Shader: Pixel Dominance

Another shader toy:

So, I wondered what would happen if set up a shader where I flood filled pixels based on a function where every colour beats half of the colour space. I also introduce one new random pixel per frame. I quite like the intricate patterns that show up after a few minutes. Not what I would have expected. This is the function I used to decide which pixel won:

X and Y are R+G+B for the two pixels being compared.