Obfuscated C -- Sixel Starpath

Code

Here is the code: sp.c

Requirements

Ideally you will run the program in a shell that supports vt340 "sixel" support. Many shells do.

On a Debian Linux system at least your best bet is to run it inside of an xterm run with the following

    xterm -ti vt340

Alternately you can direct the output to a file and use ImageMagick but it will only show the first frame of the animation.

    ./prog > out.sixel
    display out.sixel

Obfuscation

Rather than going for intentional obfuscation, this entry is size-coded.

This is inspired by the size-optimization of Applesoft BASIC (and other 8-bit systems) that were done on a now sadly discontinued series of twitter-bots.

It turns out size-coding is often indistinguishable from obfuscation.

This was an attempt to take a program and make the source code as small as possible.

Some examples of things you can do:

Turn if/else constructs into ternary operator when possible
Re-use variables when possible
Move increments from loop headers out into the loop body
Avoid whitespace
Shrink constants when possible (Ironically tricks like 1e4 instead of 10000 don't work as well in C as they do in BASIC or javascript because modern C can be strict at times)
Try to collapse loops and statements to avoid need for curly brackets
Avoid == in various ways

Often these changes, especially ones that use multiply or divide, can be bad for performance on some systems. However the hope is an optimizing compiler can see past that and re-optimize the code to something that will run quickly on modern machines.

In the end I skipped some optimizations that would have worked in the old days but cause compiler warnings these days (mostly abusing orders of operations, or having single-statement code blocks triggering indent warnings if you put more on the same line).

I also skipped a few places where single-byte text constants could be changed to the equivalent two-digit numeric variant for aesthetics reasons.

Background

This is a variant of Starpath, a 64-byte MS-DOS/VGA demoscene demo by Hellmood released at Lovebyte 2025. This demo does raymarching and various clever things to get the animation, the gradient sky, and the stars all in a 64-byte executable.

Obviously this ends up being a lot larger than 64-bytes of 8086 assembly.

This version about 1/3 of the code is the actual ray-marching, and the latter 2/3 is code taking each frame and turning it into a sixel image.

I also made a version of this for the Apple II that fits in 256 bytes that won 2nd place at Outline 2025.

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