Hello again! I think I know what resolution causes the problem. Looks like the game UI still can't properly scale with the monitor with a 16:10 aspect ratio and only supports a 16:9 aspect ratio. I don't know if it's possible to change your monitor resolution to a 16:9 aspect ratio via your computer control panel, but if you could the game should look normal.
I'm sorry, I can no longer give any updates for the Demo version, but I'll try to sort out this problem on the finished game.
Still, thank you for the bug report!