Tic-Tac-Swap

On your turn, you may either place a mark, swap symbols, or block one square so nobody can use it.

Using swap or block consumes your turn.

To block: click Block a square, then click any square on the board. Blocked squares show as ■ and cannot be used by anyone.

Existing marks do not change on swap; only player control of X/O flips.

Win condition is 5 in a row on a 10×10 board.