Really impressive graphically! Switching between two dimensions fits the theme perfectly, of course! I was a bit confused by the timer at first, since the format of the numbers made it seem like minutes and seconds, but the clue was in the title. :)
I found it was a lot safer not to move when a dimensional transition was upcoming, but that meant a lot of standing around waiting and I also had trouble figuring out where to go, I could see the levers I needed to press but not the routes to get to them. I'm also not super sure what the benefit of the portal was once I activated it.