I see what the problem is: I tried to launch the game from the itch.io app, which doesn't show this button because it has to know which file(s) belong to which operating system. Have you set the operating system for the file? Like this?
Whoops! Yep, that's what I was missing. I've set that up now. Seems to be working in the app now! Thanks for the screenshot - it was very helpful.
You're welcome :).
I just played the game, really liked the graphics, also very simple and fun concept. However, finding the last few cats took me a tad too long. Maybe you could add some kind of cat-transport mechanic to speed up the cats that have to walk from the other side of the map?