Toggling Glass Puzzle

There are N x N grids (cells) in this game.

You can choose the board size or mode from options menu.
Board can be of 2x2, 4x4, 6x6 or 8x8 size.

There are NxN upside down glasses intially on the board.

You can toggle the states of glasses (that is upside down glass to upright or upright glass to upside down) by selecting any (N*N-1) (i.e. 3, 15, 35 or 63 depending on board size) glasses.

*** Actually (N*N - 1) glasses are turned over in one move i.e. the state of the (N*N - 1) glasses are changed in one move.

Selected glass is highlighted by green boundary

Your task is to change the state of NxN upside down glasses to upright position.

In 'Voiced Mode' voice is enabled and in 'Non voiced Mode' voice is disabled.

Undo button restores the previous move.

Clear button clears the game board.

There are 2 modes (Voiced and Non voiced) of the game.
By default game is started in non voiced mode.

If you switch from one mode to another mode, game is restarted.

This game will enhance ones analytical, visual and problem solving skills.

This game is ABSOLUTELY FREE, contains NO IN APP PURCHASES and NO ADS.

In case of any bug please let me know through email.