Jolt Country

Robert Stickles (sutekh@feldspar.com) explained it very well like this:
The 3-D imager spins a disk which is 1/2 black and ]
1/2 colored bands
that radiate from the centre (Usually red, green and blue) between your
eyes and the vectrex screen. The Vectrex is synchronized to the
rotation of the disk (or vice versa) and draws vectors corresponding to
a particular color and/or a particular eye. Therefore only one eye will
see the vectrex screen and its associated images (or color) at any one
time while the other will see nothing.

A single object that does not lie on the plane of the monitor (i.e. in
front of or into the monitor) is drawn at least twice to provide
information for each eye. The distance between the duplicate images and
whether the right eye image or the left eye image is drawn first will
determine where the object will appear to "be" in 3-D space. The 3-D
illusion is also enhanced by adjusting the brightness of the object
(dimming objects in the background). Spinning the disk at a high enough
speed will fool your eyes/brain into thinking that the multiple images
it's seeing are two different views of the same object, and voila!
Instant 3-D and color.

As we all know, the very first Vectrex units were shipped with a flawed
version of Minestorm. Evidently nobody ever though that any player
could ever get to, let alone survive wave 12 so they only included data
for 12 waves. Predictably, most players found that their game crashed
after wave 12 (the "wave 13" bug) because the software indexed off the
end of the table which contains the information about what items were to
exist on each wave. It reads in garbage which usually causes the game
to crash.