This Pi-powered protractor is intended to be used to calculate rotational angles in real time ... this is the sort of setup ...

Image caption, An obtuse angle is between 90° and 180°. Both of these angles are obtuse. Without using a protractor, a good estimate for the first angle is 135° because it is midway between 90 ...

Don’t you love it when the title track is the first one on the album? I had to single out this adjustable keyboard called the Protractor, because look at it! The whole thing moves, you know.