Hey,
We added the fullscreen button itch.io provides, which will let you play. The game does not stretch, but you can see the full window as it is supposed to be. We don't know why it is causing some people the same problem. It was too much stress yesterday trying to build in time :'D
The game files are not changed, we only added the fullscreen option from the page.
Sorry for the inconvenience, hope you can play and have fun!
Tell us if you do so :D