It only works if the starting point of a gesture is as expected. If I start a rectangle in the top right corner then it is characterized as a caret. Only a start in the top left results in a rectangle.
Right, this is expected. I would think of a "gesture" as a series of points over time (relative to the starting point) - it is path dependent, so a clockwise circle is recognized differently from a counter-clockwise circle.
The paper (citation 11 for the $1 version) goes into more detail. One neat feature is rotation invariance, where you can draw a tilted version and still have it be recognized.
I added a second rectangle as an example starting from a different point, and it never misrecognized any of my rectangles for carets or square brackets again.
Adding left and right parenthesis started messing up with the square brackets, but then I added a couple more of each square and round brackets and it worked perfectly.
Differentiating from lowercase y and g was next to impossible, though...
This varied a lot for me during testing - It looks like it's actually comparing rotations of the gesture to find a match
It would nail the zigzag and most of the star/box shapes even if I intentionally started in a different place (Very first thing I tested, I'm left handed and start characters/shapes in different places)
It did not handle shapes that are rotationally similar - ex: right square bracket starting from the bottom is always detected as left square bracket, probably because the gesture matches the left bracket, rotated 180 degrees.
It also flubs arrows going right to left (they always come up as v for me)
Palm apparently had to change graffiti later to use multiple strokes for some letters, as someone had a patent on letter-recognition via single-stroke letters.
