Feedback From Client
The tool is great, I like it a lot. I like how simple it is to use. I would have suggestions for "Advanced" Options such as:

+Have more color options
+Be able to have a diamond shape to denote System action
+Add a legend
+More flexible grid snapping (place a card in between two parent cards)
+Change the size of the cards (or having a tag to put on a card)
+Change the font size, boldness, etc. of the card title
+Ability to not have the vertical and horizontal lines span the entire story map