Seventh version uploaded

Uploaded the seventh version of my checkers.

Added:

* AI difficulty slider.

Overall, it turned out pretty nice, I think. There are still improvements to be made (see below), but I'm happy with how it is right now, so I decided that it's time to make this project public. Hope y'all have fun! ❤️
You can also check the code at https://github.com/FloraKardis/checkers, but I wouldn't recommend it.

Possible improvements:

* Better AI.

* Fix drag'n'drop.

* Fix ugly scaling/aliasing issues.

* Add sound effects.