Mega Hasan now runs windowed by default. You can toggle between full screen and windowed mode in settings.

Didn't feel like making an update just to explain that.. but just in case you're left handed and dont feel like using the arrow keys.. WASD works.

You may experience performance issues running your display on scaled mode.

If the frame rate is bad make sure your display settings look like this:

Please restart steam and reinstall game =)