@@ -46,7 +46,6 @@
 START_GAME: bool = False
 CHECK_FOR_WINNER: bool = False
 MAIN_DIAGONAL_IS_WINNER: bool = False
-CURENT_BOARD_WON: bool = False
 CONTINUE_WITH_NEXT_GAME: str = ''
 STEP_COUNTER: int = 0
 PLAYER_SWITCH = True
@@ -56,7 +55,7 @@
 PLAYER2_NAME: str = ''
 PLAYER2_MARKER: str = ''
 
-ROWS, COLS = (3, 3)
+ROWS, COLS = (3, 3)
 GAME_PROGRESS_ARRAY = [['' for i in range(COLS)] for j in range(ROWS)]
 GAME_PROGRESS_ARRAY = np.array(GAME_PROGRESS_ARRAY, dtype=str)
 # WINNING_PATTERNS: list = [['00', '10', '20'], ['01', '11', '21'], ['02', '12', '22'], # rows
@@ -69,28 +68,46 @@ def split(word):
 
 def progress_game(key: str, player_marker: str):
 '''populated the 'GAME_PROGRESS_ARRAY' and
-checks for is winning condition.'''
+checks for is winning condition.
+
+PARAMS:
+1. key - the button element in the grid that was clicked.
+
+2. player_marker - the marker of the current player.
+
+RETURNS:
+continue_with_next_game - 'Yes' / 'No' indicator from the user action
+whether to continue with the same players.
+'''
 
 global GAME_PROGRESS_ARRAY
-global CURENT_BOARD_WON
 
 continue_with_next_game: str = ''
 
 row, column = split(key)
 GAME_PROGRESS_ARRAY[row][column] = player_marker
 
+# check if we have a winner in the current state of the board.
 if CHECK_FOR_WINNER:
 game_won, winning_marker = is_winning()
 if game_won:
-CURENT_BOARD_WON = True
 continue_with_next_game = display_winner_and_continue(winning_marker=winning_marker)
 
 return continue_with_next_game
 
 def is_row_column_diagonal_complete(row_col_num: int = -1, is_row: bool = True,
 is_diagonal: bool = False):
 '''checks if the given row or column is complete
-to proceed with a winner.'''
+to proceed with a winner.
+
+PARAMS:
+1. row_col_num - the row/column index to check if the row/columns is complete.
+2. is_row: True if a ROW needs to be checked for completion else FALSE for a column.
+3. is_diagonal: True is any of the diagonal needs to be checked for completion.
+
+RETURNS:
+is_complete: BOOLEAN FLAG to indicate of the row/column/diagonal is complete.
+'''
 is_complete: bool = False
 
 if is_diagonal is False and row_col_num != -1:
@@ -117,10 +134,22 @@ def is_row_column_diagonal_complete(row_col_num: int = -1, is_row: bool = True,
 
 return is_complete
 
-
-def mark_the_winner(row_is_winner: bool, row_column_index: int = -1, diagonal_is_winner: bool = False):
+def mark_the_winner(row_is_winner: bool, row_column_index: int = -1,
+ diagonal_is_winner: bool = False):
 '''marks the winner row/column by updating
-the button row/column.'''
+the button row/column. The button image background
+changes to red to mark the winning sequence.
+
+PARAMS:
+1. row_is_winner - Is the winner found in a ROW wise sequence.
+TRUE for a row & FALSE incase the winner is a column.
+
+2. row_column_index - The winning row/column index.
+This default value is -1 to indicate the winner being found
+in one of the diagonals.
+
+3. diagonal_is_winner - Is the winner found in one of the diagonals.
+'''
 
 if not diagonal_is_winner and row_column_index != -1:
 if row_is_winner:
@@ -203,7 +232,11 @@ def is_winning():
 return False, ''
 
 def display_winner_and_continue(winning_marker: str):
-'''display the winner of the current board.'''
+'''display the winner of the current board.
+
+PARAMS:
+1. winning_marker - the marker that won the current board.
+'''
 
 if winning_marker == PLAYER1_MARKER:
 popup_result = sg.PopupYesNo('The Winner is ' + PLAYER1_NAME + '.\nDo you want to play another game with the current players?',
@@ -218,6 +251,7 @@ def display_winner_and_continue(winning_marker: str):
 
 def init_game_window():
 '''Initializes and creates the game options window.'''
+
 init_game_layout = [[sg.Text('Player 1 Name: ', size=(12, 1)),
 sg.InputText('', key='-P1_NAME-')],
 [sg.Text('Player 2 Name: ', size=(12, 1)),
@@ -239,18 +273,36 @@ def reset_game_board():
 global STEP_COUNTER
 global CONTINUE_WITH_NEXT_GAME
 global CHECK_FOR_WINNER
-global CURENT_BOARD_WON
 global GAME_BOARD
 global PLAYER_SWITCH
+global MAIN_DIAGONAL_IS_WINNER
 
