I finally corrected the "bug" that was bugging me...LOL!! It's was only a small coding error that i forgot to add (DOH!), but now i can begin to upgrade all the rest of the games.
But before doing that, here is the latest "OdySim Tennis" (or in the menu on the right side) version which is in sync with the latest LÖVE version (0.10.1). And i added a new feature thanks to Brian (aka CN10) which you can now decrease or increase the AI level (with buttons "9" and "0") so this way you can "beat" the AI, because before this version the AI was unbeatable. And also, the "F9" button now works (you can switch OFF or ON the overlay).
So download this new version and send me (see the read-me text for my e-mail address) or leave a comment if there is any bug(s) or error(s) or to say what you think of it.