More context ... just got this computer about four months ago. Didn't drop it or anything. Didn't put anything heavy on it (just paper), and these strange lines appeared. I made an appointment at the Apple Store for next week, but today I noticed a "burn in" at the bottom of the screen. Where I was previously unable to see anything behind the lines, I can now see part of my browser, even after I move it. Very strange.
The build quality on this Mac is much poorer than usual. I've had Macs for 15 years and this is the first one with any issues (also the trackpad is cracked in the corner, again, without dropping the machine).