I'm having a bit of a panic attack. Yesterday I upgraded to OS X Sierra from the App Store on my late 2014 Retina MacBook Pro. It restarted and brought me to my login page, where I entered my password. Then I got a bunch of black and white writing in the top-left corner of the login page, in the middle of which says "Mac OS version: Not yet set" Alright, obviously something happened with the update and I'll need to try booting up another way.... And here's where I'm stuck. My MacBook doesn't chime at startup (I can't remember if it ever did) and when I use any of the commands for safemode, etc, the screen stays black - no grey, no apple logo. Does anyone have a clue what might be happening? I'm not terrible with computers, but I've been trying to figure out how to boot in safemode (tried holding shift at startup) for hours. I can get to the login screen with Resart and Shutdown, so most of the tutorials I've seen don't really apply to me.