Tic-Tac-Toe Variants

What if each square on a Tic-Tac-Toe board had another Tic-Tac-Toe board inside of it?

Imagine Tic-Tac-Toe if both players could play as both Xs and Os!

Imagine Tic-Tac-Toe, but both players can both play as both X and O throughout the whole game!

Want to take Tic-Tac-Toe to the next level!? Imagine a 15×15 board. You must get five-in-a-row. You cannot get six-in-a-row. That’s Gomoku!

What if you only played Tic-Tac-Toe with Xs and you could play on multiple boards?