I don't know if it's a bug, an Easter egg or a feature, but then again with these Rageguys you newer know. Might just be a cat-thing. Anyway here goes;
First off - save your work (to not loose anything). Open a new painting and doodle away.
Press F11 (the F-key not to press).
Now everything kind of locks. In a strange way. As if the application interface is put on hold.
The cursor doesn't move when I move with mouse/tablet. But when I paint it re-focuses and does move. I can't select tools using the tools-palette, but keyboard shortcut works.
I can select drop-down menus (but I can not see when I do it). Tool properties and colour area works (also blinded).
It is kind of fun working blinded. Spurs you creativity in a whole new way – wouldn't you say?
Fortunately pressing F11 again will bring the application back to normal.