about the coordinate talk...
i think a good way would be to select a key/corner and then have their position coordinates displayed and be able to edit them within kantan. Dragging around keys and placing them just by eyesight is a bit sloppy. I could see a Table DAT being used as well, especially if you want to move the keys through some remote control.
I think one way to enhance the dragging around keys or whole shapes would be to have a magnet/locking feature you can turn on, so edges or vertices can stick to a nearby edge/vertex if it's being dragged within the vicinity. but this may not be the simplest to implement nor is it necessary if you can directly edit coordinates.