I've been modeling for just under a year, and I hit random keys by mistake. This time, I can't figure out which one I hit. In modeling some stairs, I accidentally messed up the steps.
I was trying to hide the steps so that I could get to the supports easier, and after modeling on the supports, I unhid the steps, and they looked smooth-shaded.
With the black smudges, it also looks like it could be rendered, but that doesn't make sense to me (Could be possible)
I tried to shade flat in object, and edit mode, though that didn't help matters.
What on earth could I have done? I can't (I could, but would like to figure it out at this point) undo to the point that I did it, and really need to figure out what happened.
Thank you very much for your help!
EDIT: Blender version 2.93.1 - Here's the blend file. Thank you. Also, another picture to help drive the issue home. The stairs look smooth-shaded, but they're not supposed to be smooth. Trying to smooth flat results in no change.
EDIT 2.0 (Fix) - The issue was that I hit the hotkey for "Auto Smooth" This is different than "Shade-Smooth", so there was no effect in changing to Shade-Flat.
Select your model in either object or edit mode. And open Object Data Properties on the right. Scroll down to Normals, and uncheck "Auto Smooth"
A suggested topic on the right is what ultimately led me to the discovery. Thanks to everyone who helped!