Tic Tac Permanent

How to play
Click on one of the remaining empty spots.

Standard tic-tac-toe rounds:

Players each take turns placing blocks as indicated
The first player to get three of their own blocks in a row wins a round
The twist:

If a player wins a round, the losing player's last placed block stays for the rest of the game
If it is a draw, the second-to-last placed block similarly stays
The winning or last player gets to start first next round
If at the beginning of a round a player starts and the round can be won immediately due to staying blocks, they can win infinite rounds, and they have won the game.

Notice: The game is supposed to notice this endless victory condition and react, but it often doesn't. Not sure how to fix, so the problem stays.

Background & sou