Dr.Bob's Game of Memory on iOS
Dr.Bob's Game of Memory requires you to click on two buttons with the same "value", remembering what the button holds. After each two clicks, the 2 buttons are either disabled (when showing similar values) or their contents is hidden again.

This is a mind game, that can be played using a field from 2x3 to 8x12 buttons.

Initially, the playing field will be 2 buttons wide and 3 buttons high, but you can change that to a maximum of 8 buttons wide and 12 buttons high:

By default, the buttons will be filled with numbers (from 1 to the number of buttons divided by 2, so there will be two buttons for each individual number). Optionally, you can change the numbers to characters (a maximum of 48 unique characters: 26 letters, 10 digits and 12 other characters).

The objective is to click on two buttons with the same "value". Once you click on a button (the first of a pair), the value will be displayed. You should then click on another button, and hope (or remember) that it contains the same value:

When two buttons with the same "value" have been clicked, they will be disabled, and taken "out" of the game. When the two buttons do not show the same "value", they will show their value for a brief moment, and then display the "?" character again.

You can also swap the iPhone device, so the playing field will turn around (to a maximum of 8 wide and 12 high):