The Imlac PDS-1 desk sized computer with vector processor controlled calligraphic display.
The Imlac was the first graphical machine that the university could afford to buy more than one at a time. They bought three.
Maze used a data structure that could be interpreted by two processors at once. An automatic solver could solve a dense puzzel in 15 to 30 seconds, or, several times a second when it wasn't synchronized to the display.
Light Pen tracking required drawing something on the screen that could be seen when drawn. Usually we drew boxes. But one implementation came by that drew a tight little circle. It modeled hand dynamics and when this failed to predict the proper circle placement it threw a scattering of dot up in the vicinity until it found its place again.
Hangman played a graphical version of the child's game by emitting canned strings interpreted by Bill Croft's graphically augmented terminal program. This was coded in PROCSY, a remote batch control language never meant for graphics.
NSD Editor was a graphical program editor coded in fortran and cross-compiled on a DEC PDP-11 that shared mechanical engineering's graphics lab.