I am using GNOME Shell 3.18.5 with Ubuntu 16.04 LTS.
When I press the Ctrl key orange filled circles are starting to appear at the position of the cursor, getting bigger and bigger and loosing their alpha over time.
Well that is great, but why is it useful?
I have tried to figure it out, but I could not find anything assigned to the Ctrl key in Settings/Keyboard/Shortcuts. (but maybe I was not looking carefully enough)
So why is it useful and how can I remove/edit that shortcut if I want to?