Thanks for playing! Hmm, about the bugs: I didn't notice this during development - do you mean that you can move your pieces to positions which have not been highlighted green?
Regarding the animations and sound effects: Yeah, that was a huge point I actually really wanted to address, but unfortunately I didn't have the time required to make them look / sound good. It's definitely on my to do list for future versions.
The moving / clicking the end turn button combination, if only the king is left will be removed soon. In the next version, the next turn will start automatically when your king is the last piece on the chessboard. Thanks for the feedback!