You just hit the back arrow to get to the level select then click back to meownu then exit.

A faster way to exit the game would be nice. Right now it takes about 4 clicks.

Why would you want to exit the game? You are just going to abandon all those cats? Surely you would not do something so cruel and terrible

I was a bit confused by that too at first. The arrow that takes you back looked like it would just go back to the previous puzzle, like browsing through a book or something

Try Alt + F4