This is Tcl ("tickle").
She is a Pomeranian, possibly some sort of Pom mix but we just call her a Pom because she looks close enough.
When we moved to our new apartment, Tcl was absolutely fascinated and confused by the sliding glass doors that exit onto our patio.
At first, Tcl was a bit nervous. She didn't understand these strange clear doors and would often sit on the patio outside, while the door was open and I was calling her, not knowing what to do. She would stand up on her hind legs and extend her forelegs to where she thought the glass was, and then would fall forward adorably, and her front legs would hit the carpet. At that point, she knew it was safe, and would run into the room.
Eventually Tcl grew bold. She realized that she didn't have to go through this nonsense of standing up to try to touch the glass to make sure it wasn't there. So naturally, the next time we went to let her out, she barreled right into the glass door, and then staggered back, confused. After I opened the door, she watched her dear friend Grubby dash through and followed.
These doors are really strange. Sometimes they are there, and sometimes they aren't, and poor little Tcl can't tell which is which.
Since that incident, the little dog has still not quite figured out the doors, though I think she's getting closer. Being a person who tries to not have her silly pup run into glass doors (even if it is hilarious), I started to change up how I was letting them out. I decided not to open the blinds to see if that would help.
First time I did this, Tcl nosed the blinds aside, and ran right into the door.
Another time, I let Grubby out of his crate in the morning first AND left the blinds closed, in order to have him stop and wait by the door so Tcl could see and learn by example. Tcl shouldered him aside and ran through the blinds, right into the door.
She has done this no less than 10 times by now, though I think she might finally be getting it. At first I was starting to wonder if I'd need to get those things you put on big glass windows to prevent birds from flying into them, only putting them a foot above the ground at Tcl eye level. Thankfully it doesn't seem like this is necessary :)
So yeah. That is the saga of Tcl and the glass door.