What's your browser? Have you tried refreshing the page? You can also share a screenshot here so we can take a look.
I'm using the Itch app on Windows
I've just tried the app. The game works fine. Isn't the window resizeable? What's your monitor resolution btw?
I tried to drag the edges but nothing happened and my resolution is 1366x768
This game's size is 600x800. I suggest you hide your taskbar when playing. Sorry I couldn't find any other solutions.
It's not problem at all, so long as I can play it :)