Game & Watch games do have instructions written in the manual that comes with the game.
Here is a manual example of a homebrew game of mine.
You don't need to make a manual of course, you can just write it on this page, if you want. I guess more G&W fans would want to play your game, if you do.
About the gameplay :
I think it would be nice the cat, as second player, could miss too, @ every 3 failed grab attempts for example. Else the second player can never loose, which can not be the purpose, i guess.
When the mouse is on the top shelf, can the cat grab it too? Couldn't really tell, because i didn't see any grab animation.
I apologise if i sound a bit negative, that's not the purpose of my comments. i just like to see more people apreciate your nice work.