maybe it was a little hard also to make the erase option for it see this answer - How to create a scratchcard - #10 by TimAi2 is still that is hard add a undo and redo option
maybe it was a little hard also to make the erase option for it see this answer - How to create a scratchcard - #10 by TimAi2 is still that is hard add a undo and redo option