I made the main playing field the small size of 500 x 500 pixels in order to reduce the distance you have to move the mouse. Also, it meant I didn't have to manually implement graphics scaling, which PyGame didn't have support for until very recently. Hopefully nobody decides to play this on a 4K monitor, because it will be laughably tiny there.
It's funny being a developer, because you're shocked every time someone spends more than a minute on a level you can first try every time. I might nerf a few levels if I can get around to it.