-{
- if (board->cells[move] == '_')
- {
- board->cells[move] = 'X';
- return(TTT_ERROR_NONE);
- }
+{
+ if (board->cells[move] != TTT_CELL_EMPTY)
+ return TTT_ERROR_NOT_VALID_MOVE;
+
+ board->cells[move] = board->current_player;
+
+ if (board->current_player == TTT_CELL_X)
+ board->current_player = TTT_CELL_O;