Hello!
I like cats and I like cafes, so of course I had to test your game first ;)
I agree with another comment saying the game should have an easier-to-read font and a full screen option. I also think it would be nice to have a downloadable version later on.
About the game itself, I think the features currently here work fine. I couldn't do anything beside adopting new cat/collecting money but I guess it's because the game is still in development. To be noted though: for now, when we finish the demo, we can't try the game again, at least it doesn't work for me. I've reloaded the page and I am stuck on the Start/Quit menu which I can't interact with anymore.
For now the game involves mainly waiting and clicking on the cats. I suppose it is planned, but it would be nice to have more playability (aka more things to do inside the cafe) and a "twist": something that makes this game unique compared to other games of the same genre. I don't know what exactly, but maybe you already have an idea :)
Good luck for the future development!