It definitely wasn't just you. Looking at some of the larger rooms in debug mode I was getting around 100 fps, which is a lot lower than it should be and could easily go under 60 on a less powerful machine. Thankfully, there was a pretty obvious optimisation I could make - after doing that it's getting around 5 times the fps. Could probably still optimise further, but it should at least address your issues.
I uploaded a new version with this fix. Since there's no visible difference I also added a version indicator. As of this update, the game is at version 0.1.3.0