In screen 1 the two cell cage with a clue of 2x has been selected.  The left hand cell has been selected for editing by touching it.  The only numbers that can satisfy this clue are 1 and 2 but we don’t know in which order yet.  We enter them into the two cells by tapping on the buttons at the bottom of the screen. 

Screen 2 shows the two cells that have been filled.  Notice that we entered 1 and 2 in order in the left hand cell and in reverse order in the next cell.  This is a mnemonic to remember that either the left or right pair is the correct solution.  Notice too that the cell clue and the digits appear across the top of the puzzle.  This is really handy for large puzzles with small cells on the screen.

We enter the digits 3 and 4 in the cage with a clue of 12x in screen 3.

In screen 4 we’ve entered a 1 in the bottom row of the third column.  This is because there is a 2 in the column and the digits 3 and 4 even though we don’t know their order yet.

We now look at the 6+ cage in the upper right hand corner in screen 5.  Only the digits 2 and 4 add to 6.  But the 2 can’t be entered in the top row since there is already a 2 in the 2x cage so that the 4 must be in the top row and the 2 in the second row.

The lower two empty cells in the right hand column have to be 1 and 3 since 4 and 2 are in the 6+ cage.  The 1 can’t be in the bottom row because there is already a 1 there so the 3 goes in the bottom row and the 1 above it as shown in screen 6.

The 4 that was entered into the top cell of the 6+ cage means that the top cell of the 12x cage must be a 3 not a 4.  Hence we touch the top cell and then tap on the 4 button along the bottom to remove it with the result shown in screen 7.

We then remove the 3 from the cell below it in screen 8.

In screen 9, the remaining 12x cage is filled with a 3 above a 4 since there is a 3 in the bottom row already.

The 6+ cage in the lower right hand corner is completed using logic similar to the 12x cage in screen 10.

The cell in the second column and second row can be filled in using the same logic as Sudoku.  The cells to the right contain 2 and 4 and the cells below contain 3 and 4.  The only remaining digit is 1 which is entered in screen 11.

The last empty cell must be 3 since 3 - 1 = 2 (screen 12).

The remaining cells in the original 2x cage are obviously now 1 and 2, solving the puzzle.

A this point you can start a new puzzle of the same or different size, change the puzzle options before starting a new puzzle, or clear the puzzle and start over if you like.