Being a fan of Zero Escape, I really had fun with the demo. The first room itself wasn't so difficult; however, I felt the size of the room was a little bit big, and I think implementing a point-and-click system on the objects in the room in addition to moving the character there and clicking it might be a good idea. Regardless, the clues in the room were helpful and fun to discover.
However, there was one part of the demo which I got stuck on- not because the puzzle was hard- but because there was a bug (no pun intended) when I tried checking the vents. For some reason, when I clicked on the vent that was supposed to have the key, there was no response, which made me unable to receive the key. It was only after I checked your walkthrough that I found it to be a bug. I didn't know what order of events lead to it, but once I switched up the order of clicking on the objects I finally was able to bypass the bug. Just letting you know.
Edit: Apparently once you click on the vent but instead of examining it you leave, you couldn't click on the vent anymore. That was how the bug happened.