You can get 1 bit transparency with 24 bit colour by simply picking a colour and using it as a mask - back in the day, I'd usually use pink - 255,0,255.

The fog could be done via greyscale, with something like:

col = 0,0,0,clamp(inp.r + sin(time) * 0.5,0,1)

The glow worm additive sprite could just be distance based in the shader.

(I didn't look at the code itself if it's available, so this is just my impression based on the supplied screenshot gif).