Everything has been working fine for a while now. Today, I was watching a video on Youtube. I went full screen on the video, the screen started fluttering, looking like little red butterflies everywhere, the computer restarts, the Apple logo and status bar shows, then the screen just goes blank, like its stuck in the startup. I tried restarting, but the same thing happens. I dont know what else to do. Do I have to restore the machine from the beginning? If so, I might as well just go with High Sierra, since its compatible with my iMac, which is a late 09 i7, with 32GB ram, and a 1tb Samsung SSD, if that helps.