Wow ! 10 minutes for a feedback : this is amazing ! Thanks !
By looking at the code bits you pointed out, I found the problem :
I relied on the getElementProperty() function to get the bounds of the 'landing zone' rectangle area, instead of the getBoundingClientRect() function.
The first returns relative coordinates, the second returns absolute coordinates which are in the same referential as the hypeGestureXPosition and hypeGestureYPosition values.
Thank you again and keep it up - this is a marvelous and incredibly powerful software.