iMac 2011 screen is shacking after using a app Affinity in full screen
hi
I have a iMac 2011 and today my screen is going crazy after using a app affinity designer.
FIrst, frozen with tthat round icon
Second, the screen shacking with light lines
and I can't turn off with keyboard, I need to turn off on power button.
iMac, OS X Yosemite (10.10.1), 2011