Players Can Overwrite Each Other’s Moves

Title:
Players Can Overwrite Existing Moves

Description:
Currently, the game does not properly prevent players from overwriting each other's moves. Although there's a check to see if a space is already occupied, it does not handle the overwriting issue correctly, leading to moves being replaced.

Steps to Reproduce:

Start the game.
Player 1 makes a move.
Player 2 selects the same spot.
Observe that Player 2 is allowed to overwrite Player 1's move.
Expected Behavior:
Players should not be allowed to overwrite moves in occupied cells.

Suggested Fix:
Add a stronger check to ensure that once a move is made in a square, no player can overwrite it.

Look for the game board representation and the move validation logic. The issue is about preventing overwrites in occupied cells. Find where moves are processed and add a check that a cell is empty before allowing a move. Test by having two players attempt to play in the same spot.

Written by the indexing model from the issue text.