Black screen after High Sierra update, MacBook Pro w/user-installed SSD Ran the High Sierra updater, walked away as it ran. Came back after 40 minutes or so to find a black screen. That’s it.

Keyboard was backlit, and pressing keys (spacebar, arrows, esc/fn/command/option) don’t wake things up. If I leave it alone for a while, the keyboard goes dark, but a key press lights it back up...but still no screen. 

It’s a late-2011 15” Core i7, 2.2 ghz, with 4gb RAM and a hard drive upgraded from 500gb rotating media to 1tb SSD (Samsung 850 EVO).

(As a side note, my late-2014 Mac Mini updated just fine.)

Any thoughts on how to proceed?

UPDATE: a pal suggested shutting the lid, waiting 30 seconds, then re-opening the lid. That powered it down...somehow. Then I held down the power button till it restarted, and all is (now, thankfully) well. Hope this helps someone out.
Mikey_S has answered the question on his/her own:


  a pal suggested shutting the lid, waiting 30 seconds, then re-opening
  the lid. That powered it down...somehow. Then I held down the power
  button till it restarted, and all is (now, thankfully) well. Hope this
  helps someone out.