 GAME_BOARD = initialize_game_board()
 GAME_PROGRESS_ARRAY = [['' for i in range(COLS)] for j in range(ROWS)]
 GAME_PROGRESS_ARRAY = np.array(GAME_PROGRESS_ARRAY, dtype=str)
 STEP_COUNTER = 0
 CHECK_FOR_WINNER = False
 CONTINUE_WITH_NEXT_GAME = ''
-CURENT_BOARD_WON = False
 PLAYER_SWITCH = True
+MAIN_DIAGONAL_IS_WINNER = False
+
+def start_next_session(user_choice: str):
+
+'''starts the next session as per the user choice.
+YES - retain the players and reset the board state.
+NO - return to the game init dialog to start over with new set of players.'''
+
+global INIT_WINDOW
+global GAME_BOARD
+
+if user_choice == 'Yes':
+# retain the players and reset the board state.
+GAME_BOARD.Close()
+reset_game_board()
+elif user_choice == 'No':
+# return to the game init dialog to start over with new set of players.
+GAME_BOARD.Close()
+INIT_WINDOW = init_game_window()
 
 def initialize_game_board():
 '''initialize the game board.'''
@@ -291,6 +343,7 @@ def initialize_game_board():
 
 if EVENT == '-START-' and not GAME_BOARD:
 
+# player name validation. Valid names required.
 if VALUES['-P1_NAME-'] == '' and VALUES['-P2_NAME-'] == '':
 sg.popup_ok("Error initializing players name. Enter both the players name before proceeding.",
 title='Tic Tac Toe', icon=GAME_ICON)
@@ -313,14 +366,16 @@ def initialize_game_board():
 INIT_WINDOW.close()
 GAME_BOARD = initialize_game_board()
 
-if WINDOW == GAME_BOARD and (EVENT in ('WIN_CLOSE', 'Exit')):
+if WINDOW == GAME_BOARD and (EVENT in ('WIN_CLOSE', '-EXIT-')):
 GAME_BOARD.close()
 GAME_BOARD = None
 INIT_WINDOW = init_game_window()
 
-if START_GAME:
+# We do not want to execute the progress logic in case
+# of the reset event.
+if START_GAME and EVENT != '-RESET-':
 
-if EVENT not in ('-START-', 'WIN_CLOSE'):
+if EVENT not in ('-START-', 'WIN_CLOSE', '-EXIT-'):
 CURRENT_MARKER = GAME_BOARD.Element(EVENT).get_text()
 GAME_BOARD.Element(EVENT).update(PLAYER1_MARKER if CURRENT_MARKER == ' ' and\
 PLAYER_SWITCH is True else PLAYER2_MARKER if CURRENT_MARKER == ' ' and\
@@ -341,6 +396,7 @@ def initialize_game_board():
 GAME_BOARD.Element('-P1-').update(text_color='white')
 GAME_BOARD.Element('-P2-').update(text_color='darkblue')
 
+# update the button images as per the current players marker.
 if PLAYER1_MARKER == 'X':
 GAME_BOARD.Element(EVENT).update(image_filename=X_IMAGE)
 else:
@@ -349,12 +405,10 @@ def initialize_game_board():
 GAME_BOARD.Element(EVENT).update(disabled=True)
 
 CONTINUE_WITH_NEXT_GAME = progress_game(EVENT, PLAYER1_MARKER)
-if CONTINUE_WITH_NEXT_GAME == 'Yes':
-GAME_BOARD.Close()
-reset_game_board()
-elif CONTINUE_WITH_NEXT_GAME == 'No':
-GAME_BOARD.Close()
-INIT_WINDOW = init_game_window()
+
+# start with the same players or new game
+# session with different players
+start_next_session(CONTINUE_WITH_NEXT_GAME)
 
 elif GAME_BOARD.Element(EVENT).get_text() == PLAYER2_MARKER:
 # increase the step counter.
@@ -365,6 +419,7 @@ def initialize_game_board():
 GAME_BOARD.Element('-P1-').update(text_color='darkblue')
 GAME_BOARD.Element('-P2-').update(text_color='white')
 
+# update the button images as per the current players marker.
 if PLAYER2_MARKER == 'X':
 GAME_BOARD.Element(EVENT).update(image_filename=X_IMAGE)
 else:
@@ -373,18 +428,20 @@ def initialize_game_board():
 GAME_BOARD.Element(EVENT).update(disabled=True)
 
 CONTINUE_WITH_NEXT_GAME = progress_game(EVENT, PLAYER2_MARKER)
-if CONTINUE_WITH_NEXT_GAME == 'Yes':
-GAME_BOARD.Close()
-reset_game_board()
-elif CONTINUE_WITH_NEXT_GAME == 'No':
-GAME_BOARD.Close()
-INIT_WINDOW = init_game_window()
+
+# start with the same players or new game
+# session with different players
+start_next_session(CONTINUE_WITH_NEXT_GAME)
 
 # The minimum number of steps required
 # to win the game board is 5.
 if STEP_COUNTER == 4:
 CHECK_FOR_WINNER = True
 
-if EVENT == '-RESET-':
-GAME_BOARD.Close()
-reset_game_board()
+if EVENT == '-RESET-' and WINDOW == GAME_BOARD:
+# reset the current board state.
+RESET_GAME = sg.popup_yes_no('Are you sure you want to reset the current board?',
+title='Game Reset', icon=GAME_ICON, grab_anywhere=True)
+if RESET_GAME == 'Yes':
+GAME_BOARD.Close()
+reset_game_board()