RUBBUR

An OldSkool Demo for Amiga OCS
Runs on Amiga 500 with 512k FastRAM and beyond.

Video on https://youtu.be/cc8f7zg3-v8

Written in hardware banging C, with a little pinch of assembler.
Compile with SAS-C on Amiga. (just run smake)
It uses PhxAss to compile the assembler parts.

Or cross-compile with vamos on osX or windows.

Released at RSYNC Demoparty 2026

You find the executable, ADF disk and MOD file in the "Release" folder.

I probably should include my full setup on the Amiga side, but for now: go find your (emulated) Amiga and install

• SAS/C compiler
• PhxAss assembler

-> navigate to the "rubbur" folder and run "smake" It builds the executable to the file "a"

Compilation is done on amiga, but you can also cross-compile with vamos on osX or windows. for that, you'll need to update the paths to your amiga files (where you put Sas/C and PhxAss) in the ".vamosrc" file.

The mod is included in the "release" folder. I use SplitMod to splt it into sample data and song data, so the song data can be loaded into Fast RAM.

• how to flip an image horizontally using code
• how to use functions in assembler to speed up operations and call them from C
• how to scroll a screen horizontally
• how to use vamos to run the SAS/C compiler on osX and windows
• I moved from shrinkler to cranker for compression. Shrinkler compresses better, but cranker is faster to decompress.
• in the end, I avoided compression alltogether. If all assets fit on a single floppy, it's simpeler and visualy nicer to keep them uncompressed.
• another thing I figured out but did't use, was how to use the assembler INCBIN thing to include binary data in the executable. Good to know if I ever want a single file demo. For now, the approach to have a light startup exe to display a loading screen and post-load the data is fine.

• get a hold of timing ... Sync is all over the place and behaves differently on different machines. No doubt my code is still too slow, but at the VERY least I should measure how many cycles each part of the code takes. This is the reason why most effects run a bit faster on a 1200. I beat-synced the thing to be in sync on my machine, but the timing will be slighty of on other machines. This sucks ... To be improved in the next production.