Dunno. Half an hour with the Kindle before nodding off. Sleep like a bairn till the alarm goes off.

Mind you.. When my alarm clock gave up the ghost last year, I bought a stand and an app for my phone to be the bedside clock. That was a Samsung so only the pixels needed lit up, (OLED display.). I have since gone back to an iPhone and the whole thing is backlit, so the bedroom isn't as dark as it was.

Still sleep like a log though.