For my C++ class I had to make an unbeatable Tic-Tac-Toe game, so I decided to translate it from C++ to Scratch. This is the result, I used smart solving for all of the easy decisions and included all of the other variations. Just move your mouse to choose the square you want to play in and click to place your "o".
Thanks to benfire811 for: Unbeatable Tic-Tac-Toe (Original Project)