Hi yerald
that PxPp30K.png is very creepy indeed, those metallic colors look like chrome or something.
speaking of chrome I tried Vervette on Opera, I got the same issue that happens on Firefox, when doing Ctrl Z the painting goes completely black.
I just have 3 addons on Firefox, I don't have any extension on Opera.
Also in both programs when doing the first strokes in the painting, a dot of painting appears in the center of the screen.
Only after several painstrokes (half drawing done) you can press Ctrl Z and the painting doesn't go black, but you go back almost half of what you have done.
avoiding Ctrl Z does it more difficult to draw than before, I almost scribbled this...
burning glass by
eduardobedoya, on Flickr
Hope this info helps.