https://github.com/cilliemal... was "an effort to disassemble and understand the speed fix code once again". It already had a few symbols renamed, a few comments. Enough to get me started, but still feel like a challenge.
My goal was different: I wanted the C code of the game, reimplement all the input/graphics/audio code in SDL and make it open source and available for any platform we want. All that using the original game data files.
So at the beginning of March I just started working on it!
So at the beginning of March I just started working on it!
The first 2 weeks were just about translating asm code blindly to C in Sublime Text. I couldn& #39;t run or build that code, of course. My intention was to get enough translated until I got something "useful" I could see on the screen, when I could see my first bitmap.
When I was close to that, I just created an Xcode project and linked SDL to be ready for it.
I got a bit stuck because VGA code in x86 asm is painful, so I tried to reverse-engineer the bitmap format of the game data files instead and assume that just drawing that bitmap on the screen is enough https://abs.twimg.com/emoji/v2/... draggable="false" alt="😂" title="Face with tears of joy" aria-label="Emoji: Face with tears of joy">
In a first naive approach to decode those bitmaps, I found that they had the original image in 4 columns. Later I understood how to combine them to get the image I was looking for.
Yes, the colors were wrong. I hadn& #39;t sorted out color palettes yethttps://abs.twimg.com/emoji/v2/... draggable="false" alt="😅" title="Smiling face with open mouth and cold sweat" aria-label="Emoji: Smiling face with open mouth and cold sweat">
Yes, the colors were wrong. I hadn& #39;t sorted out color palettes yet
" title="In a first naive approach to decode those bitmaps, I found that they had the original image in 4 columns. Later I understood how to combine them to get the image I was looking for.Yes, the colors were wrong. I hadn& #39;t sorted out color palettes yet https://abs.twimg.com/emoji/v2/... draggable="false" alt="😅" title="Smiling face with open mouth and cold sweat" aria-label="Emoji: Smiling face with open mouth and cold sweat">">
" title="In a first naive approach to decode those bitmaps, I found that they had the original image in 4 columns. Later I understood how to combine them to get the image I was looking for.Yes, the colors were wrong. I hadn& #39;t sorted out color palettes yet https://abs.twimg.com/emoji/v2/... draggable="false" alt="😅" title="Smiling face with open mouth and cold sweat" aria-label="Emoji: Smiling face with open mouth and cold sweat">">
A bit more of work and finally I got my first bitmap on the screen!
Then I got palette transitions for fade in/out and other nice effects and finalized the "intro sequence".
After that I started working on the main menu. With that I would need to reverse-engineer mouse/keyboard input, many file formats, more graphics code… Took me around a week to have it all working!
The next step was the actual game. In the end it& #39;s an engine that you feed with levels, and it Just Works™. I started reverse-engineering the level file format and how to draw it on the screen… but everything was static.
It took me 2 weeks of more blind work to get something moving around. Two whole weeks translating procedures of 1,000-2,000 lines of asm code to C without being able to run or build that code. Painful. But… I was able to move Murphy around! Finally!
Then I fixed the animations, reimplemented some basic interaction with the environment…
Then reimplemented bomb and infotrons physics, explosions…
And with another week of work I finished reimplementing all physics and AIs of the game (mostly, at least), fixed many bugs and I was able to finish a level!
During all this process I used the awesome DOSBox debugger to either understand what the original code does or to make sure my reimplementation does the same when I found a bug. Breakpoints, step over/into, examine any part of the code/data… super powerful!! https://abs.twimg.com/emoji/v2/... draggable="false" alt="🙇♂️" title="Man bowing deeply" aria-label="Emoji: Man bowing deeply">https://abs.twimg.com/emoji/v2/... draggable="false" alt="🙇♂️" title="Man bowing deeply" aria-label="Emoji: Man bowing deeply">https://abs.twimg.com/emoji/v2/... draggable="false" alt="🙇♂️" title="Man bowing deeply" aria-label="Emoji: Man bowing deeply">
https://abs.twimg.com/emoji/v2/... draggable="false" alt="🙇♂️" title="Man bowing deeply" aria-label="Emoji: Man bowing deeply">https://abs.twimg.com/emoji/v2/... draggable="false" alt="🙇♂️" title="Man bowing deeply" aria-label="Emoji: Man bowing deeply">" title="During all this process I used the awesome DOSBox debugger to either understand what the original code does or to make sure my reimplementation does the same when I found a bug. Breakpoints, step over/into, examine any part of the code/data… super powerful!! https://abs.twimg.com/emoji/v2/... draggable="false" alt="🙇♂️" title="Man bowing deeply" aria-label="Emoji: Man bowing deeply">https://abs.twimg.com/emoji/v2/... draggable="false" alt="🙇♂️" title="Man bowing deeply" aria-label="Emoji: Man bowing deeply">https://abs.twimg.com/emoji/v2/... draggable="false" alt="🙇♂️" title="Man bowing deeply" aria-label="Emoji: Man bowing deeply">" class="img-responsive" style="max-width:100%;"/>
Other times I would just make small changes in the original asm code (mainly commenting out procedure calls) from cilliemalan& #39;s repo, rebuild it with TASM, and see the effects my changes had. That helped me understand the purpose of parts of the code.
Finally, I was in a position to do what I was looking for. And that& #39;s how I finally ported it to PS Vita…
…and Nintendo Switch! https://abs.twimg.com/emoji/v2/... draggable="false" alt="🎉" title="Party popper" aria-label="Emoji: Party popper"> Builds for both platforms are generated automagically thanks to a couple of GitHub Actions (https://abs.twimg.com/emoji/v2/... draggable="false" alt="❤️" title="Red heart" aria-label="Emoji: Red heart">).
All this work is open source and available at https://github.com/sergiou87/open-supaplex
If">https://github.com/sergiou87... you like it, pleasehttps://abs.twimg.com/emoji/v2/... draggable="false" alt="⭐️" title="Medium star" aria-label="Emoji: Medium star"> my repo!
If">https://github.com/sergiou87... you like it, please
Next steps: finish reimplementing the rest of the game https://abs.twimg.com/emoji/v2/... draggable="false" alt="😂" title="Face with tears of joy" aria-label="Emoji: Face with tears of joy"> specially getting the music and sound effects working. That& #39;s gonna be fun!
