Don't hold Ctrl Z, haha... just hit Z once. Funny that it's so fickle on your browser? Which one are you using? I still recommend Chrome!
Undo has (again) 20 slots and will toggle through them in either direction (undo and redo). If the buffer is empty, it will be black. It's more of an "effect", than a "defect", hahaha... but I'll make this nicer in the full version!
The tiny sliders in the color GUI next to RANDOM HUE are (rate) and (range). I thought, I wrote about it in the "Manual" on the first post? Didn't I?
The noise is like a stencil and stays in place. That means, it won't move with the brush, but rather acts similar to a canvas texture. As a result, if you use strong enough DETAIL (the second noise slider) and/or high enough Contrast (third slider), you may end up having spots on the canvas, where the brush won't get to unless you offset the noise, or lower the DETAIL or change the SCALE (first slider).
The sliders have labels. The only ones without labels are on the noise and the random hue.

Just have a brief look at the first post of this thread, which acts as a MANUAL and you'll find out all there is to be found out!

Thanks for trying, though, that's great!
