This illustration shows the board after you have clicked on the number 1 at the top right of the board...OR...after you have hit the 1 key either on the main keyboard or on the number pad...OR...after you have clicked on the number 1 in one of the board squares.
This is what the board will look like...briefly...after you have chosen a square into which to place the number 1. After a fraction of a second, both white-on-black numbers will revert back to black-on-white, as shown below.
You could also hit the backspace key to get the result shown on the right below.
Note that the program will not allow you to enter a number in a square where it obviously does not go...for example, on top of an existing number, or in a row, column or box which already contains the number 1. That's all there is to entering...or deleting...moves.
If you hit the wrong number by mistake, highlighting it on the left, then hitting any number before you try to enter it on the left will erase that entry and allow you to start over for that move.
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This illustration shows the board after you have clicked on the number 1 at the top right of the board...OR...after you have hit the 1 key either on the main keyboard or on the number pad...OR...after you have clicked on the number 1 in one of the board squares.
This is what the board will look like...briefly...after you have chosen a square into which to place the number 1. After a fraction of a second, both white-on-black numbers will revert back to black-on-white, as shown below.
You could also hit the backspace key to get the result shown on the right below.