Thank you so much for playing our game and for taking time to send us feedback.
It would be good to know what graphics card and browser you are using. We had some issues with performance, which hopefully will be addressed in the new patch coming in a couple of days.
When it comes to full-screen closing, we will look into it. The game was always intended to be downloadable and the web version is more of a bonus that we added and need to make sure we can optimise controllers and performance for it better.
Thank you