os x download and now when I try to sign in I get a white screen

So I downloaded the new os x Sierra for my macbook air 2012 and then restarted it. When the screen comes up to put in my password, I put it in and the screen goes white and black typed "computer language" comes across the screen for a few seconds and then disappears. A message saying there was an error and to restart then appears. And this cycle continues to happen once I restart it. Does this mean my laptop crashed? Is there anything I can do to fix this?